B
REVIEW OF
LITERATURE
9
2. REVIEW OF LITERATURE
Presently, urban Indian population is going through a phase of dietary transition;
people have started opting for commercially available packaged foods or quick
homemade foods (Misra et al, 2009a). These snacks often regarded as “comfort/
convenience/ ready to eat foods” are quickly prepared or are available
commercially anywhere anytime. Of all the countries, India is one of the largest
snack markets and people consume more than 400,000 tonnes of snacks every
year. These so called “comfort foods” include fried foods that are high in energy
(particularly fats) and low in other nutrients (Agrawal et al, 2008). These faulty
dietary habits have contributed to increased incidence of lifestyle related non
communicable diseases including obesity, the metabolic syndrome, type 2
diabetes mellitus (T2DM) and cardiovascular diseases (Misra and Khurana, 2008;
Bhardwaj et al, 2008). Figure 2.1 highlights the relationship between nutrition
transition, urbanization, and the rise in obesity, the metabolic syndrome and
T2DM in developing countries including India (Misra et al, 2010). Most of these
commercially prepared foods contain Trans fatty acids, also called Trans Fatty
acids (TFA), are coming from Vanaspati - the partially hydrogenated vegetable
oils, which is used for its low cost and longer shelf life. Also, due to ignorance or
to save resources, the oil after frying is used repeatedly not only at commercial
outlets but even at household level, leading to the generation of free radicals
(Martin et al, 2007; Donnelly and Robinson, 1995) and reportedly some TFAs,
making the oil unfit for consumption.
The developing world, especially the South Asian countries are facing the menace
of TFAs. In this region, the use of partially hydrogenated vegetable oils (vanaspati
ghee) in deep-fat frying of culinary items, such as samosa, paratha, poori/
bhatura, tikkie etc, results in increased consumption of TFAs (Butt et al, 2009). In
India, due to ignorance among consumers, scarcity of data on the TFA content of
fried/ baked foods, their formation in re-heated oils or their consumption through
Indian dietaries, no stringent guidelines to curb their intake, and resulting in
10
harmful effects of high TFA consumption. Presently the limited data available in
India on the TFA content of food articles are calculated on the basis of TFAs
present in the raw ingredients and not on the laboratory analysis of cooked food
items (Agrawal et al, 2008). Most importantly, Indian consumer today is
incognizant of the amount of TFAs present in such foods and lacks the
understanding of the actual amount of TFAs (s)he is consuming during the day.
The population in general is ignorant of the adverse effects of TFAs on various
body organs including heart.
*: Pattern 3 may be seen at different rates of progression in different developing countries, # : Likely to
affect all socio-economic strata
Figure 2.1: Relationship between nutrition transition, urbanization, and the rise in
obesity and the metabolic syndrome in developing countries (Source: Misra et al,
2010)
Pattern 1:
Diets rich in carbohydrates, fiber, low in fats, saturated
fats, high activity profile & lean body phenotype
Pattern 2:
Famine-like situation, low calorie, low protein and fat
diets, low body fat and fat-free mass, growth retardation
Improved food supply, Increased food availability (longer shelf life, 24-
hour supermarkets), Competitive prices of energy dense foods
Pattern 5:
Increase intake of; improved quality of fat,
green leafy vegetables, and fiber; decreased
intake of refined carbohydrates, energy-
dense foods
Pattern 4 #:
Rise of obesity, the metabolic
syndrome and type 2 diabetes
mellitus (T2DM)
Pattern 3 *:
Decreasing food scarcity and
famine, labor intensive work
Increased intake of fat, salt and sugar
Dietary liberalization and “westernization”
Demographic Changes:
Rural-urban migration,
increasing elderly
population, Mechanization
Economic Changes:
Urbanization, open
market economy,
increasing affluence
11
Also, since the quality of oil degrades during heat treatment (both at the industrial
level/ large scale cooking and at home) it is necessary to estimate the TFA content
of the fat subjected to heating/ repeated heating. Thus, research on TFAs and
education of the masses, particularly the women is of utmost importance, given
the alarmingly rising trend of diabetes, cardiovascular diseases and the metabolic
syndrome in India.
2.1 DIETARY FATS AND FATTY ACIDS
Fats and oils are the major components of our diet. In addition to being a
concentrated source of energy, dietary fats have several physiological functions
such as providing essential fatty acids, facilitating the delivery of fat soluble
vitamins, improving texture and palatability of the foods as well as contributing to
the satiety. The nutritional and health benefits of dietary fats depend on the type of
fatty acids and the minor components such as tocopherols, tocotrienols,
phytosterols etc present in the non-glyceride fraction of the vegetable oils.
Therefore, the current recommendations on dietary fats are now laying emphasis
on the type of fat rather than on the quantity alone. The pathogenesis of several
diet related chronic diseases such as cardiovascular diseases, type 2 diabetes
mellitus, hypertension, inflammatory bowel disease, certain types of cancers,
neurological and neuropsychiatric disorders are directly or indirectly related to
dietary fats.
Fats, oils or lipids consist of a large number of organic compounds including fatty
acids, monoacylglycerols, diacylglycerols, triacylglycerols (TG), phospholipids
(PL), eicosanoids, docosanoids, resolvins, sterols, sterol esters, carotenoids,
retinol, tocopherol, tocotrienols, fatty alcohols, hydrocarbons and wax esters
(FAO, 2008). Classically, lipids were defined as substances that are soluble in
organic solvents. This however, is a loose definition and could include a number
of non-lipid organic compounds. A chemically novel definition and
comprehensive system of classification of lipids were proposed in 2005 which
defines lipids as “small hydrophobic or amphipathic (or amphiphilic) molecules
that may originate entirely or in part by condensations of thioesters and/or
12
isoprene units”. The proposed lipid classification system enables the cataloguing
of lipids and their properties in a way that is compatible with other
macromolecular data bases. Using this approach, lipids from biological tissues
have been divided into 8 categories (Table 2.1) containing distinct classes and
subclasses of molecules (FAO, 2008; Fahy et al, 2005).
Table 2.1: Categories of lipid with typical examples
(FAO, 2008)
Category Example Category Example
Fatty acids Oleic acid Sterol lipids Cholesterol
Glycerolipids Triacylglycerol Prenol lipids Farnesol
Glycerophospholipids Phosphatidylcholine
Saccharolipids UDP-3-0-(3hydroxy-
tetradecanoyl)-N-
acetylglucosamine
Sphingolipids Sphingosine Polyketides Aflatoxin
2.1.1 Fats and Fatty Acids
Chemically, fatty acid is a carboxylic acid with an aliphatic tail (chain). These are
a diverse group of molecules, characterized by a repeating series of methylene
groups that impart hydrophobic character. The fatty acid structure represents the
major lipid building block of complex lipids and therefore, is one of the most
fundamental categories of biological lipids. This lipid class includes the various
types of fatty acids, eicosanoids, fatty alcohols, fatty aldehydes, fatty esters, fatty
amides, fatty ethers and hydrocarbons. Many members of this category,
especially the eicosanoids, derived from n-6 and n-3 polyunsaturated fatty acids
(PUFAs), have distinct biological activities. The fatty acids present in various
lipid molecules are the major components of dietary fats. In the body, they are
incorporated in blood lipids, in fats deposits and in structural lipids in biological
membranes.
Dietary fatty acids are derived from acylglycerols, free fatty acids, phospholipids
and sterol esters. Of these, triglycerides (TG) are the main sources. The physical
and chemical characteristics as well as the health and nutritional effects of dietary
fatty acids are influenced greatly by the kinds and proportions of the component
13
fatty acids. The predominant fatty acids are straight chain, can be saturated or
unsaturated (containing one or more carbon-carbon double bonds) with an even
number of carbon atoms. Fatty acids containing 1 double bond are called
‘monounsaturated fatty acids’ (MUFA) and those with two or more double bonds
are called ‘polyunsaturated fatty acids’ (PUFA). A cis configuration means that
the hydrogen atoms at the double bonds are on the same side of the chain while in
a trans configuration they are on opposite sides. In almost all the naturally
occurring PUFAs the double bond exists in a methylene (CH2) interrupted pattern
i.e. the double bonds are in non-conjugated position. In most of the naturally
occurring unsaturated fatty acids, the double bonds are in the cis configuration and
are typically positioned at the 3rd
(ω3/ n-3), 6th
(ω6/ n-6), or 9th
(ω9/ n-9) carbon
atom from the terminal methyl group.
2.1.2 Nomenclature of fatty Acids
There are a number of systems of nomenclature for fatty acids, but some do not
provide sufficient information on their structure. A chemical name must describe
the chemical structure unambiguously. The systematic nomenclature
recommended by the International Union of Pure and Applied Chemistry
(IUPAC-IUB Commission on Nomenclature, 1978) names the fatty acids on the
basis of the number of carbon atoms as well as the number and position of
unsaturation relative to the carboxyl group (Table 2.2). In addition the
configuration of double bonds, location of branched chains and hetero atoms and
other structural features are also specified. The carbon atom of the carboxyl group
is considered to be first and the carbons in the fatty acid chain are numbered
consequently from the carboxylic carbon (FAO, 2008).
By convention, a specific double bond in a chain is identified by the lower number
of the two carbons it joins. The double bonds are labeled with Z or E where
appropriate but are very often replaced by the terms cis and trans, respectively.
For example, the systematic name of linoleic acid (LA) is “Z-9, Z-12-
octadecadienoic acid” or “cis-9, cis-12-octadecadienoic acid”. Although the
IUPAC nomenclature is precise and technically clear, the fatty acid names are too
14
long and therefore, for convenience, ‘trivial’ or historical names and shorthand
notations are frequently used in scientific writings. There are several shorthand
notations for dietary fatty acids, but all of them adopt the form C: D, where C is
the number of carbon atoms and D is the number of double bonds in the carbon
chain.
Biochemists and nutritionists very often use the “n minus” system of notation for
naturally occurring cis unsaturated fatty acids. The term “n minus” refers to the
position of the double bond of the fatty acid closest to the methyl end of the
molecule. This system defines easily the different metabolic series, such asn-9, n-
6 and n-3, etc. The “n minus” system is applicable only to cis unsaturated fatty
acids and to those cis polyunsaturated fatty acids whose double bonds are
arranged in a methylene interrupted manner. LA, which has its second double
bond located at6 carbons from the methyl end, is abbreviated to 18:2n-6. The “n
minus” system is also referred to as the omega system. (IUPAC-IUB Commission
on Nomenclature, 1978).
Another system widely used is the delta (Δ) system, in which the classification is
based on the number of carbon atoms interposed between the carboxyl carbon and
the nearest double bond to the carboxylic group. This system specifies the position
of all the double bonds as well as their cis/trans configuration. It is applicable to a
large number of fatty acids, except those with branched chains, hetero atoms,
triple bonds and other fatty acids with unusual structural features. According to
the delta system, the shorthand notation for LA is “cis-Δ9, cis-Δ12-18:2”. For
convenience, it could be expressed as “cis,cis-Δ9,Δ12-18:2”. In some scientific
papers, authors drop the “Δ” notation and write it simply as “cis-9,cis-12-18:2” or
“9c,12c-18:2”.
In edible fats/ oils, the fatty acids are commonly classified as per the length of
carbon chain and their degree of saturation/ unsaturation. Fatty acids vary in
carbon chain length ranging from 2 to 80 carbons, but are typically present in food
as 14, 16, 18, 20 and 22 carbon atom chains. Fats varying in fatty acid chain
lengths are metabolized differently.
15
Based on the length of carbon chain, fatty acids are classified as short chain,
medium chain or long chain fatty acids.
Short chain fatty acids contain 2-8 carbon atoms, such as butyric acid (C-
4) or propionic acid (C-3). They are formed in the gut when
polysaccharides are fermented by the anaerobic bacteria present in the
large intestine. Short-chain fatty acids, just as medium-chain fatty acids,
are taken up directly to the portal vein during lipid digestion (Bird et al,
2000).
Medium chain fatty acids contain 6 to 12 carbons atoms. Triglycerides
containing medium chain fatty acids are known as Medium Chain
Triglycerides (MCTs). These are medium chain fatty acid esters of
glycerol. They are directly absorbed into the portal circulation and
transported to the liver for rapid oxidation (Scalfi et al, 1991). MCTs
passively diffuse from the GI tract to the portal system without requiring
any modification like long-chain fatty acids. In addition, MCTs do not
require bile salts for digestion. Patients suffering from malnutrition or
malabsorption syndromes are treated with MCTs because they do not
require energy for absorption, utilization, or storage. Coconut oil is
composed of approximately 66% medium-chain triglycerides. Other rich
sources of MCTs include palm kernel oils and camphor tree drupes.
Long chain fatty acids contain 12 or more carbon atoms. However, this
term is often used to describe the longer chain fatty acids that contain more
than 20 carbon atoms, which may also be referred to as very long chain
fatty acids. Long chain fatty acids are first acted upon by bile salts leading
to their emulsification and later these are absorbed into the lymphatic
system.
Based on the saturation/ unsaturation fatty acids are classified as saturated and
unsaturated fatty acids.
Saturated Fatty Acids (SFAs) contain only single (carbon-to-carbon)
bonds. Most of the SFAs occurring in nature have unbranched structures
and an even number of carbon atoms (Table 2.3). They have the general
16
formula R-COOH; and are represented by the number of carbon atoms
with zero double bonds (stearic acid; C18:0). SFAs are chemically the
least reactive and therefore they are more stable and have a longer shelf
life than the unsaturated fatty acids. The melting point of SFAs increases
with the chain length. Decanoic and longer chain fatty acids are solid at
normal room temperature. The SFAs are further classified into 4
subclasses according to chain lengths: short, medium, long and very long.
Since various definitions are used in the literature for the SFA subclasses
the FAO (2008) recognized that there is a need for universal definitions
and recommends the following:
Short-chain fatty acids: between 3 and 7 carbon atoms e.g. Butyric acid
(4: 0) and caproic acid (6: 0)
Medium-chain fatty acids: between 8 and 13 carbon atoms e.g.
Caprylic acid (8: 0), capric acid (10: 0) and lauric acid (12: 0)
Long-chain fatty acids: between 14 and 20 carbon atoms e.g. Palmitic
acid (16: 0) and stearic acid (18: 0). Palmitic acid is the most widely
occurring SFA, being present in practically every fat examined, it is
present in marine oils, in the milk and depot fats of land animals and in
vegetable fats; main sources include palm oil, cottonseed oil, lard and
beef tallow. Stearic acid is present in most vegetable fats, though a
significant component in only a few, such as cocoa butter and shea
butter. It is also present in most animal fats and is a major component
in the tallow of ruminant fats.
Very-long-chain fatty acids: those with 21 or more carbon atoms e.g.
Behenic acid (22: 0) and lignoceric acid (24: 0)
17
Table 2.2: Commonly used Fatty Acid Nomenclature Systems
System Example Explanation
Trivial
nomenclature Palmitoleic acid
Trivial names (or common names) are non-systematic
historical names, which are the most frequent naming
system used in literature. Most common fatty acids have
trivial names in addition to their systematic names.
These names frequently do not follow any pattern, but
they are concise and often unambiguous.
Systematic
nomenclature
(9Z)-octadecenoic
acid
Systematic names (or IUPAC names) derive from the
standard IUPAC Rules for the Nomenclature of Organic
Chemistry (Rigaudy, 1979) published along with a
recommendation published specifically for lipids (The
Nomenclature of Lipids, Recommendations, 1977).
Counting begins from the carboxylic acid end. Double
bonds are labeled with cis-/trans- notation or E-/Z-
notation, where appropriate. This notation is generally
more verbose than common nomenclature, but has the
advantage of being more technically clear and
descriptive.
Δx nomenclature
cis,cis-
Δ9,Δ
12octadecadienoic
acid
In Δx (or delta-x) nomenclature, each double bond is
indicated by Δx, where the double bond is located on
the xth
carbon–carbon bond, counting from the
carboxylic acid end. Each double bond is preceded by
a cis- or trans- prefix, indicating the conformation of the
molecule around the bond. e.g. linoleic acid is
designated "cis-Δ9, cis-Δ
12 octadecadienoic acid". This
nomenclature has the advantage of being less verbose
than systematic nomenclature, but is no more technically
clear or descriptive.
n - x nomenclature n - 3
n−x (n minus x, ω−x or omega-x) nomenclature
provides names for individual compounds and classifies
them by their likely biosynthetic properties in animals. A
double bond is located on the xth
carbon–carbon bond,
counting from the terminal methyl carbon (designated
as n or ω) toward the carbonyl carbon. e.g α-Linolenic
acid is classified as a n−3 or omega-3 fatty acid, and so
it is likely to share a biosynthetic pathway with other
compounds of this type. It is common in nutritional
literature, but IUPAC has deprecated it in favor
of n−x notation in technical documents (Rigaudy, 1979).
Lipid numbers
18:3
18:3, n - 6
18:3, cis,cis,cis-
Δ9,Δ
12,Δ
15
Lipid numbers take the form C:D, where C is the
number of carbon atoms in the fatty acid and D is the
number of double bonds in the fatty acid. This notation
can be ambiguous, as some different fatty acids can have
the same numbers. Consequently, when ambiguity exists
this notation is usually paired with either a Δx or
n−x term (Rigaudy, 1979)
18
Table 2.3: Common saturated fatty acids in food fats and oils
(FAO, 2008)
Trivial name Systematic name
Abbreviation Typical sources
Butyric acid Butanoic acid C4:0 Dairy fat
Caproic acid Hexanoic acid C6:0 Dairy fat
Caprylic acid Octanoic acid C8:0 Dairy fat, coconut and palm
kernel oils
Capric acid Decanoic acid C10:0 Dairy fat, coconut and palm
kernel oils
Lauric acid Dodecanoic acid C12:0 Coconut oil, palm kernel oil
Myristic acid Tetradecanoic
acid C14:0
Dairy fat, coconut oil, palm
kernel oil
Palmitic acid Hexadecanoic
acid C16:0 Most fats and oils
Stearic acid Octadecanoic acid C18:0 Most fats and oils
Arachidic acid Eicosanoic acid C20:0 Peanut oil
Behenic acid Docosanoic acid C22:0 Peanut oil
Lignoceric
acid
Tetracosanoic
acid C24:0 Peanut oil
Unsaturated Fatty Acids contain one or more double bonds (carbon-to-
carbon)and are found mostly in plants and sea food. Because of the
presence of double bonds, unsaturated fatty acids are chemically more
reactive than SFAs and their reactivity increases as the number of double
bonds increases. As per the FAO/WHO Expert Consultation, unsaturated
fatty acids are classified as:
• Short-chain unsaturated fatty acids: fatty acids with ≤ 19 carbon atoms.
• Long-chain unsaturated fatty acids: fatty acids with 20-24 carbon atoms.
• Very-long unsaturated chain fatty acids: fatty acids with ≥ 25 carbon
atoms.
Further, based on the extent of unsaturation, unsaturated fatty acids (UFA) are
categorized MUFAs and PUFAs and based on the placement of hydrogen on the
double bond they are classified as Cis or Trans isomers.
Cis-Monounsaturated Fatty Acids
Fatty acids containing one double bond are called Monounsaturated Fatty
Acids (MUFA). In general, they have an even number of carbon atoms,
19
between C14 to C24, and the double bond is most likely located at the 9th
position (Table 2.4). Oleic acid (cis-9-octadecenoic acid or 9c-18:1) is the
most frequently occurring cis -MUFA and is also the most widely
distributed of all the natural fatty acids. The other cis -MUFAs though
widely distributed in plants and animal tissues, are very often minor
components of the human diets. Palmitoleic acid (9c-16:1) is the most
widely occurring hexadecenoic acid. It is a minor component in most
animal and vegetable oils, but more significant in marine oils (around
10%), and it is a major component in a few seed oils (e.g. macadamia oil).
C22:1 acid (Erucic acid; 13- cis -docosenoic acid or 22:1n–9) occurs
generally in higher amounts in seed oils of Brassicaceae family, reaching a
level of 40-60% in mustard seed oil and high-erucic acid rapeseed oil.
These oils are consumed in some parts of Asia (particularly India) and
Eastern Europe. MUFAs with more than 22 carbon atoms are rare in
human diets, except for 15c-24:1 which is present as a minor component in
many marine oils.
Polyunsaturated Fatty Acids
Fatty acids containing more than one double bond are called
Polyunsaturated Fatty Acids (PUFA). Natural PUFAs with methylene-
interrupted double bonds and with all cis configuration can be divided
into12 different families ranging from double bonds located from the n–1
to n–12 positions countered from the methyl end (Gunstone, 1999). The
most important families, in terms of human health and nutrition include the
n-6 and n-3.All members of the n-6 family of fatty acids contain their first
double bond between the sixth and seventh carbon atoms from the terminal
methyl group, while all members of the n-3 family of fatty acids have their
first double bond between the third and fourth carbon atoms. Linoleic acid
(LA) is the parent fatty acid of the n-6 family, while α linolenic acid
(ALA) is the parent fatty acid of the n-3 family with both containing 18
carbon atoms. Both LA and ALA series are essential fatty acid (EFA) and
20
can be desaturated and elongated in humans to form a series of n-6 (Lin
series) and n-3 (Lan series) PUFA respectively (Table 2.5).
Table 2.4: Some common cis-monounsaturated fatty acids in fats and oils
(FAO, 2008)
Common name Systematic
Name
Delta
Abbreviation Typical sources
Palmitoleic acid cis-9-
hexadecenoic
acid
16:1Δ9c
(9c-16:1)
Marine oils, macadamia
oil, most animal and
vegetable oils.
Oleic acid cis-9-
octadecenoic
acid
18:1Δ9c
(9c-18:1)
All fats and oils, especially
olive oil, canola oil and
high-oleic sunflower and
safflower oil
Cis-vacceni acid
cis-11-
octadecenoic
acid
18:1Δ11c
(11c-18:1) Most vegetable oils
Gadoleic acid cis-9-eicosenoic
acid
20:1Δ9c
(9c-20:1) Marine oils
Eicosenoic acid cis-11-
eicosenoic acid
20:1Δ11c
(11c-20:1) Marine oils
Erucic acid cis-13-
docosenoic acid
22:1Δ13c
(13c-22:1)
Mustard seed oil, high
erucic acid rapeseed oil
Nervonic acid
cis-15-
tetracosenoic
acid
24:1Δ15c
(15c-24:1) Marine oils
Essential Fatty Acids (EFA)
Essential fatty acids (EFA) are those fatty acids, which the human body
cannot synthesize and therefore, they must be supplied through diet.
EFAs are long-chain unsaturated fatty acids derived from α-linolenic
(Omega-3) and linoleic acids (Omega-6). Oleic acids an Omega-9 MUFA
is necessary yet “non-essential” because the body can synthesize a modest
amount of this fatty acid, provided the other essential fatty acids are
present.
21
EFA deficiency is linked with serious health conditions such as heart
attacks, stroke, cancer, insulin resistance, obesity, diabetes, arthritis,
asthma, lupus, schizophrenia, depression/ postpartum depression,
accelerated aging, attention deficit hyperactivity disorder (ADHD) and
alzheimer’s disease among others (Simpoulos, 1999).Arachidonic acid
(AA) is the most important n-6 PUFA because it is the primary precursor
for the n-6 derived eicosanoids (Table 2.5). It is present, though in low
amounts in meat, eggs, fish, algae and other aquatic plants (Wood et al,
2008; Ackman, 2008). Eiocosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA) on the other hand are the most important n-3
fatty acids in human nutrition.
EPA and DHA are components of marine lipids. Highly specialized
membranes such as synaptic terminals, retinal cells and heart myocytes,
contain very high amounts of AA (20:4 n-6) and DHA (22: 6 n-3). These
EFA are components of phospholipids, mainly the structural lipids (in
highly fluid membranes, contractile cells, and muscular cells) and play
functional roles (e.g. receptor functions, ion channels, neurotransmitter
release). While the AA is in turn converted to hormone-like substances
called eicosanoids including prostaglandins (PGs), thromboxanes (TXs),
prostacyclins, and lipoxins; while DHA is converted to docosanoids. The
eicosanoids and docosanoids play important roles in the regulation of
widely diverse physiological functions, including blood pressure, platelet
aggregation, blood clotting, blood lipid profiles, the immune response and
the inflammation response to injury/ infection.
LA occurs in almost all dietary fats and attains major proportions in most
vegetable oils (White, 2009). ALA is primarily present in plants, occurring
in high concentrations in some seeds and nuts and also in some vegetable
oils, although its presence in conventional diets is much lower than that of
LA. Marine fish such as mackerel, salmon, sardine, herring and smelt are
excellent sources of EPA and DHA (Ackman, 2008).
22
Conjugated Linoleic Acid
Small amounts of positional and geometrical isomers of LA, having two
conjugated double bonds, are also present in the human diet, primarily
derived from ruminant fats. Conjugated linoleic acids (CLA) are a family
of at least 28 isomers of linoleic acid found mainly in the meat and dairy
products of ruminant animals.
As the name implies, the double bonds of CLA are said to be conjugated
as there is only one single bond between the two double bonds.
Conjugated linoleic acid can occur both in a cis and a trans configuration.
The cis bond causes a lower melting point and ostensibly also the observed
beneficial health effects. Unlike other trans fatty acids, the trans CLA may
have beneficial effects on human health. CLA are produced by
microorganisms in the rumen of ruminants as a result of biohydrogenation
of dietary LA. Non-ruminants, including humans, produce certain isomers
of CLA from trans isomers of oleic acid, such as vaccenic acid, which is
converted to CLA by delta-9-desaturase (Kuhnt et al, 2006). More recent
studies using individual isomers indicate that the two isomers c9,t11-CLA
and t10,c12-CLAhave very different health effects (Tricon et al, 2004).
The CLA levels in dairy fats usually range from 0.3–0.6% of total fat
(Parodi, 2003). The beneficial functions of CLA include its antimutagenic,
anticarcinogenic and antiobesity properties as well as its effects on
regulating lipid metabolism and immune response. In view of the health
benefits of trans isomers, in the United States, trans linkages in a
conjugated system are not counted as trans fatty acids for the purposes of
nutritional regulations and labeling.
23
Table 2.5: Nutritionally Important n-3 and n-6 PUFA
(FAO, 2008)
Common name Systematic name N minus
abbreviation Typical sources
Nutritionally important n-3 PUFA
α-linolenic acid cis-9,cis-12, cis-15-
octadecatrienoic
acid
18:3n-3
(ALA)
Flaxseed oil, perilla
oil, canola oil,
soybean oil
Stearidonic acid
cis-6,cis-9,cis-
12,cis-15-
octadecatetraenoic
acid
18:4n-3
(SDA)
Fish oils, genetically
enhanced soybean oil,
blackcurrant seed oil,
hemp oil
Eicosatetraenoic
acid
cis-8,cis-11,cis-
14,cis-17-
eicosatetraenoic
acid
20:4n-3 Very minor
component in animal
tissues
Eicosapentaenoic
acid
cis-5, cis-8,cis-
11,cis-14,cis-17-
eicosapentaenoic
acid
20:5n-3
(EPA)
Fish, especially oily
fish (salmon, herring,
anchovy, smelt and
mackerel)
Docosapentaenoic
acid
cis-7,cis-10,cis-
13,cis-16, cis-19-
docosapentaenoic
acid
22:5n-3 (DPA)
Fish, especially oily
fish (salmon, herring,
anchovy, smelt and
mackerel)
Docosahexaenoic
acid
cis-4,cis-7,cis-
10,cis-13,cis-16,cis-
19-docosahexaenoic
acid
22:6n-3
(DHA)
Fish, especially oily
fish (salmon, herring,
anchovy, smelt and
mackerel)
Nutritionally important n-6 PUFA
Linoleic acid cis-9,cis-12-
octadecadienoic 18:2n-6 (LA) most vegetable oils
γ-linolenic acid cis-6, cis-9,cis-12-
octadecatrienoic
acid
18:3n-6
(GLA)
Evening primrose,
borage and
blackcurrant seed oils
Dihomo-γ-
linolenic acid cis-8,cis-11,cis-14-
eicosatrienoic acid 20:3n-6
(DHGLA)
Very minor
component in animal
tissues
Arachidonic acid
cis-5,cis-8,cis-
11,cis-14-
eicosatetraenoic
acid
20:4n-6 (AA) Animal fats, liver, egg
lipids, fish
Docosatetraenoic
acid
cis-7,cis-10,cis-
13,cis-16-
docosatetrtaenoic
acid
22:4n-6 Very minor
component in animal
tissues
Docosapentaenoic
acid
cis-4,cis-7,cis-
10,cis-13,cis-16-
docosapentaenoic
acid
22:5n-6 Very minor
component in animal
tissues
24
2.2 TRANS FATTY ACIDS AND THEIR FORMATION
The double bonds of most naturally occurring unsaturated fatty acids in food fats
are in the cis configuration, however, double bonds in the trans configuration do
occur in nature. In chemical terms, trans fatty acid refers to a lipid molecule that
contains one or more double bonds in trans geometric configuration. In trans
configuration, the carbon chain extends from opposite sides of the double bond,
rendering a straighter molecule, whereas, in cis configuration, the carbon chain
extends from the same side of the double bond, rendering a bent molecule (Figure
2.2).
Small amounts (2-6%) of trans fatty acids are naturally present in ruminant
deposits and milk fats (Huth, 2007). Trans fatty acids arise in the stomach of
ruminants as a result of the hydrogenation of dietary unsaturated fatty acids during
bacterial fermentation. Human diets contain not only natural trans fatty acids, but
also those arising from technological treatments, such as partial hydrogenation of
Trans Fatty Acids (TFAs) are unsaturated fatty acids that contain at least one
non-conjugated double bond in the trans configuration, i.e. the hydrogen on the
doubly bonded carbon atoms is in the trans configuration, resulting in a straighter
shape (Mozaffarian et al, 2006).
In the Codex Alimentarius, trans fat to be labeled as such is defined as “the
geometrical isomers of monounsaturated and polyunsaturated fatty acids having
non-conjugated [i.e. interrupted by at least one methylene group (-CH2-CH2-)]
carbon-carbon double bonds in the trans configuration”. This definition excludes
specifically the healthy 'trans fats' (vaccenic acid and conjugated linoleic acid)
which are present especially in human milk, dairy products, and beef (FAO/WHO,
2007).Trans fatty acids can be defined as the sum of all isomeric fatty acids with
14, 16, 18, 20 and 22 carbon atoms and one or more trans double bonds, i.e.
C14:1, C16:1, C18:1, C18:2, C18:3, C20:1, C20:2, C22:1, C22:2 trans isomeric
fatty acids.
TFA are less fluid and have a higher melting point than the corresponding cis fatty
acids and include both monounsaturated and Polyunsaturated trans fatty acids,
having either all unsaturations in the trans form or some in trans and other in cis
form (Martin et al, 2007).
25
oils to produce fat blends for margarine, shortening and deep fat frying (Craig-
Schmidt and Teodorescu, 2008).
Partially hydrogenated vegetable and marine oils constitute the main source of
trans fatty acids in human diets in some parts of the world. Trans fatty acids
derived from partial hydrogenation are often referred to as industrial trans fatty
acids (I-TFA). Trans fatty acids are also formed inadvertently during the refining
process of vegetable oils (Ackman et al, 1974). As a result, refined vegetable oils
can contain small amounts (~2%) of trans fatty acids (Ratnayake and Zehaluk,
2005). Both, bio-hydrogenation and industrial partial hydrogenation result in
isomerization of naturally occurring cis unsaturated fatty acids to trans isomers
as well as positional isomers. Thus, partial hydrogenation results in the formation
of an assortment of new cis and trans isomers of MUFA and PUFA. In ruminant
fats and partially hydrogenated vegetable oils, the trans-octadecenoic acid (trans-
oleic or trans-18:1) isomers are the most important group of trans fatty acids. The
position of the double bond of these dietary trans 18:1 isomers, counted from the
carboxylic carbon, usually varies from ∆4 to ∆ 16. The trans 18:1 isomer
distribution in partially hydrogenated vegetable oils depends on the fatty acid
composition of the starting oil, the extent of hydrogenation and very often the
trans 18:1 isomers form a Gaussian distribution that centers around the ∆ 9 or ∆
10 double bond (Ratnayake, 2004).The trans 18:1 isomer distribution of dairy fats
is distinctly different from that of partially hydrogenated vegetable oils. Vaccenic
acid (11t-18:1) is always the major isomer in ruminant fats (30–60% of total t-
18:1), whereas 9t-18:1 and 10t-18:1 isomers occur in relatively low amounts. In
addition to the trans 18: 1 isomers, partially hydrogenated oils contain several cis-
octadecenoic isomers (cis-18:1), wherein double bond position generally ranges
from 6 to 16 (Ratnayake, 2004; Parodi, 1976; Mendis et al, 2008).
Dietary fats also contain a number of positional and geometrical isomers of LA
and ALA which are frequently present in low concentrations in both partially
hydrogenated and non-hydrogenated dietary fats (Ratnayake, 2004). Partially
hydrogenated vegetable oils contain 15 or more isomers of LAs; the major ones
26
being 9c, 12t-18:2 and 9t, 12c-18:2. These isomers are often detected in large
quantities in mildly hydrogenated vegetable oils (up to 6% of total fatty acids),
whereas they are hardly detectable in heavily hydrogenated oils. The LA and ALA
isomers present in non-hydrogenated fats or in many common food fats are the
result of exposure of these PUFAs to some form of heat treatment, such as steam
deodorization or stripping during refining of oils or simple heating in deep fat
frying (Grandgirard, 1994; Ackman et al, 1974). In these processes, the double
bonds do not shift in position, but are isomerized from cis to trans, resulting in the
formation of small amounts of geometric trans isomers of LA and ALA.
2.2.1 History of Trans Fatty Acid
The history of trans fatty acids, dates back to 19th
century. Trans fatty acid
containing partially hydrogenated fat, became popular with consumers and food
manufacturers because it acted as a preservative, giving foods a longer shelf life
(Katan, 2008). It also gave foods a more tempting taste and texture. The
hydrogenation process was first discovered around the turn of the 20th
century,
making it possible to produce partially hydrogenated fat. It was the first man-
made fat to join the food supply.
The synthesis of hydrogenated compounds originated in the 1890s, when French
chemist Paul Sabatier discovered that metal catalysts could be used to precipitate
hydrogenation reactions (for the discoveries concerning catalysts, Paul Sabatier,
shared the 1912 Nobel Prize for Chemistry with French chemist Victor Grignard).
In 1901, German chemist Wilhelm Normann experimented with hydrogenation
catalysts and successfully induced hydrogenation of liquid fat, producing
semisolid fat, which came to be known as trans fatty acids (Eckel et al, 2007).
This process, for which Normann received a patent in 1903, was adopted by food
manufacturers. Products containing unsaturated fats were susceptible to rancidity
upon exposure to air, resulting in a short shelf life (Table 2.6). Therefore, a stable
form of unsaturated fat had the potential to significantly extend the shelf life and
value of a variety of foods. Hydrogenation was important particularly in the
production of margarine, which was used in place of butter when the latter was
27
rationed during World War II (Schleifer, 2012). In the following decades, the use
of hydrogenation to stabilize the shelf life of food products grew rapidly. The first
food product developed that contained trans fatty acids was “Crisco” vegetable
shortening, introduced in 1911 by Procter & Gamble Company. By the 1980s,
many food manufacturers in the western countries had stopped using tallow and
lard, replacing these fats with trans-fat based products, which had similar smoke
points and were thought to be healthier. In India, the partially hydrogenation of
vegetable oil (PHVO) was introduced in 1960s and marketed under the brand
name “vanaspati” (Ghafoorunissa, 2008).
Table 2.6: Landmarks in the History of Trans fatty Acids
Year Developments
1890s French chemist Paul Sabatier developed the hydrogenation process. He
became a Nobel laureate in 1912.
1902 German chemist, scientist, Wilhelm Normann established that liquid oils
can be hydrogenated to form semi-solid fats (trans fatty acids) and got
the process patented. Trans fat became the first man-made fat to join the
food supply.
1911 Procter & Gamble introduced Crisco vegetable shortening in grocery
stores. Crisco became the first food product containing trans fatty acids.
1937 During the second World War, the use of margarine escalated due to the
rationing of butter.
1957 The American Heart Association for the first time proposed that
reducing dietary fats, namely saturated fats found in foods like butter
and beef, can reduce the chances of getting heart diseases.
1960 In India, the partially hydrogenation of vegetable oil (PHVO) was
introduced which was marketed under the brand name “vanaspati”.
1984 Consumer advocacy groups campaigned against using saturated fat
(SFA) for frying in fast-food restaurants. In response, most fast-food
companies began using partially hydrogenated oils containing trans fatty
acids instead of beef tallow and tropical oils high in saturated fats.
1993 Following the release of several scientific studies, health advocacy
groups called for fast-food restaurants to stop using partially
hydrogenated oils in their deep fryers.
1999 The U.S. government proposed a law requiring food manufacturers to
list trans fatty acids amounts on nutrition labels. The proposal was
however, not passed as law.
28
2002 The government agreed with researchers for the first time on record that
there was likely no safe level of trans fat and that people should eat as
little of TFA as possible.
2003 Denmark became the first country to regulate trans fatty acids
consumption on a national basis, putting a very small cap on the amount
of TFA that the food may contain. Later in 2003, the U.S. Food and
Drug Administration (U.S. FDA) passed a law requiring trans fatty acids
to be listed on the Nutrition Facts label on food products; food
manufacturers were given three years to comply. Many reformulated
their products to limit TFA.
2006 Trans fat labeling became mandatory in the United States. The
American Heart Association was the first major health organization to
specify a daily limit: less than 1 percent of calories from trans fatty
acids. Later in the year, New York became the first U.S. city to pass a
regulation limiting trans fatty acids in restaurants. Multiple cities and
states have since proposed similar regulations.
2007 To put trans fatty acids into the context of the overall “big fat picture,”
and help consumers better understand fats and their impact on health,
the American Heart Association launches its “Face the Fats” consumer
education campaign.
January,
2010
Food Safety and Standards Authority of India (FSSAI) organized
“National Consultation on the Proposed Trans Fat Regulation” at NIN
May,
2010
The Food Safety and Standards Authority of India (FSSAI) ask for
comments from stakeholders and the public on the “Revised Draft
Regulation of Trans Fatty Acids (TFAs) in Partially Hydrogenated
Vegetable Oils, PHVOs”. The FSSAI, through the
proposed draft notification, intends to change the limit level of TFA in
PHVO from 10% to 5% within three years. The proposed limit is based
on the recommendations given by National Institute of Nutrition,
Hyderabad.
2010 National Dietary Guidelines Consensus Group formulated the
Consensus dietary guidelines for healthy living and prevention of
obesity, the metabolic syndrome, diabetes, and related disorders in
Asian Indians and recommended that TFAs should be <1% of total
energy/day. (Misra et al, 2011)
2010 The Expert Group of the Indian Council of Medical Research released
the Nutrient requirements and recommended dietary allowances for
Indians, with recommendation in line with FAO/ WHO that TFAs
should be <1% of total energy/day. (ICMR, 2010)
2011 In the revised draft recommended dietary allowances by NIN/ ICMR in
2011, it was recommended that the intake of trans fatty acids should not
exceed 2% of energy (NIN/ ICMR, 2011)
29
Later during the 1990s numerous research studies were conducted, revealing
correlation between the trans fatty acids intake and increased LDL (bad)
cholesterol levels and a higher incidence of heart diseases. Around this time
nutrition labels became a hotly debated topic. Scientists and food manufacturers
argued over whether it is required to separately list the trans fatty acid content on
food packages (Katan, 2008). Table 2.6 briefly summarizes the landmarks in the
history of Trans fatty acids.
2.2.2 Biochemistry of Trans Fatty Acids
TFA are formed in large amounts during artificial processing of vegetable oils
while some amount of TFA exists naturally in dairy products and meats.
Depending on the position of the double bond, several positional isomers are
possible. During partial hydrogenation of vegetable oils, the cis double bonds
present in the fatty acids are converted into trans configuration. This change in
configuration completely alters the physical property of the vegetable oils. The cis
configuration induces a characteristic “U” shaped bend in the acyl chain and
therefore they are less tightly packed and exist as liquid at room temperature due
to lower melting point. Compared to cis, trans configuration has more rigid
structure similar to saturated fatty acids and are tightly packed. Therefore, the
fatty acids in trans configuration exist as solid at room temperature due to high
melting point. Thus, TFA are less fluid and have a higher melting point than the
corresponding cis fatty acids. These class include monounsaturated trans fatty
acids (MTFA), and Polyunsaturated trans fatty acids (PTFA), having either all
unsaturations in the trans form or some in trans form and other in cis form (Wolff,
1992).
2.2.3 Formation and Types of Trans Fatty Acids
Among the processes resulting in TFA formation, hydrogenation of vegetable oils
stands out for its impact on the diet of populations in industrialized countries.
Other processes such as thermal treatments including edible oil refining, meat
irradiation, frying, and bio-hydrogenation also contribute to the dietary intake of
TFA (Martin et al, 2007). Trans fatty acids present in our diet can be naturally
30
occurring/ Ruminant Trans Fatty Acids (N-TFAs) and/ or industrially produced
Trans Fatty Acids (I-TFAs) which are produced during partial hydrogenation and
thermal treatments of oils.
Figure 2.2: Structure of Trans, Cis and Saturated fatty acids
(Source: http://en.wikipedia.org/wiki/Trans_fat)
2.2.3.1 Natural/ Ruminant Trans Fatty Acids: Some TFAs are found naturally
in small amount in ruminant animals and their products like various meat and
dairy products. In animals belonging to the Ruminantia suborder, the action of
microorganisms present in the rumen (Butyrivibrio fibrisolvens and Megasphaera
elsdenii) leads to isomerization of polyunsaturated fatty acids, resulting in
formation of conjugated linolenic acid (18:2 9c, 11t ) and vaccenic acid (18:2 10t,
12c) (Bauman et al, 1999). The effects observed for acids 18:2 9c, 11t and that of
18:2 10t, 12c are distinct from those of the other TFA. Isomer 9c, 11t seems to
have physiological importance as an antioxidant and in the inhibition of several
forms of neoplasias as demonstrated in animal studies (Martin et al, 2007). On the
other hand, the observed effect of the isomer 18:2 10t, 12c on the metabolism of
lipids is important, as this trans fatty acid is capable of generating favorable body
composition changes in some people.
Cis Configuration Trans Configuration Saturated fatty acid
Oleic acid is a cis unsaturated
fatty acid that comprises 55–
80% of olive oil (Alonso et al,
1999).
Elaidic acid is the
principaltransunsaturated fatty acid
found in partially hydrogenated
vegetable oils (Thomas, 2002).
Stearic acid is a saturated fatty
acid found in animal fats
(Thomas, 2002).
Melting Point: 13.4oC Melting Point: 45
oC Melting Point: 66.9
oC
31
Table 2.7: Trans Fatty Acids: Major Isomers with their Sources
(Bhardwaj et al, 2011a)
Trans Fatty
Acid
Process % of
Trans
Fatty
Acid
Major Isomer Sources
Natural/
Ruminant
Trans Fatty
Acid
Bio-
hydrogenatio
n
3-8%
18:1 Δ11t
(Vaccenic acid)
Conjugated
linolenic acid
(CLA; 0.5 -
2%)
Milk, Meat,
Dairy Products
Industrially
produced
Trans Fatty
Acid
Partial
Hydrogenatio
n of
Vegetable
Oils
10 - 50
%
18:1 t (Elaidic
acid, 18:1Δ9t)
(80-95%)
Others
include18:2,
18:3 & 16:1
trans isomers
Vanaspati,
Margarine
Thermal
Treatments
(Deodorizatio
n, cooking &
frying)
1-3 % 18:2 & 18:3
trans isomers
Refined
Vegetable oil,
fried food items
prepared in re-
heated/ re-used
oil
The trans fatty acid content of ruminant products can be changed to some degree
by altering the animals’ feed, although levels of trans fat in milk and meats are
already relatively low ranging from 1 to 8 percent of total fats (Lock and
Bauman, 2004). In fact, most efforts have focused on increasing, rather than
decreasing, the levels of conjugated linolenic acid in ruminant products, owing to
its hypothesized health benefits for humans. However, the evidence of such
benefits is inconclusive. For example, dietary trials indicate that consumption of
conjugated linolenic acid (CLA) reduces insulin sensitivity, increases lipid
peroxidation, and has mixed effects on markers of inflammation and immune
function (Riserus et al, 2004). Of four prospective studies evaluating the relation
between the intake of trans fatty acids from ruminants and the risk of CHD, none
identified a significant positive association, whereas three identified non-
significant trends toward an inverse association (Jakobsen et al, 2008; Oomen et
al, 2001). Another review on the quantitative comparison of the effect of
32
ruminant trans fatty acids and CLA with that of industrial trans fatty acids on
blood lipoproteins in humans indicated that all three classes of trans fatty acids
raise the ratio of LDL to HDL, and therefore, presumably, the risk of coronary
heart disease (Figure 2.3, 2.4. 2.5). The effect of ruminant trans fatty acids and
CLA on the LDL to HDL ratio was less than that of industrial trans fatty acids
although the difference was not significant. However, more studies are needed to
decide whether this difference is real or due to chance (Brouwer et al, 2010). The
absence of concrete evidence of a higher risk of CHD associated with the intake
of trans fatty acids from ruminants as compared to the industrially produced TFA
may be due to lower levels of ruminant TFA intake (typically less than 0.5
percent of total energy intake), different biological effects (ruminant and
industrial trans fatty acids share some, but not all, isomers), or the presence of
other factors in dairy and meat products that balance any effects of the small
amount of TFA, if any.
33
Figure 2.3 Results of randomized studies of the effects of diets high in
industrial trans fatty acids, ruminant trans fatty acids and CLA compared
with cis-unsaturated fatty acids on the ratio of LDL- to HDL-cholesterol.
Source: Brouwer et al, 2010
2.2.3.2 Industrially Produced Trans Fatty Acids (I-TFAs) result from the
industrial processes such as hydrogenation of vegetable oils and thermal
treatments such as refining of vegetable oils, frying of foods and food irradiation.
Figure 2.4Results of randomized studies of
the effects of diets high in industrial trans
fatty acids, ruminant trans fatty acids, CLA
compared with cis-unsaturated fatty acids on
LDL cholesterol.
Figure 2.5 Results of randomized studies of
the effects of diets high in industrial trans
fatty acids, ruminant trans fatty acids, CLA
compared with cis-unsaturated fatty acids
on HDL cholesterol.
34
Hydrogenation of Vegetable Oils: TFAs are mainly produced when the oil
is converted to solid fat through a chemical process – hydrogenation,
wherein hydrogen is added to unsaturated fatty acids in vegetable oil(s).
This changes the fat from a liquid to a soft/solid state simultaneously
generating TFAs (Mozaffarian et al, 2006). The TFA content of the
hydrogenated fat varies from 10-40%. Several factors such as
polyunsaturated fatty acid (PUFA) composition of the native oil, type of
catalyst used and the hydrogenation conditions such as temperature and
pressure determine the trans fatty acid level and the type of trans isomer.
The major trans isomer present in the partially hydrogenated vegetable oil
is 18:1t (80-90%) isomer. Among the 18:1t isomer, elaidic acid (18:1 ∆9 t)
is the major trans isomer (85- 90%). Other trans isomers include 16:1t,
18:2t and 18:3t.
Partially hydrogenated vegetable oils can replace naturally solid, saturate-
rich fats (such as Desi Ghee, butter, lard etc.) in baked/fried foods, Indian
sweets as well as in commercial frying where vegetable oils cannot be
used. These fats are preferred by commercial food processors as they
accord a longer shelf life and impart desirable taste, shape, and texture to
the food; they are also used in baked products or are formed in the foods
while frying. The production of high TFA containing fats was considered
important for many decades by the hydrogenation industry not only to
increase shelf life, but also mainly to improve the physical, chemical, and
organoleptic characteristics of fats (Johnson, 1998).
Thermal Treatments: The thermal processes causing the formation of
trans fatty acids include refining of vegetable oils, frying of food and food
irradiation.
Refining of Vegetable Oils: Due to the exposure to high temperature,
small amount of TFA are also reportedly formed during the refining of
vegetable oils. Edible oils are subjected to refining in order to remove
certain impurities/ naturally present attributes (free fatty acids,
phospholipids, carbohydrates, and proteins as well as their degradation by-
35
products; water, chlorophyll, carotenoids, and fatty acid oxidation
products) which may alter the color, taste, and aroma. Such substances can
often restrict the application of oil, and reduce their shelf life. Refining
generally includes degumming, neutralization, bleaching, and
deodorization.
During refining, the vegetable oils are commonly heated between 60◦C and
100◦C; and then subjected to deodorization, which aims to improve oil’s
organoleptic characteristics by removing oil solvents used during the
process of extraction as well as low molecular weight compounds naturally
present in the oil. During deodorization process, the temperature is raised
(180 to 270ºC) which leads to formation of TFA in the vegetable oil
(Bhardwaj et al, 2011a). Double bonds in the fatty acids of vegetable oils
subjected to the high temperatures during refining, especially the
deodorization process, undergo geometrical isomerization from the cis to
trans configuration. Oleic acid is hardly affected, while α-linolenic acid
has a greater tendency to isomerization even than linoleic acid. The two
possible mono-trans isomers of linoleic acid (i.e. 9c, 12t-18:2 and 9t, 12c-
18:2) are formed in roughly equal amounts, while the all-trans isomer (9t,
12t-18:2) is produced at a much lower concentration (Moreno et al, 1999).
Frying of Food: Frying is one of the oldest and popular methods of food
preparations. Fried foods have a characteristic flavour, colour, and crispy
texture, which make deep-fat fried foods very popular among the
consumers. Frying is the process of immersing food in hot oil allowing a
close contact between air and food at high temperatures of nearly 150ºC to
190ºC or more. The simultaneous heat and mass transfer of oil, food and
air during deep-fat frying produces the desirable and unique quality of
fried foods; the frying oil acts as a heat transfer medium and contributes to
the texture and flavour of the fried food. During deep fat frying, edible
oils/fats undergo various chemical reactions which include oxidation,
hydrolysis, isomerization, polymerization and cyclization. As a result, a
36
multitude of products like free fatty acids, trans fatty acids, mono and
diacylglycerols, oxidized monomers, dimers and polymers are formed. At
the high temperatures of frying, thermal reactions occur, giving rise to
cyclic monomers, dimers and polymers (Goyal and Sundararaj, 2009). As
a result of these reactions several physical and chemical changes also
occur in the oil, producing numberless substances that are incorporated
into foods and which alter their appearance, aroma, and taste (Moreno et
al, 1999). Foods fried in deteriorated oil/fat absorb these products, many of
which are potentially toxic on consumption.
During food frying, formation of TFA is closely related to the processing
temperature and the oil use time (Moreno et al, 1999). Double bonds in the
fatty acids of vegetable oils subjected to the high temperatures during
frying, can also undergo geometrical isomerization from the cis to trans
configuration. Further, when instead of oils partially hydrogenated fats are
used, due to their comparatively lesser unsaturation the formation of TFA
is generally lower; however, their initially high TFA content results in a
larger concentration of trans isomers in the fried food. Several European
countries have specified that the frying oil temperature must not exceed
180◦C. In France, it has been established that the oil commercially used in
frying must contain at the most 3% alpha-linolenic acid (Wolff, 2002).
These measures not only help to decreased degradation of unsaturated fatty
acids but also result in a lower level of mono or poly trans fatty acids
(MTFA and PTFA) formation.
Food Irradiation: It is a form of food processing to extend the shelf life
and reduce the spoilage of the food (Minami et al, 2012). The use of
irradiation technology in food preservation has raised interest mainly due
to its efficiency and its multiple possible applications. Irradiation of meat
increases its shelf life by protecting it from pathogenic microorganisms;
however, it also produces structural changes in many nutrients, which may
have adverse consequences on nutritional value of foods. The free radicals
formed by irradiation of unsaturated fatty acids react with them leading to
37
the formation of carbonyl compounds, which are responsible for associated
changes in the nutritional and organoleptic characteristics of food (Martin
et al, 2007). Furthermore, breaking of the double bonds favours the
formation of TFA as its conversion in the trans configuration reduces the
free energy of the fatty acid. Minami et al (2012) examined the effects of γ
irradiation on the fatty acid composition, lipid peroxidation level, and
antioxidative activity of soybean and soybean oil. The results indicated
that irradiation at 10 to 80 kGy under aerobic conditions did not markedly
change the fatty acid composition of soybean, while 10-kGy irradiation did
not markedly affect the fatty acid composition of soybean oil under either
aerobic or anaerobic conditions. However, 40-kGy irradiation considerably
altered the fatty acid composition of soybean oil under aerobic conditions.
Further, 40-kGy irradiation produced a significant amount of trans fatty
acids under aerobic conditions. Irradiating soybean oil induced lipid
peroxidation and reduced the radical scavenging activity under aerobic
conditions, but had no effect under anaerobic conditions. These results
indicate that the fatty acid composition of soybean was not markedly
affected by radiation at 10 kGy, and that anaerobic conditions reduced the
degradation of soybean oil that occurred with high doses of γ radiation.
There are many controversies on appropriate doses for food irradiation.
Countries such as the United States and Canada have established that for
the red meat group, irradiation of fresh food must not exceed 4.5 kGy
(Kilogrey) while in England up to 7.0 kGy, and in South Africa upto 45
kGy is permitted (FDR, 2002).
2.2.4 Dietary Sources of Trans Fatty Acids
In developed countries some quality data on TFA content of various food items
do exist (Table 2.8). However, in India not much work has been done regarding
laboratory analysis of TFA content of commonly consumed food articles.
Therefore, Misra et al, (2009a) have reported TFA content of certain commonly
consumed food articles (Table 2.9) based on the levels of TFA content from
studies by Ghafoorunisa and Krishnaswamy (1994).
38
Table 2.8: Dietary Sources of TFA
S.No Source of TFA Category of Foods Food Items with their
TFA content (g/100 gm)
I
TFA formed during partial
hydrogenation of vegetable
oils e.g. vanaspati,
margarines
(i) Baked foods Cakes*(2.7), Cookies*(5.9),
Muffin*(1.3), Brownie*(3.4),
Pizza*(0.5)
(ii) Foods fried/cooked
in partially
hydrogenated
vegetable oil
French fries*(4.2-5.8)
II
TFA found naturally in
milk, milk products and
body fat of ruminant
animals (e.g. cattle,
buffalo, goats, etc)
Naturally occurring
foods
Milk**, dairy products**,
Meat from ruminant
animals** (mutton, beef etc.)
* Mozaffarain et al, 2006. **Exact TFA content among these food items is not known; and requires further investigation
Table 2.9: Fatty Acid Content of Some of the Cooked Food Items Frequently
Consumed in India (g/typical serving)
(Misra et al, 2009a)
# Fatty acids have been calculated on thebasis of fatty acid content of raw ingredients present in
food articles (Ghafoorunissa and Krishnaswamy, 1994; Gopalan et al, 1989) however TFA
content as per the laboratory analysis may differ.† Values for trans fatty acid content are given for
a typical serving. ‡Prepared in a combination of Vanaspati (hydrogenated fat) as shortening and
refined vegetable oil as the frying medium. §Prepared in Vanaspati. * Prepared in refined
sunflower seeds oil.
Nutrients† Parantha‡ Bhatura‡ Pulao§ Pakora* Dosa* Samosa‡ Fried
potato
chaat§
Halwa§
Typical
serving
size (g)
80 60 275 100 90 70 100 100
Total fat
(g)
12.03 20.32 11.61 17.40 11.36 15.64 15.6 20.73
SFA (g) 2.01 2.52 2.76 1.65 1.23 2.28 3.75 4.91
MUFA (g) 2.42 4.58 2.22 4.21 2.77 3.60 3.00 3.90
PUFA (g) 4.38 11.04 0.76 11.11 7.12 7.12 0.65 0.81
n-3 PUFA
(g)
0.15 12.16 0.06 0.09 0.22 0.09 0.12 0.33
n-6 PUFA
(g)
4.23 10.90 0.70 11.07 6.90 7.03 0.53 0.73
TFA (g) 2.72 4.45 5.30 0.21 0.142 2.79 7.95 10.6
39
2. 3 METABOLISM OF TRANS FATTY ACIDS
Although there is a clear understanding about the digestion, absorption and
metabolism of fats and fatty acids (as given in box and figure 2.5), there is scanty
literature available on the exact metabolism of trans fatty acid. The exact
biochemical methods by which trans fatty acids produce specific health problems
are a topic of continuing research. One theory is that the human lipase enzyme
works only on the cis configuration and cannot metabolize a trans fatty acids. A
lipase is a water-soluble enzyme that helps digest, transport, and process dietary
lipids such as triglycerides, fats, and oils in most of the living organisms. The
human lipase enzyme is ineffective against the trans configuration, so trans fatty
acid remains in the blood stream for a much longer period of time and is more
prone to arterial deposition and subsequent plaque formation.While the
mechanisms through which trans fatty acids contribute to coronary heart disease
are fairly well understood, the mechanism for trans fatty acids effect in diabetes is
still under investigation (Aro et al, 1997).
Figure 2.6: Digestion and Absorption of Fats in Human Body
(Source; Mahan and Escott-Stump, 2008)
40
Digestion, Absorption and Metabolism of Fats: Lipid metabolism is closely connected to the
metabolism of carbohydrates which may be converted to fats. Fatty acids are usually ingested as
triglycerides (triacylglycerols), but being water insoluble they cannot be absorbed by the intestine.
Therefore, they are first emulsified in the small intestine by bile salts forming micelles. Micelles
also serve as transport vehicles for those lipids that are less water-soluble than fatty acids, such as
cholesterol or fat-soluble vitamins A, D, E, and K.
Digestion of Fats: The emulsification of fats renders them susceptible to hydrolysis by pancreatic
lipase; which is virtually specific for the hydrolysis of primary ester linkages, the 1 or the 3 ester
bonds. As a result of this conversion 2-monoglyceride (2-monoacylglycerols) is formed.
Absorption of Fats: Short-chain fatty acids (up to 12 carbons) are absorbed directly through the
villi of the intestinal mucosa, enter the blood via capillaries that empty into the portal vein and are
transported via lipid carrier proteins directly to the liver, where they are used for energy
production. 2-Monoglycerides, long-chain fatty acids (more than 12 carbons), cholesterol and
lysophospholipids are absorbed from the lumen by intestinal mucosal cells, where they are
incorporated into lipoproteins and directed to the lymphatic system. Once across the intestinal
barrier, the triglycerides are re-synthesized. The triglycerides and other lipids (phospholipids and
cholesterol) appear in the form of chylomicrons that passes through the lymphatic vessels of the
abdominal region and later to the systemic blood. In the capillaries the extracellular enzyme
lipoprotein lipase (activated by apo C-II) hydrolyses triacylglycerols to fatty acids and glycerol
which are taken up by the cells in the targeted tissue. In muscle, the fatty acids are oxidized for
energy and in adipose tissue they are re-esterified for storage as triacylglycerols (stored as fat in
adipose tissue). The remnants of chylomicrons, depleted of most of their triacylglycerols but still
containing cholesterol and apolipoproteins, travel in the blood to the liver. In liver they are taken
up by endocytosis and processed into the various lipoprotein forms particularly VLDL-c and LDL-
c. Triacylglycerols that enter the liver by this route may either be oxidized to provide energy or act
as precursors for the synthesis of ketone bodies. In brief Chylomicrons carry diet-derived lipids to body cells, VLDL-c carry lipids synthesized by
the liver to body cells, LDL-c carry cholesterol around the body, HDL-c carry cholesterol from the
body back to the liver for breakdown and excretion (Figure 2.6).
Metabolism of Fats: The main pathways of lipid metabolism are lipolysis, beta-oxidation,
ketosis, and lipogenesis. Lipolysis is the breakdown of lipids, which involves the hydrolysis of triglycerides into free fatty
acids. β-oxidation is a cyclical process by which fatty acids, in the form of Acyl-CoA molecules, are
broken down in mitochondria and/or in peroxisomes to generate Acetyl-CoA, the entry molecule
for the Citric Acid cycle. In this process two carbons are removed from the fatty acid per cycle in
the form of acetyl CoA, which proceeds through the Krebs cycle to produce ATPs, CO2, and
water. Ketosis is a metabolic state that occurs when the liver converts fat into fatty acids and ketone
bodies, which can be used by the body for energy. It occurs during prolonged starvation and when
large amounts of fat are eaten in the absence of carbohydrate i.e. when the rate of formation of
ketones by the liver is greater than the ability of tissues to oxidize them. Lipogenesis is a process by which acetyl-CoA is converted to fats. It occurs in the cytosol. The
fatty acids are derived from the hydrolysis of fats, as well as from the synthesis of acetyl CoA
through the oxidation of fats, glucose and some amino acids. Lipogenesis from acetyl CoA also
occurs in steps of two carbon atoms. NADPH produced during the pentose-phosphate shunt is
required for this process. Phospholipids generated from triglycerides (TG) form the interior and exterior cell membranes
and are essential for cell regulatory signals (FAO/ WHO, 2003; Mahan and Escott-Stump, 2008).
41
2.3.1 Metabolism and Mechanism of Action of Trans fatty Acids
In general, nearly all isomeric cis and trans fatty acids (both ruminant and
industrial), when fed as part of a mixed diet, are efficiently absorbed and
incorporated into chylomicrons with the possible exceptions of fatty acids with
double bonds in the Δ2 to Δ7 positions.
Once the chylomicrons reach the liver, the fatty acids are repackaged into
triacylglycerols and exported into the circulation in the form of VLDL-c and
LDL-c (with little or no discrimination between cis and trans isomers in
triacylglycerol synthesis). Thereafter they are transported to the peripheral tissues,
where they are hydrolysed and taken up by the cells. In animal studies the
hydrolysis of cholesterol esters containing trans fatty acids was significantly lower
than those with cis double bonds highlighting that there is specificity in the
manner in which TFA are utilized by acyltransferases (Kinsella et al, 1981).
In human plasma, fatty acids in position 2 of phosphatidylcholine are transferred
to cholesterol to form cholesterol esters by the enzyme lecithin cholesterol acyl
transferase which strongly discriminates against the incorporation of trans isomers
of linolenic acid. In vivo, trans fatty acids are preferentially esterified into the Sn-l
position of phospholipids although trans-cis isomers of unsaturated fatty acids
may be acylated into Sn-2 position, particularly when saturated fatty acids occupy
position Sn-l. To quote an example di-trans 18:2 is incorporated preferentially into
position 1 of phosphatidylcholine and into the Sn-1 and Sn-3 positions of the
triacylglycerols, like the saturated fatty acids. In contrast, trans-cis fatty acids (9c,
12t-18:2) like linoleic acid (di-cis fatty acid) is incorporated into the Sn-2
position. It therefore, appears that the trans-15 ethylenic bond may be perceived as
a single bond by the acyltransferases involved. Support for this hypothesis comes
from a finding that esterification of 9c,12t-18:2 into position 2 of
phosphatidylcholine was similar to that of 9c-18:1.Once the plasma lipids reach
other tissues, both cis and trans fatty acids are rapidly taken up and incorporated
into tissue lipids. However, trans PUFA (9c, 12c, 15t-18:3) is selectively
incorporated into cardiolipin (phospholipid occurring primarily in mitochondrial
42
inner membranes) in a very similar manner to linoleic acid which is its structural
analogue.
The amounts of trans fatty acids absorbed and incorporated into tissue lipids
depends on their concentration in the diet. The deposition of trans fatty acids in
tissues may be selective. Thus adipose tissue and liver generally contain higher
levels of TFA than other tissues (Table 2.10) while, minimum deposition of trans
18:1 occurs in the brain (Schrock and Connor, 1975). After cessation of feeding,
depletion of trans 18:1 from the tissues occurs at a rate equivalent to that observed
for saturated fatty acids, normally taking about 4 to 8 week on the other hand
several studies have reported that trans fatty acids are oxidized at rates equivalent
to the corresponding cis isomers (Alfin-Slater and Aftergood, 1979; Kinsella et al,
1981). One study reported that animals consuming a diet containing trans
octadecenoate for a prolonged period might accumulate the trans fatty acids in
their depot fat, while in another study it was reported that trans 18:2 was rapidly
catabolized in rat liver, whereas cis 18:2 was elongated and acylated into
glycerolipids. Complete oxidation of trans isomers may not occur in all instances
and shortened isomers, i.e., trans 16: 1 and trans 14: 1 may accumulate (Wood,
1979).
Table 2.10: Trans Fatty Acid Concentration in Human Tissue Samples
Human Tissue Samples Trans Fatty Acid Concentrations (%)
Adipose Tissue * 2.4 to 12.2
Liver Tissue * 4.0 to 14.4
Heart Tissue * 4.9 to 9.3
Aortic Tissue * 2.3 to 8.8
Serum lipid (t18: 1) 1.9
Serum lipid (t18: 2) 0.8
Erythrocytes (t18: 1) 2.4
Erythrocytes (t18: 2) 0.7
* Primarily trans 18:1, but also contains trans 18:2
(adapted from Perkins et al, 1977)
43
Desaturation and Elongation: The incorporation of trans fatty acids into
membrane phospholipids may alter the packing of the phospholipid and
possibly influence the physical properties of the membrane as well as the
activities of the membrane associated enzymes (Kinsella et al, 1981), like
elongase, desaturase and PG synthetase. The trans fatty acids are converted
to CoA esters which act as substrates for acyl transferases and some
desaturases. Certain trans fatty acids are elongated and desaturated, and
possibly may decrease the availability of the natural cis polyunsaturated
fatty acids for prostaglandin (PG) synthesis by displacing them from the
various phospholipid fractions. Certain positional isomers of trans 18:1 can
be desaturated by ∆9 desaturase, and thus may compete with stearic acid
(18:0) which is the normal substrate for this desaturase.
Trans Fatty Acid; Linoleic Acid and Alpha Linolenic Acid: Animal
studies have suggested that di-trans-18:2 inhibits the elongation and
desaturation of linoleic and alpha linolenic acids. Linoleic acid is the
critical essential fatty acid which serves as the dietary precursor of
arachidonic acid (AA; 20:4n-6), while ALA is converted to
eicosapentanoic acid (EPA) which is further converted to docosahexaenoic
acid (DHA) in the body. Arachidonic acid (AA; 20:4n-6) and DHA
(22:6n-3) are critically important in fetal and infant growth as well as the
development of central nervous system (Elias and Innis, 2001).
Arachidonic acid is found in cell membrane phospholipids and cell
signaling pathways in cell division; and is the principal precursor of the
prostaglandin (PG), thromboxane, prostacyclin, and related endoperoxides
(Fig 2.6 and 2.7). There is clinical evidence supporting a relation between
blood lipid AA and infant growth and experimental evidence showing that
dietary AA reverses the growth failure resulting from deficiency of
essential fatty acids (Shoji et al, 2011). DHA on the other hand is involved
in visual and neural functions as well as neurotransmitter metabolism, its
concentrations being high in retinal and brain membrane phospholipids.
44
Liver microsomes have three desaturases which act on carbons 5, 6, and 9
of dietary fatty acids (Elias and Innis, 2001). The ∆6 desaturase which acts
on dietary linoleic acid (18:2 n-6) is a rate controlling enzyme in PUFA
synthesis. The ∆6 and ∆5 desaturases are involved in the conversion of
essential fatty acids to PG precursors [eicosatrienoic acid (20:3n-6)] and
arachidonic acid (20:4n-6); and since trans isomers of mono and dienoic
acids may inhibit these desaturases, they affect PG metabolism and their
diverse functions. It has been suggested that the trans isomers of oleic acid
(18:1) and linoleic acid (LA; 18:2 n-6), have adverse effects on growth and
development by inhibiting the desaturation and elongation of linoleic (LA)
and α-linolenic acid (ALA; 18:3n-3) to AA and DHA, respectively. In a
study, when trans-18:3 isomers were fed to animals in the form of heat-
isomerized linseed oil, they brought about a decrease in the concentration
of arachidonic acid (20:4 n-6) as well as in the ratio of arachidonic acid
(20:4 n-6) to linoleic acid (18:2 n-6) in the phospholipids of liver in
comparison to the animals fed fresh linseed oil. However, there are
conflicting views on this as some studies suggest that this only occurred
when very high levels of trans 18:3 isomers were fed.
Trans Fatty Acid and Essential Fatty Acid: Animal studies suggest that
trans fatty acids in the diet tend to increase the need for essential fatty acid
(EFA). In EFA deficiency, trans fatty acids accentuate dermal symptoms
and suppress growth and even relatively low levels of dietary trans
C18:2n-6 reduced the liver desaturase activity. Dietary trans 18: 1 inhibits
the conversion of linoleic acid (l8:2n-6) to arachidonic acid (20:4n-6) and
that of oleic acid (18:1) to mead acid (20:3n-9) apparently by acting as a
competitive inhibitor for the desaturase enzyme. This may partly explain
the mechanism by which trans monoenes (and trans, trans dienes)
exacerbate EFA deficiency symptoms (Figure 2.6).
Trans Fatty Acid and Lipoproteins: In controlled trials, consumption of
trans fatty acids reduces the activity of serum paraoxonase, (deRoos et al,
45
2002) an enzyme that is closely associated with HDL cholesterol, and
impaired postprandial activity of tissue plasminogen activator. (Muller et
al, 2001). In humans, TFA consumption increases plasma activity of
cholesteryl ester transfer (CET) protein, the main enzyme for the transfer
of cholesterol esters from HDL to LDL and VLDL cholesterol. This
increased activity may explain decreases in the levels of HDL and on the
other hand increases in the of LDL and VLDL cholesterol levels observed
with intake of trans fatty acids. Trans fatty acids also influence fatty acid
metabolism of adipocytes, resulting in reduced triglyceride uptake,
reduced esterification of newly synthesized cholesterol, and increased
production of free fatty acids. Consumption of TFA rich diets increases the
fasting plasma CET protein activity relative to the other major dietary fatty
acids. Although many other factors, such as lipoprotein receptor activity
and rates of lipoprotein secretion, could be involved, studies showing
increased fasting ratios of LDL to HDL cholesterol after short-term
consumption of high TFA diets support the role for TFA in regulating CET
protein activity (Mozaffarian et al, 2006).
In respect of Apo-lipoprotein, trans fatty acids appear to affect lipid
metabolism through several pathways. In vitro, trans fatty acids alter the
secretion, lipid composition, and size of apolipoprotein B-100 (apoB-100)
particles produced by hepatic cells (Mitmesser and Carr, 2005). Diets rich
in TFAs have also been shown to increase plasma concentration of
apolipoprotein a [apo(a)] compared with diets containing similar amounts
of oleic acid, stearic acid, palmitic acid or SFA combinations (Mozaffarian
et al, 2006).
Effects of Trans Fatty Acid on Eicosanoid Production: The eicosanoids
are derived primarily from arachidonic acid by the action of cyclo-
oxygenases and lipoxygenases (Figure 2.7 and 2.8); and they have a wide
range of functions in tissues at low levels, especially in relation to
inflammation. Fatty acids in the diet with trans double bonds could
46
potentially inhibit eicosanoid metabolism by reducing the availability of
substrates or by inhibiting the action of specific enzymes. Certain studies
have shown that Trans-dienoic isomers in hydrogenated fat inhibited
prostacyclin released by endothelial cells in the presence of high level of
linoleic acid e.g. 14-trans-20:4 inhibited the conversion of arachidonic acid
(20:4; n-6) to thromboxanes, and was itself converted into other eicosanoid
metabolites, while 17-trans-20:5 and 19-trans-22:6 inhibited the 12-
lipoxygenase and cyclooxygenase pathways, respectively (Muller et al,
1998; Mozaffarian et al, 2006).
Trans Fatty Acid and Prostaglandin Biosynthesis: Linoleic acid is the
critical EFA that serves as the precursor of prostaglandin (PG),
thromboxanes, prostacyclin, leukotrienes, hydroxy fatty acids, and related
endoperoxides (Mozaffarian et al, 2006). Availability of precursor acids is
one of the important factors regulating the biosynthesis of PGs (Oh et al,
2005). In a study using very high concentrations of dietary trans, trans
linoleate (alone) and in combination with cis, cis 18:2 fatty acids, it was
observed that TFA affected the level of PG precursors in various tissues
and the capacity of blood platelets to synthesize PGs. Animal studies have
also indicated that TFA interfered with the metabolism of essential fatty
acids thereby impairing their conversion to PGs. Abnormally high levels
of dietary trans fatty acids exert a greater impact on PG production than is
apparent from their effects on levels of the respective PG precursor fatty
acids. This may indicate that the trans, trans 18:2 fatty acid or its metabolic
derivatives inhibited some of the enzymes involved in prostaglandin
synthesis. The possible inhibition of PG synthase by trans fatty acids may
further implicate them in the exacerbation of EFA deficiency symptoms.
This may in part explain why the classical clinical symptoms of EFA
deficiency are more severe in the rats receiving high dietary levels of trans,
trans 18:2 (Mozaffarian et al, 2006).
47
Figure 2.7: Essential fatty acid production and metabolism to form
Eicosanoids
(Source: Abramczyk et al, 2011)
48
Figure 2.8: Arachidonic acid cascade, depicting biosynthesis of AA eicosanoid
products.
(Source;http://en.wikipedia.org/wiki/Eicosanoid)
There are several possible mechanisms whereby TFA may affect both lipid and
non-lipid risk factors for cardiovascular disease. The cellular mechanisms relating
trans fatty acids to inflammatory pathways and other, non-lipid pathways are not
well established. Monocytes and macrophages, endothelial cells, and adipocytes
may each play a role. Trans fatty acids modulate monocyte and macrophage
responses in humans, increasing the production by monocytes of TNF-α and
interleukin-6. Trans fatty acids have been shown to increase circulating
biomarkers of endothelial dysfunction and to impair nitric oxide dependent arterial
dilatation. Each of these pathways warrants additional investigation, particularly
the potential influence of trans fatty acids on nuclear receptors, membrane
receptors, and membrane fluidity. (Baer et al, 2004)
49
Dietary TFA have also been seen to adversely affect various hemostatic and
hematobiological properties of blood, enzyme activities and alter the properties of
membrane phospholipids (Clandinin et al, 1991). Mitochondria from rats fed trans
fatty acids are more susceptible to swelling and show lower rates of oxidative
phosphorylation (Mozaffarian et al, 2006). Takatori et al (1976) concluded that
the influence of trans fatty acids appeared to be out of proportion to their
concentration in the diet because even relatively small concentrations
accumulating in the tissues, significant metabolic effects were observed.
2.4 HEALTH HAZARDS ASSOCIATED WITH TFA CONSUMPTION
Since TFA have a similar but straighter chemical structure as compared to the
‘cis’ form of fatty acid, the body therefore, recognizes this chemical structure and
uses it for same purposes as ‘cis’ form, but TFA stacks together just like saturated
fats sabotaging the flexible, porous functionality needed by the body (Mozaffarian
et al, 2006; Ghafoorunissa, 2008; ASCN/ AIN-1996).Trans-fatty acids can compete
with natural fatty acids in enzymatic reactions involved in prostaglandin synthesis
and can thus affect platelet activity and other critical functions. Metabolic studies
have shown various adverse effects associated with high TFA consumption (Table
2.10), which include:
Obesity: Findings from long-term studies suggest that TFA consumption
promotes weight gain, particularly the accumulation of abdominal fat. A
long term study on monkeys showed that high intake of TFAs (8 en %)
significantly increased weight gain with increased intra-abdominal fat
deposition and is also associated with insulin resistance even in the
absence of caloric excess (Kavanagh et al, 2007). Further TFA intake was
associated with hyperphagia, increased fat accumulation in the liver and
visceral adipose tissue as well as impaired glucose tolerance, all of which
are important features of the metabolic syndrome (Thompson et al, 2011).
In the cohort study on 16000 men who provided two measurements of
abdominal circumference over 9 years, each 2 en% increase in TFA
consumption was associated with a 2.7cm increase in abdominal
50
circumference after adjusting for measurement error and other risk factors
(Koh-Banerjee et al, 2003). In another study carried out on more than
41000 women who provided two measurements of weight over 8 years,
increases in TFA consumption were robustly associated with increase in
body weight in both cross-sectional and longitudinal analyses, after
adjustment for other risk factors (Field et al, 2007). In both of these
studies, changes in consumption of other fats, including total fat, SFA,
MUFA and PUFA, were much less strongly associated with
adiposity/weight gain, consistent with prior findings that neither total
dietary fat nor most fat subtypes are major determinants of body fat or
weight gain (Willett and Leibel, 2002).
Cardiovascular Diseases: Consumption of TFAs adversely affects blood
lipids and lipoproteins beyond changes in low density lipoprotein
cholesterol (LDL-c) and high density lipoprotein cholesterol (HDL-c).
TFA consumption raise the very low density lipoprotein (VLDL-c) and
LDL-c levels and lower the HDL-c, causing heart diseases. It also leads to
reduced triglyceride uptake and production of free fatty acids
(Ghafoorunissa, 2008; Bhardwaj et al, 2011a). Compared with MUFA or
PUFA, TFAs also raise the fasting triglyceride levels (Mozaffarian and
Clarke, 2009).
TFA consumption increases the levels of Lp (a) [lipoprotein-a] and
reduces the LDL-c particle size which is a possible independent CHD risk
factor (Mauger et al, 2003; Mozaffarian 2006; Bhardwaj et al, 2011a).
Intake of partially hydrogenated vegetable oils contributes to the risk of
myocardial infarction (Ascherio et al, 1994).There are several other
mechanisms through which TFA may affect both, lipid and non-lipid, risk
factors for cardio vascular diseases. TFA consumption has been found to
be associated with significantly higher levels of soluble TNF-α receptors
(circulating biomarkers of TNF- α system activity) after adjustment for
other risk factors that might influence inflammation (including age,
51
smoking, physical activity, medication, alcohol consumption and other
dietary habits) (Mozaffarian et al, 2004a). It also increases the levels of
inflammatory markers Interleucin-6 (IL-6) and high-sensitivity C reactive
protein (hs-CRP), specifically among obese individuals (Lopez et al,
2005). Studies suggest that TFA consumption increases TNF- α activity,
among individuals with greater adiposity, IL-6 and hs-CRP (Figure 2.9).
Thus, both observational studies and controlled trials indicate that TFA
consumption is proinflammatory, leading to thickening of the arteries
(atherosclerosis), diabetes, and sudden death due to heart failure
(Mozaffarian et al, 2004; Mozaffarian, 2006). Ecologic studies have
suggested that the consumption of TFAs is positively associated with
ischemic heart disease (IHD) risk (Gatto et al, 2003; Karbowska and
Kochan, 2011).
Increased risk of IHD associated with TFA intake involves elevations in
both apolipoprotein (a) [apo (a)] concentrations and the ratio of LDL to
HDL cholesterol. High concentrations of apo (a), LDL cholesterol and low
concentrations of HDL cholesterol in fasting plasma are important
independent predictors of IHD risk (Wild et al, 1997). In randomized
crossover study, targeted to investigate whether postprandial lipoprotein
metabolism is affected by the consumption of trans fatty acids revealed
that consumption of meals high in trans fatty acids results in higher
Cholesteryl ester transfer (CET) protein and postprandial lipoprotein
concentrations enriched with apo (a) than does consumption of meals free
of trans fatty acids (Figure 2.8). TFA consumption is also associated with
higher levels of several circulating markers of endothelial dysfunction,
including soluble intercellular adhesion molecule-1, soluble vascular cell
adhesion molecule-1 and E-selectin (Lopez et al, 2005). Endothelial
dysfunction is a key step in the development of atherosclerosis
(Mozaffarian et al, 2004).
52
Insulin Resistance and Diabetes: Insulin resistance is an important risk
factor for type 2 diabetes. It precedes the development of type 2 diabetes
and as already indicated it is associated with multiple cardiovascular risk
factors (obesity, dyslipidemia, low HDL-c, hypertension, impaired glucose
tolerance further leading to metabolic syndrome). TFA have shown to
increase insulin resistance and seem to have a unique cardio-metabolic
imprint that is linked to insulin-resistance and metabolic-syndrome
pathways (Micha et al, 2009).
Recent studies have shown that insulin resistance is initiated in adipose
tissue which in turn affects insulin sensitivity of skeletal muscle and liver.
Several animal and human studies have investigated the impact of dietary
TFA on glucose-insulin homeostasis. Animal studies have demonstrated
that both SFA and TFA decrease insulin sensitivity as is evident by
increase in plasma insulin levels (marker of insulin resistance) and
decrease in peripheral insulin sensitivity leading to decreased adipose
tissue and skeletal glucose transport (Ibrahim et al, 2005; Natarajan et al,
2005). Even as compared to SFA, TFA decrease the insulin sensitivity to a
far greater extent. Saravanan et al (2005) have reported that increasing the
linoleic acid (n-6 PUFA) in the diet, did not prevent the adverse effects of
TFA on insulin sensitivity, suggesting that it is necessary to reduce the
absolute levels of TFA. In addition SFA and TFA differentially alter the
expression of genes associated with insulin sensitivity in adipose tissues.
Compared to animal studies, human studies provided variable results on
TFA intake and insulin resistance (Thompson et al, 2011). Short term
human studies showed that among lean and healthy subjects, TFA intake
did not have significant effect on insulin resistance. The observation from
prospective cohort studies of TFA intake and type 2 diabetes risks have
been mixed (Thompson et al, 2011). Two studies showed no relation
between TFA consumption and type 2 diabetes risk, whereas another large
study showed significant positive association between TFA intake and
diabetes risk. However, TFA intake resulted in higher levels of plasma
53
insulin levels among individuals who were more predisposed to insulin
resistance, such as those with pre-existing insulin resistance, greater
adiposity or lower physical activity levels (Mozaffarian et al, 2009).
Further studies are required to confirm the effects of TFA on insulin
resistance and diabetes.
Health effects of TFA from Vanaspati: In a case control study in two
major Indian cities, an inverse association between mustard oil
consumption and IHD risk was seen, whereas a somewhat elevated risk
was observed with vanaspati consumption (Rastogi et al, 2004). As a large
proportion of the Indian population is predisposed to insulin resistance;
and the prevalence of diabetes and coronary heart disease is high,
reduction in TFA intake both through hydrogenated oils and the foods
consumed coupled with other dietary and life style changes, need to be
actively advocated.
Figure 2.9: Potential Physiological Effects of Trans Fatty acids
(Source; Mozaffarian et al, 2006)
54
Hypertension: Dietary intake of various fats may have different effects on
blood pressure. Experimental studies found that feeding rats with saturated
fatty acids resulted in impaired endothelial function (Gerber et al, 1999)
and enhanced sympathetic nervous system activities (Young et al, 1994)
which increased the blood pressure. In contrast, consumption of long-chain
ω-3 PUFAs modulated plasma phospholipid composition and cell
membrane fluidity, increased the production of vasodilators, and reduced
cardiac adrenergic activity (Valensi, 2005) all of which lowered the blood
pressure. Similarly the study by West et al, (2005) also showed that
MUFA also modified membrane phospholipids composition and vascular
reactivity the net effects could either raise or lower blood pressure.
However, direct effects of TFA on blood pressure remain largely unclear.
Due to the lack of flexible structure of their parent unsaturated fatty acid,
TFA display biological features more similar to SFA. Furthermore, since
TFA compete with other unsaturated fatty acids for enzymatic
desaturation, the presence of TFA may increase the demand for essential
PUFA (Kinsella et al, 1981).Studies linking fatty acids intake with incident
hypertension have yielded inconsistent results. In the Nurses’ Health
Study, a cohort of 121,700 US women aged 34-59 years (Witteman et al,
1989) and the Health Professionals Follow-up Study, with a cohort of
51,529 US men aged 40-75 years (Ascherio et al, 1992), no association
was found between baseline intake of SFAs, MUFAs, PUFAs, or TFA
assessed from food frequency questionnaire and incident hypertension
during a follow-up of 4 years. However, in a large-scale prospective cohort
study aimed to examine the association between intake of subtype and
individual fatty acids and the risk of developing hypertension among
28,100 women (aged ≥39 years and free of cardiovascular disease and
cancer), it was found that after adjusting for demographic, lifestyle, and
other dietary factors, higher intake of SFA, MUFA and TFA was each
positively associated with the risk of hypertension among middle-aged and
older women. The associations for SFAs and MUFAs were largely
55
attenuated by adjustment for potential intermediate factors including BMI,
diabetes, and hypercholesterolemia, while the associations for TFA
remained significant even after these adjustments. Intake of PUFAs was in
general not associated with the risk of hypertension.
Cancer: There are few studies investigating the relationship between
TFAs and certain cancers (Smith et al, 2009). The role of TFA in the
causation of cancers remains unclear. The EURAMIC study which
investigated the association between TFA content in adipose tissues and
the incidence of breast, prostate and colon cancer, demonstrated a positive
association between TFA and the incidence of colon and breast cancer but
not prostate cancer. In a case control study, serum TFA levels were
positively associated with the incidence of breast cancer. In another study
high consumption of TFAs was positively associated with distal colorectal
cancer (Vinikoor et al, 2010). Overall the role of TFAs in the causation of
cancer remains inconclusive and further studies are needed to establish an
association.
Liver Dysfunction: Trans-fatty acids are uniquely handled by liver i.e.
they are metabolized differently by the liver than other fats. In a study by
Mahfouz (1981) on the effect of dietary trans fatty acids on the delta 5,
delta 6 and delta 9 desaturases of rat liver microsomes in vivo it was
shown that the dietary trans fatty acids are differentially incorporated into
the liver microsomal lipids and act as inhibitors for delta 9 and delta 6
desaturases. The delta 6 desaturase is considered as the key enzyme in the
conversion of the essential fatty acids to arachidonic acid and
prostaglandins both of which are important to the functioning of cells
(Mahfouz, 1981). This indicates that the presence of trans fatty acids in the
diet may induce some effects on the EFA metabolism through their action
on the desaturases.
Non Alcoholic Fatty Liver Disease (NAFLD) occurs when fat is
deposition (steatosis) in the liver is not due to excessive alcohol use. It is
56
related to insulin resistance and the metabolic syndrome (Adams and
Angulo, 2006). Non-alcoholic steatohepatitis (NASH) is the most extreme
form of NAFLD which is regarded as a major cause of idiopathic cirrhosis
of the liver (Clark and Diehl, 2003). TFA consumption has been associated
with NAFLD. In an animal study, the livers of TFA-treated animals
contained larger vesicular structures consistent with
macrovesicularsteatosis (Collison et al, 2009). In this model, 30 per cent of
the dietary fat was in the form of partially hydrogenated vegetable oil, and
when this was replaced by isocaloric amounts of lard, the extent of
steatosis was substantially reduced, indicating greater liver injury with the
consumption of industrially produced TFA (Tetri et al, 2008). The highest
level of hepatic TG occurred in the TFA diet group with a 1.43-fold
increase in hepatic lipid content compared with control. Trans-fat feeding
increased serum leptin, and total cholesterol levels, while robustly
elevating hepatic lipogenesis and lipid catabolism. It was also associated
with increasing markers of inflammation, lipid storage, DNA damage, and
cell cycle impairment (Collison et al, 2009).
Infertility: Consumption of TFAs has shown to increase the risk for
ovulatory infertility (Bhardwaj et al, 2011a). In a prospective cohort study
of 18,555 married, premenopausal women without a history of infertility it
was concluded that dietary TFAs increased the risk of ovulatory infertility
when they replace carbohydrates or unsaturated fats that are commonly
found in vegetable oils. Dietary consumption of TFAs instead of MUFAs
was significantly related to the risk of ovulatory infertility. The
replacement of 2 en% from MUFAs with 2 en% from TFAs was
associated with a more than double risk of ovulatory infertility. Similarly,
the consumption of 2 en% from TFAs rather than from n - 6 PUFAs was
associated with a significantly greater risk of ovulatory infertility
(Chavarro et al, 2007). Further the intake of TFAs has been associated
with greater insulin resistance, risk of type 2 diabetes and concentrations
57
of inflammatory markers, which may also adversely affect ovulatory
function.
Complications in Pregnancy: High intake of dietary TFA have also been
associated with complications during pregnancy. A retrospective case
control study showed that pregnant women with high erythrocyte trans
fatty acids were at a much higher risk of preeclampsia than pregnant
women with low levels of the same (Williams et al, 1998). Similarly
another case control study also showed that erythrocyte TFA levels,
particularly the 18:2 trans, were positively associated with the risk of
preeclampsia (Mahomed et al, 2007). Further, increased fetal loss has been
attributed to high intake of TFAs possibly by down regulating the nuclear
transcription factor (PPARγ), which plays a pivotal role in placental
function (Morrison et al, 2008).
Fetal Development: The PUFA status of the developing fetus depends on
that of its mother, as confirmed by the positive relation between maternal
PUFA consumption and neonatal PUFA status. Researchers from the
MaastrichtUniversity in the Netherlands showed that consumption of
TFAs appeared to be associated with lower maternal and neonatal PUFA
status. In addition, the presence of TFAs in cord tissue was associated with
proportionally lower amounts of essential PUFAs, a reduced birth weight,
and a smaller head circumference (Hornstra, 2000).
TFA compromises fetal development. There is a significant negative
relationship between birth weight and the C18:1(trans-9) concentration in
maternal plasma phospholipids during early stages of pregnancy (Hornstra
et al, 2006). TFAs are known to impair the metabolism of n-6 and n-3
PUFA to long chain PUFA, therefore these may possibly have adverse
effects on fetal growth and development (Innis, 2006). In pre-mature
infants, plasma TFA level was inversely associated with birth weight.
Another study showed an inverse relationship between long chain PUFA
and TFA in cord blood lipids of full term infants. Similarly high maternal
58
intake of TFAs was inversely related to gestational age and birth weight.
TFAs may have adverse effects on growth and development through their
interference with essential fatty acid metabolism; direct effects on
membrane structures or metabolism, or secondary effect by reducing the
intake of the cis essential fatty acids either in the mother or the child
(Innis, 2006). The PUFA status of the developing fetus depends on that of
its mother, as confirmed by the positive relation between maternal PUFA
consumption and neonatal PUFA status. In lactating women, the dietary
TFAs tend to displace the essential fatty acids (linoleic acid and alpha-
linolenic acid) in human milk, and eventually the TFAs end up in the
plasma phospholipids and triglycerides of their breast-fed infants (Innis
and King, 1999). Since TFAs have a negative impact on PUFA
metabolism, it is important to minimize the consumption of TFAs during
pregnancy and lactation to prevent the adverse effects of TFAs on fetal as
well as neonatal (infant) growth and development.
Animal studies have shown that maternal TFA consumption may have
long term adverse effects on glucose-insulin homeostasis in the off-spring
too. Several studies have shown that high intake of TFAs during
pregnancy and lactation predisposes the off-spring to insulin resistance in
adult life. Studies have also shown that the mothers' hydrogenated
vegetable fat intake during pregnancy and lactation led to hypothalamic
inflammation and impaired satiety-sensing, which promote deleterious
metabolic consequences such as obesity, even after the withdrawal of the
causal factor. In other words, the effect remains even after the
consumption of the standard chow by the offspring. (Pimentel et al, 2011).
In another animal study examining the effects of several individual
trans18:1 fatty acid isomers on fat synthesis, and expression of lipogenic
genes in mammary and liver tissue in lactating mice revealed that milk fat
percentage was decreased by trans-7-18:1 and PHVO by 27% and 23%
respectively, compared with control group (Kadegowda et al, 2010).
59
High intake of TFA during pregnancy and lactation increases adiposity in
breastfed infants and their mothers. These adverse effects of TFAs on
adiposity are of major concern since the recent increase in incidence of
obesity, especially childhood obesity in India, could be attributed to an
increase in the consumption of fast foods. These findings strengthen the
importance of restricting the intake of TFA during pregnancy and
lactation.
Asthma and Allergy: Low intake of certain polyunsaturated fatty acids,
particularly n-3 and n-6 fatty acids, has been associated with the
development of asthma and allergies in children, but little is known
whether the configuration (cis or trans) of these fatty acids also plays a
role. In an international study on asthma and allergies in childhood, the
incidence of asthma, allergic cold and asthmatic eczema in children
aged 13-14 years was investigated in ten European countries (155
centres around the world).
A positive association was found between the intake of trans fatty
acids and these diseases. Such an association was not observed for
the intake of monounsaturated and polyunsaturated fatty acids (Weiland
et al,1999). In another prospective study, the associations between dietary
intake of fatty acids, antioxidants and relevant food sources of these
nutrients on the clinical manifestation of asthma in adulthood were studied
and it was concluded that even in adulthood a high margarine intake
increases the risk of clinical onset of asthma. The effect was stronger in
men than in women (Nagel and Linseisen, 2005)
Mental Health and Cognition: Evidence from prospective epidemiologic
studies have shown that higher intakes of saturated fatty acids and TFAs
since midlife, and lower polyunsaturated to saturated fat ratio are
associated with a faster rate of cognitive decline and it also might be
60
associated with neurodegenerative diseases (Morris et al, 2003; Morris et
al, 2006; Devore et al, 2009).
- Alzheimer's Disease: A study examining the associations between intake
of specific types of fat and incident Alzheimer disease suggested that the
intake of both trans fatty acids and saturated fats promote the development
of Alzheimer disease (Morris et al, 2003). In an invitro study it was
revealed that trans fatty acids compared to cis fatty acids increase
amyloidogenic and decrease nonamyloidogenic processing of amyloid
precursor protein (APP), resulting in an increased production of amyloid
beta (Aβ) peptides, main components of senile plaques, which are a
characteristic neuropathological hallmark for Alzheimer's disease (AD).
The study also showed that oligomerization and aggregation of amyloid
beta (Aβ) are increased by trans fatty acids. The mechanism identified by
this in-vitro study suggests that the intake of trans fatty acids potentially
increases the risk of Alzheimer’s disease or causes an earlier onset of the
disease (Grimm et al, 2011).
- Depression: Studies have shown a detrimental relationship between
dietary intake of TFA and the risk for developing depression, whereas
weak inverse associations were found for MUFA, PUFA and olive oil. In a
Mediterranean cohort study, a direct and potentially harmful association
was observed between TFA intake and the risk of depression. The
magnitude of this association was robust and persisted after several
degrees of control for confounding and several sensitivity analyses. The
study also demonstrated an inverse dose-response relationship for total
PUFA and MUFA intake. Further , in another study it was found that
people over six years who ate more of trans fatty acid containing foods had
a 48 per cent higher risk of depression than those who did not consumed
trans fatty acids (Sánchez -Villegas et al, 2011).
Adverse Impact on Quality of Life: Quality of life is a broad concept
that relates to all aspects of human life. Quality of life questionnaires have
61
become an efficient way of gathering data about peoples’ functioning and
well being. Also, the health status measures have been shown to be a
powerful predictor for chronic diseases and mortality over the long term in
clinical practice (Guyatt et al, 2007; Wannamethee et al, 1991). Further,
the ageing population has fostered the general concern for leading health-
related better quality of life. A study conducted by Ruanco et al (2011)
showed a harmful association between the highest intake of TFA and
several domains of health survey (SF-36 domains). The association
remained significant for the mental domains (except for mental health),
and bodily pain after controlling for potential cofounders including the
adherence to the Mediterranean diet. A possible explanation this finding is
that TFA promote endothelial dysfunction and increase the production of
pro-inflammatory cytokines that may interfere with neurotransmitter
metabolism and inhibit Brain-derived neurotrophic factor (BDNF)
expression among other physiological effects (Ruanco et al, 2011). BDNF
is a peptide critical for axonal growth, neuronal survival as well as
synaptic plasticity and function. Therefore, it is likely that the consumption
of foods containing TFA could increase the vulnerability to some mental
or neurological disorders or act negatively on mental quality of life.
2.5 RECOMMENDATIONS FOR DIETARY TRANS FATTY ACIDS
Several organizations have given recommendations for dietary TFA including the
National Academy of Sciences (NAS), which advises the governments of United
States and Canada on nutritional science for use in public policy and product
labeling programmes. The Dietary Reference Intakes formulated by NAS in 2002
for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and
Amino Acids have included their findings and recommendations regarding trans
fatty acids (Food and Nutrition board, 2005).These recommendations are based on
two key facts; firstly, "trans fatty acids whether of animal or plant origin are not
essential and provide no known benefit to human health"; and secondly, while
both saturated fatty acid and TFA increase the LDL-c cholesterol, trans fatty acids
62
also lowers the HDL-c cholesterol; thus increasing the risk of coronary heart
disease. Because of these facts and concerns, the NAS has concluded that there is
no safe level of TFA consumption. There is no adequate level, recommended daily
amount or tolerable upper limit for TFA. This is because any incremental increase
in trans fatty acids intake heightens the risk of coronary heart disease. Despite this
concern, the NAS have not recommended the elimination of TFA from the diet.
This is because TFA though in trace amounts, is naturally present in many animal
foods, and therefore its removal from ordinary diets might introduce undesirable
side effects and nutritional imbalances if proper nutritional planning is not
followed.
The NAS has, therefore, "recommended that TFA consumption be as low as
possible while consuming a nutritionally adequate diet" (Food and Nutrition
board, 2005). Similarly, the World Health Organization has tried to balance public
health goals with a practical level of TFA consumption, recommending in 2003
that TFA be limited to less than 1% of overall energy intake (PAHO/WHO Task
Force, 2006).
The US National Dairy Council has asserted that the TFA present in animal foods
are of a different type than those in partially hydrogenated oils, and do not appear
to exhibit the same negative effects (National Dairy Council, 2004). While a
recent scientific review agrees with the conclusion stating that "the sum of the
current evidence suggests that the public health implications of consuming trans
fatty acids from ruminant products are relatively limited", it cautions that this may
perhaps be due to the low consumption of trans fatty acids from animal sources
compared to the industrially produced (Mozaffarian et al, 2006).
63
Figure 2.10: Summary of the potential role of dietary Trans fatty acids on
human health and quality of life.
Compromis
ed Fetal
Developme
nt
Cognitive
Decline
Visceral
adiposity
Dyslipidemia
Systemic
Inflammation
Insulin
Resistance
Hypertension
The Metabolic
Syndrome
Type 2
Diabetes
Cardiovascular
Disease
Cancer
Infertility
Problems in
Pregnancy
Decreased
Quality of Life
Dietary
Trans
Fatty Acids
Asthma &
Allergies
Liver
Dysfunction
64
Due to paucity of data on dietary intake of TFA or their levels in food items India
had not formulated recommendations on TFA till 2009. Thereafter “Consensus
Dietary Guidelines for Healthy Living and Prevention of Obesity, the Metabolic
Syndrome, Diabetes, and Related Disorders in Asian Indians” was developed
wherein based on the WHO recommendation a level of <1% of total energy was
proposed for the Indians too (Misra et al, 2011). The same was recommended by
Indian Council of Medical Research (ICMR) and National Institute of Nutrition
(NIN) (ICMR, 2010). However, in the revised dietary guidelines for Indians-final
draft by the NIN/ ICMR (2011)there is an upward revision has been suggested
proposing that the energy contribution from TFA should be less than 2 en%
(Table 2.11).
2.5.1 Data on consumption patterns of Trans Fatty Acids
In developed countries such as Europe and North America, the average intake of
TFA varies between 2-4 en percent or between 5 -10 grams/ person/ day in a
commonly consumed daily diet providing 2000 kcal/day (Craig-Schmidt, 2006).
Data from developed countries report wide variation in the intake of TFAs ranging
from 0.5 en% (Greece, Italy) to 2.1 en% (Iceland) among men and from 0.8 en%
(Greece) to 1.9 en% (Iceland) among women, this works to nearly 1.2 to 6.7g/ d
among men and 1.7 to 4.1 g/d among women. Intake of TFA was lowest in
Mediterranean countries (0.5-0.8 en %). It was below 1 en% in Finland and
Germany (Table 2.12). Moderate intakes were seen in Belgium, The Netherlands,
Norway and UK and highest intake was observed in Iceland (Hulshof et al, 1999).
In European countries the intake of TFAs (mean ± s.d.) was reported as 2.40 ±
1.53 g/day for men and 1.98 ± 1.49 g/day for women (Van de Vijver et al, 2000)
whereas in Iran it was approximately 12.3 g/day (Table 2.12). Intake of TFA on a
typical American diet has been estimated to be between 8-15 g/day, although wide
variation exists between individuals (Khosla and Hayes, 1996; Mozaffarian et al,
2007).
65
Table 2.11: National/ International Recommendations for Dietary Trans
Fatty Acids
Organization Year Country Recommendation
for Dietary
Trans Fatty
Acids*
NAS 2002 Advisory for
Canada and
United States of
America
No adequate level
FAO/ WHO 2003 Global TFA <1 en%
Food and Drug
Administration 2006
2006 United States of
America
TFA intake be
reduced to <1% of
energy intake.
Health Council of The
Netherlands (Hunter et al,
2006)
2005 The
Netherlands
TFA intake as low
as possible. UL
1% energy
Consensus Dietary
Guidelines for Healthy
Living and Prevention of
Obesity, the Metabolic
Syndrome,
Diabetes, and Related
Disorders in Asian Indians
(Misra et al, 2011)
2010 India TFA <1 en%
ICMR/ NIN Nutrient
requirements and
recommended dietary
allowances for Indians
(ICMR, 2010)
2010 India TFA <1 en%
NIN revised recommended
dietary allowances
guidelines final draft (NIN/
ICMR, 2011)
2011 India TFA < 2 en%
*Total TFAs: from ruminants and partially hydrogenated vegetable oils
In India, however, data on dietary consumption of TFA are rather scanty (Misra
et al, 2009a). The main source of TFA in India is vanaspati (partially
hydrogenated vegetable oil) used as a cheaper substitute for “ghee” (clarified
butter). It is widely used in the preparation of commercially fried, processed,
ready to eat/ street foods/ Indian snacks/ sweets/ savoury items/ frozen/ pre-frozen
foods, packaged foods and premixed foods. Vanaspati accounts for nearly 10% of
66
the total production of vegetable oils and approximately 55% of vanaspati
manufactured in India is consumed mainly in Haryana, Punjab, Uttar Pradesh and
Himachal Pradesh where it is majorly used as a cooking medium (Ghafoorunissa,
2008). Estimates of TFA intakes in India during the past 2 decades, based on the
per capita availability of vanaspati ranged between 1.0 and 1.3 kg/ year
(Srinivasan, 2005), while the estimates of TFA based on edible fats and oil
supplies that were available in India in the 1980s (approximately 0.8 million
tonnes), and the population size in the said period, indicated an average
availability of 3g/ person/ day of vanaspati (Achaya, 1987). In North India, where
vanaspati is used as a cooking medium, the consumption can be as high as nearly
20 g/ person/ day. In Delhi, nearly 37% of the fats and oils market is for vanaspati
(Singh and Mulukutla, 1996).
In the bakery industry, vanaspati, butter and specialty fats (margarines,
shortenings, gels) account for 60, 20 and 10%, respectively, of total fat usage. The
indirect consumption of vanaspati through foods purchased at these outlets is not,
reflected in the National Sample Survey (1999-2000). However, while the direct
monthly per capita consumption range between 0.01 kg and 0.45 kg (average,
rural 0.06 kg/ per person/ month, urban 0.04 kg/ per person/ month). This survey
further indicated that vanaspati consumption as cooking oil is confined mainly to
four states: Haryana, Punjab, Uttar Pradesh and Himachal Pradesh (National
Sample Survey, 2001; Srinivasan, 2005). The TFA content of vanaspati, varies
widely depending upon the proportion of palm oil or its fraction used during the
hydrogenation process.
The consumption of foods containing vanaspati has increased in recent years. This
high intake of TFAs may be part of several changes in dietary and other life style
patterns among urban middle, upper middle and high-income groups contributing
to the present day high prevalence of diet-related chronic diseases. In recent years,
the intake of TFAs has increased due to increased consumption of fast foods,
ready to eat foods and bakery products which are usually prepared using
67
vanaspati. The limited data obtained indicate that TFA content of biscuits ranged
between 30 to 40% of the total fatty acids (Ghafoorunissa, 2008).
Table 2.12: Data on Dietary intake of TFA across countries
S.No Author Sample Location TFA Intake
1 Van de Vijver
et al, 2000
327 (men),
299(women)
Eight of
the
European
countries
Mean (+/-s.d.) TFA intake was
2.40+/-1.53 g/day for men and
1.98+/-1.49 g/day for women
(0.87+/-0.48% and 0. 95+/-
0.55% of energy, respectively)
2 Allison et al,
1999 11,258 USA
Mean percentage of energy
ingested TFA = 2.6%, mean %
of total fat ingested as TFA =
7.4%.
3 Mozaffarian et
al, 2007
7158 urban &
rural households
(35,924
individuals)
Iran
TFA accounted for 33% of fatty
acids or 4.2% of all calories
consumed (12.3 g/day).
4 Hulshof et al,
1999
-
14 of the
Western
European
countries
TFA intake ranged from 0.5%
(Greece, Italy) to 2.1% (Iceland)
of energy intake among men and
from 0.8% (Greece) to 1.9%
among women (Iceland) (1.2-6.7
g/d and 1.7-4.1 g/d,
respectively). TFA intake was
lowest in Mediterranean
countries (0.5-0.8 en %). It was
below 1% of energy in Finland
and Germany. Moderate intakes
were seen in Belgium, The
Netherlands, Norway and UK
and highest intake in Iceland.
5 Elias et al,
2002
60 pregnant
females Canada
Mean fat intakes (in
g/person/day) for the second and
third trimesters, respectively,
were: 85.8 and 73.9, total fat,
31.5 and 26.4 and TFA 3.8 and
3.4. Fat represented 28% of
dietary energy in both trimesters.
The major sources of trans-fatty
acids were bakery foods (33% of
trans-fatty acid intake), fast
foods (12%), breads (10%),
snacks (10%), and
margarines/shortenings (8%).
68
6 Sartika, 2011a 388 workers Indonesia
The mean intake of TFA was
0.48% of the total dietary
calories. Fried foods contributed
most to the total TFA consumed
at 0.20% of the total calories.
TFA intake from ruminant
products, and margarine/
hydrogenated vegetable oil
products were 0.09% and 0.06%
of calories, respectively. Every
additional 1% of SFA intake is
associated with an increase in
TFAs amounting to 0.03% of
total calories (r2=0.320, p=
0.000).
7 Castro et al,
2009
2,298 male and
female subjects,
including 803
adolescents (12
to 19 years), 713
adults (20 to 59
years) and
782 elderly
people (60 years
or over)
Brazil
The mean trans fatty acid intake
was 5.0 g/day (SE = 0.1),
accounting for 2.4% (SE = 0.1)
of total energy and 6.8% (SE =
0.1) of total lipids.
8 Yamada et al,
2010
225 adults (30 to
69 years) Japan
Mean total fat and trans fatty
acid intake was 56.9 g/day
(27.7% total energy) and 1.7
g/day (0.8% total energy),
respectively, for women and
66.8 g/day (25.5% total energy)
and 1.7 g/day (0.7% total
energy) for men.
9 Misra et al,
2009a
13-18 years
(n 797)
India
Mean TFA intake was 1.1 en %
(Males: 0-10.7; Females; 0-
10.2g/d)
18-69 years
(n 227)
TFA intake was1.0 en% for
males and 0.8 en % for females.
2.5.2 Global Regulations on Dietary Trans Fatty Acids
Regulation is a simpler and efficient way of reducing TFA intake than labelling
impositions, because it does not require campaigns educating consumers for the
negative health implications of TFA. Moreover, regulation also allows controlling
all type of products, including those from bakeries and restaurants and not only
the pre-packaged ones (Bysted et al, 2009).
69
Governments across the world have now made it mandatory to label the TFA
content along with other nutritive values on the nutrition label of commercially
prepared and packaged food items (Stender et al, 2012). The permitted level
ranges from <1% of the total calories by WHO (Uauy et al, 2009) to 2% of fats
and oils destined for human consumption by Denmark (Stender et al, 2006) (Table
2.13).
At International level, the World Health Organization recommended that fats for
human consumption should contain less than 4% of the total fat as trans and urged
the food industry to reduce the presence of TFA in their products to these levels
(Priego-Capote et al, 2007). However in 2003, WHO recommended that
governments around the world phase out partially hydrogenated oils if trans-fat
labelling alone doesn't spur significant reductions. WHO also recommended that
the trans fatty acids consumption should be less than 1% of the total daily energy
intake (WHO, 2003).
The experts acknowledged the current recommendation of a mean population
intake of TFA of less than 1en% may need to be revised in light of the fact that it
does not fully take into account the distribution of intakes and thus the need to
protect substantial subgroups from having dangerously high intakes. This could
well lead to the need to remove partially hydrogenated fats and oils from the
human food supply (FAO, 2008). The Centre for Food Safety closely monitors
the latest international developments regarding regulation of trans fatty acids.
The World Health Assembly resolved in 2004 that elimination of TFA
should be a key point for action by governments (WHO, 2004). WHO/ FAO
has recently completed an extensive review of latest research on the links of
TFA to CVD and diabetes and recommended that all countries should take urgent
regulatory steps to limit trans fatty acids in their diet so that clear danger to heart
health in vulnerable groups is avoided (Hunter et al,2006). Consumption of
trans fatty acids result in considerable potential harm with no benefit
(Mozaffarian et al, 2006).
70
The Codex Alimentarius Commission in its response to the WHO’s Action plan
for implementation of the global strategy on diet, physical activity and health
stated that "if the provisions for labelling of, and claims for, trans-fatty acids
do not affect a marked reduction in the global availability of foods
containing trans-fatty acids produced by processing of oils and by partial
hydrogenation, consideration should be given to the setting of limits on the
content of industrially produced trans-fatty acids in foods”. Further, it prohibits
the use of hydrogenated fats in foods meant for infants and children (FAO/ WHO,
2007).
In India several commercial food items with high TFA content are being sold by
food industry as well as roadside vendors; which is a matter of serious concern.
There are four major regulatory policy instruments used in India for
enhancing food safety; mandatory product standards; mandatory process
standards; licensing and prohibitions as well as voluntary product and process
standards. The edible oil industry is regulated under different standards.
a. Prevention of Food Adulteration Act, 1954: It includes specific standard on
edible oils giving broad specification for different oils [cottonseed, coconut,
groundnut, linseed, mahua, rapeseed, sunflower oil etc. and now in olive
(revised)]. It includes standards for blended vegetable oil, which allows
different oils to be blended and sold. However, the specifications do not lay
down any guidelines on the fatty acid composition of different oils. In
addition, there are specifications for vanaspati (hydrogenated vegetable oil).
Under this standard, companies can mix any quantity of any ‘harmless’ vegetable
oil in their brand in varied proportions. In September 2008, the ministry issued
notification for labelling of food, under the PFA. This notification includes
for the first time labelling for nutrition and health claims (PFA, 2008). For
edible oils, if the company makes nutrition or health claims, then it is required to
provide information on its package about the amount or type of fatty acids,
71
highlighting cholesterol, SFA, MUFA, PUFA and TFA contents. The PFA Rules,
1955 amended from time to time require that:
(a) The foods in which hydrogenated vegetable fats or bakery shortening is
used shall declare on the label that “Hydrogenated vegetable fats or bakery
shortening used-contain trans fatty acids”.
(b) A health claim of ‘trans fat free’ may be made where the trans fat is less than
0.2g per serving of food.
(c) A claim ‘saturated fat free’ may be made only where the saturated fat does not
exceed 0.1g per 100g or 100ml of the food.
b. The Bureau of Indian Standards (BIS) lays down different
specifications for edible oils and vanaspati. Giving requirements for physical
and chemical tests for moisture and insoluble impurities (per cent by mass),
Colour, Refractive index at 40ºC, Iodine value, unsaponifiable matter (per
cent by mass), Flash Point (ºC), heavy metals, aflatoxins and pesticides, free fatty
acid value expressed as oleic acid (maximum 5.0 and 0.25 per cent by mass for
raw and refined grades of materials), but no standard are laid for fatty acid
composition or trans fatty acids.
c. The AGMARK is a voluntary standard for Vegetable Oils and vanaspati
governed by the directorate of marketing and inspection of the Ministry of
Agriculture (Government of India) as per the Agricultural produce Grading
and Marking Act (1937). Blended Edible Vegetable oil and fat spread are
compulsorily required to be certified under AGMARK. However, it does not have
any standards for fatty acids or trans fatty acids. As regards SFA the limit has
been expressed as 0.1 g/ 100 g or 100 ml. However, in case of TFA value per
serving is required.
72
Table 2.13: Global/ Country Level Guidelines for TFA Consumption as well
as Food Labeling
Country Agency/ Year Guidelines
Global
WHO/ FAO, 2003
Global phase out of partially
hydrogenated oils (Hunter et al,2006)
Codex alimentarius, 2007
Prohibits the use of hydrogenated fats in
foods meant for infants and children.
Setting of limits on the content of
industrially produced trans-fatty acids in
foods (FAO/ WHO 2007).
Canada
Health Canada, 2005 Products with less than 0.2 grams of TFA
per serving may be labeled as free of
trans fatty acids (DCC, 2008).
Task force co-chaired by
Health Canada & Heart &
Stroke Foundation of
Canada, 2006
A limit of 5% TFA (of total fat) in all
products sold to consumers in Canada
(2% for tub margarines & spreads)
(HCHSFC, 2006).
United
States of
America FDA, 2003
FDA has declared label value for TFA as
0.5 g or less per serving. Products
entering interstate commerce on or after
January 1, 2006 must be labeled with
trans fatty acids. Food manufacturers
can list amounts of TFA with less than
0.5 gram (1/2 g) per serving as 0 (zero)
on the Nutrition Facts panel (FDA, 2003).
Denmark 2003
The limit for TFA is 2% of fats and oils
destined for human consumption. This
restriction is on the ingredients rather
than the final products. This has made it
possible to eat "far less" than 1 g of
industrially produced trans fatty acids on
a daily basis (Stender et al, 2006).
India Beauro of Indian
Standards (BIS)
No standard for fatty acid composition
or TFA (CSE, 2009).
Prevention of Food
Adulteration Act (PFA)
To provide information on the
package about the amount or type of
fatty acids, including cholesterol,
SFA, MUFA, PUFA and TFA (PFA,
2008). A health claim of ‘tran fat free’
may be made where the trans fatty acid is
less than 0.2g per serving of food.
AGMARK
It does not have any standards for
fatty acids or trans fatty acid. (CSE,
2009)
73
2.6 APPROACHES FOR LIMITING TRANS FATTY ACIDS FROM FOOD
SUPPLY
In order to successfully remove trans fatty acids from the food supply, an effective
alternative has to be brought in to practice, which can fulfill the requirements of
food manufacturers and is not a cause of concern for the consumer’s health.
Removing partially hydrogenated vegetable oils (PHVO) from the food supply
requires replacement with fats and oils of similar physical and sensory properties.
Most fats and oils consumed on a regular basis are a combination of several fatty
acids. Saturated fatty acids are by far more stable than polyunsaturated and
monounsaturated fatty acids. This stability plays an important role in improving
the shelf life of packaged foods and in retarding the rancidity of the oils including
the oils used for frying.
The major fatty acids found in food are palmitic, stearic, oleic, linoleic, and α
linolenic acids. Their structure, physical properties, functionality traits, and health
effects are summarized in Table 2.14.
2.6.1 Fats and Oils for Human Consumption
Identification of a suitable alternative to trans fatty acid containing fats/ oils
requires thorough understanding of their end use. Fats and oils for human
consumption vary in their fatty acid profile (Figure 2.11) and are usually separated
into 3 categories: cooking oils, frying oils and solid fats. The quality issues of
edible oils include oxidative stability, nutrient composition, and functionality.
Cooking Oils are required for the purpose of day to day cooking (sautéing/
vegetable preparation). Bland flavor, light color, good stability,
manufacturing processing and packaging flexibility are important for
cooking oils. Good choices to meet these requirements are polyunsaturated
and monounsaturated oils. Low PUFA oils are preferred to minimize the
likelihood of rancidity and the need for refrigeration. Cooking oils are also
suitable for deep frying at household levels however repeated frying can
deteriorate the quality of the oil. These oils contain very little of TFA
74
(mainly occurring during refining and deodorizing) however, repeated
heating/ frying at household level can increase the TFA content. To curb
the formation of TFA during frying, consumer need to be made aware of
the ways to limit the TFA content.
Frying Oils are mainly used forcommercial frying applications which
includes restaurant/ commercial frying such as the preparation of deep-
fried foods and packaged foods like chips/ namkeen’s/ other snacks etc.
Oils for commercial frying require stability related to the thermal
deterioration processes of oxidation, hydrolysis, and polymerization. For
consumer acceptance, the fatty acid composition of the oils needs to have
20% to 30% linoleic acid to produce a desirable full deep-fried flavor to
the foods; however, higher levels of linoleic acid might introduce “off”-
flavours from oxidation. For restaurant use, oils need to be stable because
a long fry life is required and the oil has to withstand the high temperatures
of commercial frying. Food manufacturers prefer stable oils that can also
tolerate high temperatures and allow an extended shelf life for foods after
they are packaged.
Stable frying oils are characterized by increased amounts of oleic acid
(preferably in the moderate range of 50% to 65%), decreased amounts of
linoleic acid (desirable between 20% to 30%), and decreased amounts of
α-linolenic acid (preferably no more than 3%). It has been common to
acquire stable commercial frying oils by changing the fatty acid
composition through partial hydrogenation.
75
Table 2.14: Major fatty Acids Present in Foods
Fatty Acid Structure Physical
Property Functionality Trait Health Effect
Palmitic
Acid C16:0 Saturated
Solid at room
temperature
Stable in
storage and
during frying
Used for
preparation of
margarines,
shortenings, and
spreads As a cream
base for baked
products Desirable
smooth mouth feel
Increases LDL
cholesterol and
elevates the risk for
heart disease
Stearic Acid C18:0 Saturated
Solid at room
temperature
Stable in
storage and
during frying
Relative large
percent
converted to
oleic acid
Used to form
margarines,
shortenings, and
spreads As a cream
base for baked
products Promotes
more of a grainy
mouth feel
Little effect on serum
cholesterol levels
because a high
proportion is
desaturated to oleic
acid
Oleic Acid C18:1
Monounsaturat
ed with
1 cis double
bond
Liquid at
room
temperature
Relatively
stable in
storage and
during frying
High stability
generally a positive
feature. Oils
containing very
high amounts of
oleic acid tend to
produce undesirable
fried-food flavor,
sometimes
described as bland
or waxy, caused by
a lack of breakdown
products
Lowers cholesterol
and may slow
progression of
atherosclerosis
Linoleic
Acid
(omega-6)
C18:2
Polyunsaturate
d with
2 cis double
bonds
Liquid at
room
temperature
Unstable in
storage and
during frying
Small amount is
acceptable to food
flavors
Inverse association
between n-6
polyunsaturated fatty
acids intake and the
risk of coronary heart
disease
α Linolenic
Acid
(omega-3)
C18:3
Polyunsaturate
d with
3 cis double
bonds
Liquid at
room
temperature
Unstable in
storage and
during frying
Main source of off-
flavors because of
its tendency to
oxidize and
contribute to
rancidity in
packaged and fried
foods
Increased
consumption of n-3
fatty acids from fish
or fish oil
supplements, reduces
the rates of all-cause
mortality, cardiac
and sudden death,
and possibly stroke
76
Potential alternatives to partially hydrogenated oils for commercial frying
include naturally stable oils such as corn, cottonseed, palm, peanut, and
rice bran or modified fatty acid oils such as mid oleic corn, high oleic/ low
α-linolenic canola, high oleic sunflower, mid oleic sunflower, low α-
linolenic soybean, and mid oleic/ low linolenic soybean oils. In choosing
trans fatty acid free frying oils, due consideration needs to be given to the
cost, availability, oxidative stability, functionality in terms of the
appearance and texture, flavour, and nutrient composition of the options.
Specifically, some of these oils such as animal fats and tropical oils
contain high amounts of saturated fats.
Figure 2.11: Complete Fatty Acid Profile of Commonly Used Fats &
Oils in India All the values are in %. *Source; Nutrient requirement and recommended dietary
allowance for Indians (2010); National Institute of Nutrition, Indian Council of Medical
Research.
92
68
39
19 17 16 12 9.6 12 14 4 6
15 10
47
6
29
46
48 44
41.6
37
15
25.8 26
67 62
75
21
49
2 2
11
32.6 38 42
50
75
62 53
15 22
9
16
4 1
0.4 0.4 1 0.4 1 0.4 0.2
7 14 10
1
53
SFA MUFA LA ALA
77
Solid Fats: Solid fats are required to be used as shortening and provide
structure and texture in baking and frying.Functionality parameters in solid
fats (vanaspati, ghee, butter, bakers shortening/ margarine and spreads)
include the melting point, lubricity, moisture barrier, and creaming ability.
The parameters of fat content, emulsifiers, solid fat in blending, and
melting point need to be in place before the product development is
initiated. In the development of solid shortenings to reduce trans fatty
acids, functional parameters such as plasticity for extrusion into dough and
creaming properties are important. The dough should not be sticky or “oil
out” at high temperatures. Solid shortenings packed in cubes need to allow
handling without deformation.
Partially hydrogenated fats have been effective in achieving functionality
and stability requirements in solid fats. To meet the functionality and
stability requirements in solid fats while minimizing trans fatty acids,
many of the current options typically include significantly increasing
saturated fatty acids. Several consumer brands of solid TFA free
margarines have become available in recent years, as have solid
shortenings. The availability of these products for commercial use is
uncertain at this time.
2.6.2 Considerations for Selection of Trans Fatty Acid Alternatives
When evaluating alternatives to reduce trans fatty acids in the food supply, several
points need to be taken into consideration:
There are several different needs like cooking/ frying/ baking/ fat for
shortening etc., therefore different solutions for oils. As a result, there
cannot be a single solution in terms of alternative oils.
There are various applications with different attributes, including sensory
needs, the level of nutrition benefit sought, and functionality.
Food companies might have brand claims or product positions that drive
decisions regarding the oil choices.
78
Availability and cost considerations are paramount before a conversion
can happen. When evaluating alternatives to reduce trans fatty acids in the
food supply, several considerations need to be made. The trait-enhanced
oils also face the numerous challenges such as:
- Additional costs are incurred. A grower premium is provided to
farmers as an incentive for them to grow trait-enhanced beans/ seeds
and to compensate the growers for their efforts at the segregation of
trait-enhanced from the commodity oil seeds. There are also additional
oil processor costs related to the need to collect, crush, refine, and store
the oil separately.
- in the development of new varieties of oil seeds, long lead time is
required. The decision about which specific seeds to grow is made
several years in advance of the oil delivery; thus, contract planting is
necessary.
2.6.3 Alternatives to Partially Hydrogenated Fat
In recent years there have been a number of strategies suggested to reduce the
consumption of TFA at both population and individual in many of the developed
nations. In principle it is considered important that TFA are replaced preferably by
cis unsaturated fats from vegetable oils rather than saturated fats from tropical oils
or animal fats. The concern of the severe negative impact of TFA on human health
has led food industry to make a clear effort to search for alternatives. Some of the
potential ways to limit/ replace TFA include:
a) Modification of the partial hydrogenation process to produce fats with low
TFA levels
b) Use of plant breeding and genetic engineering to produce oil seeds with
modified fatty acid composition
c) Use of tropical oils, for instance, palm oil, palm kernel oil, coconut oil
d) Interesterification of mixed fats. Interesterification is the hydrolysis of the
ester bond between the fatty acid and glycerol (Tarrago-Trani et al, 2006; Lee
et al, 2008).
e) Genetic manipulation of soybean oil is providing alternative oils, which are
more stable.
79
The details of these approaches have been summarized in Table 2.15.
In view of the present scenario to replace dietary TFAs, two practical options are
available, 1) revert to a natural saturated fat without cholesterol which is most
likely palm oil or its fractions or 2) move to a newer model of modified fat
hardened by interesterification. Both of these options have been the subject of
nutritional scrutiny for approximately the last 40 years, and both have positive and
negative attributes.
2.6.4 Learning from the success of the developed nations
A number of successful approaches have been used globally to reduce the TFA
content of foods and hence the intakes of TFAs. Among the examples reviewed,
several common features can be highlighted, which appear to be central to
implementing successful approaches to reducing TFAs. First is science, or expert
national panels, which reviewed the situation regarding TFA consumption in their
respective jurisdiction and made concrete recommendations for their reduction,
which were appropriate to the local environment. Second, the role and importance
of the media in facilitating change cannot be overlooked. Active interest by the
media in increasing consumer awareness of, and pressurizing industry to meet the
challenges associated with reducing the TFA content of foods was a central aspect
of the TFA reduction activities in Denmark, Canada, New York and in Argentina.
This awareness stimulated and sustained consumer demand, industry action and,
in many cases, government involvement to ensure continued product
reformulation by the industry. Governments have approached the problem through
a variety of measures, reflective of local circumstances, but all programmes have
exhibited a degree of government involvement, which has ranged from the
introduction of regulatory limits, for example, Denmark or New York; to the
introduction of agricultural and tax measures to support the production of healthy
alternatives, for example, Argentina; to setting concrete objectives, coupled with
active monitoring, and publishing industry progress over a defined time interval to
sustain the voluntary commitments by industry to reformulate, for example,
Canada. Thus, the complexity involved in TFA reduction and replacement
80
throughout the food supply makes it absolutely necessary for all sectors
(government, industry, public health and academics) to work collaboratively to
reach TFA reduction/elimination goals. These actions also need to be supported
by both media and consumer awareness of the health concerns associated with
TFA intakes to be successfully implemented.
Table 2.15: Alternatives to Partially Hydrogenated Fat
(Eckel et al, 2007)
Type of
Alternative
Description Examples Advantages Drawbacks
Tropical oils
Oils that come
from tropical
plants
Palm oil
Palm kernel
oil
Coconut oil
Functionality
Economics
Availability
Past user experience
Negative health
effect associated
with high
saturated fat
content
Animal fats
Fats that come
from animals
Beef tallow,
Lard, Butter
Functionality
Past user experience
Negative health
effect associated
with high
saturated fat
content and
naturally
occurring
cholesterol
Trait-enhanced
oils
New oil seed
varieties that can
yield oils that are
stable without
requiring
hydrogenation
Low-linoleic
soybean and
canola oils,
Mid oleic
soybean and
sunflower
oils
High-oleic
soybean,
sunflower,
and
canola oils
Many new varieties
have been
developed
or are in research
and development
pipeline
Generally
acceptable
functionality for
frying
Generally higher
costs
Long lead time
for delivery
Uncertainties
regarding
availability
Blending liquid
soft oils with
harder
components
Blending partially
hydrogenated
vegetable oils,
fully hydrogenated
vegetable oils
(with PUFA and
MUFA converted
to stearic acid), or
tropical fats with
liquid vegetable
oils
Company
specific
products
Individually
formulated to
provide various
fatty acid
compositions and
melting points.
Used for frying or
baking depending
on the fluidity of
the fat
Modified
hydrogenation
process
Increasing the
pressure,
decreasing the
temperature,
and/or changing
Company
specific
products
Can selectively
reduce the amount
of trans fatty acids
produced during
hydrogenation
Extremely high
pressure and
concentrations of
catalysts
required can
81
the catalyst or
catalyst
concentration to
lower levels of
trans fatty acids
In some cases, trans
fatty acid
production has been
suppressed by up to
80%
reduce
commercial
viability
Fractionation of
tropical fats
Separating palm
oil into hard
fractions to be
used as structuring
fats for margarines
and shortenings.
Dry multiple
fractionation yields
at firststage hard
stearin and mostly
unsaturated olein,
and yields several
other fractions at
later stages
Company
specific
products
Fractions with
different solid fat
profiles and melting
point curves to
allow
versatility in
formulation
Negative health
effect associated
with highly
saturated hard
fractions
(including
palmitic [C16:0]
and palm kernel
oil containing
C12, C14, and
C16)
Interesterificati
on
A liquid and a hard
stock (e.g. palm
kernel oil, solid
palm fraction) are
blended together
and interesterified
Involves treating a
fat with an excess
of glycerol in the
presence of a
chemical or an
enzymatic catalyst
at arelatively low
temperature,
causing the
rearrangement or
redistribution of
the fatty acids on
the glycerol
portion of the
molecule, thus
producing fats
with different
melting profiles
and physical
characteristics than
the parent fat
Company
specific
products
Does not change the
degree of
unsaturation of the
fatty acids
Does not convert
cis into trans
isomers
If an enzymatic
catalyst is used,
resulting
interesterification
process is
continuous and
specific, with
steeper solid fat
curves to provide
better functionality
and few
unidentified
byproducts without
the need for
extensive post
processing
High cost of the
enzymatic
catalyst
Technology has
not been fully
examined for its
effects on health
Current evidence shows that TFA intake adversely affects the health. In view of
the adverse effects of trans fatty acids on health of population at large we need to
search out for suitable alternatives and develop TFA free fats/ oils. The fried foods
are quite popular among all and have been part of our conventional as well as
82
modern diets, thus these will continue to stay in the market along with baked
foods and therefore will be an integral part of Indian diet. The regulatory
authorities need to formulate strict guidelines to limit TFA content in the food
supply. The food industry and the manufacturers need to be educated regarding
ways to avoid the formation of TFA in fats/ oils during processing/ food
preparation. Active media participation in generating awareness regarding the
adverse effects of trans fatty acids and their sources can educate the consumer,
which can further generate the demand for healthier foods free of trans fatty acids
and pressurize the food industry to meet the demand.