Sugars, Sweetness, Money, Health

You may have heard the corn processor’s advertisement refrain “sugar is sugar”. In fact there are many

kinds of sugar. Lactose is a sugar; most of the adult people in the world have trouble processing lactose

for energy. Glucose is a sugar; it does not taste as sweet as table sugar (sucrose); it is one of the major

energy commodities in most of biology. Fructose is a sugar; it is found in honey, peaches, and fruits of all

kinds and is also a major commodity in biology. Maltose is one of the main sugars that yeasts like for

making bread or beer, but other yeasts like to make wine from fructose. Indigestible fiber and digestible

carbohydrate are both made of glucose units just stuck together in different ways. Even sucrose

obtained naturally from beets and sucrose obtained from sugar cane are slightly different; they have

different isotopic carbon ratios (that is different amounts of carbon-12 and carbon-13) by virtue of the

different photosynthetic pathways employed by the two different plants. Indeed sugar and

carbohydrate chemistry is rich, perplexing, and fruitful. Sugar economics are even weirder.

On one hand, some folks demonize fruit sugar (fructose) present in high fructose corn syrup (HFCS)

without really understanding what it is or where it comes from. Fructose is so named because it is

present in fruits. It is also present in nectar. So when we consume honey (see that link for a detailed

description of the composition of honey) or fruits or fruit juices of any kind we are consuming fructose

along with other trace components. It is challenging to reconcile the worship of honey as a health food

and the demonization of HFCS as a poison; there may be something there…just don’t know what yet.

On another hand, there are some data which suggest that all sweetness, but fructose in particular since

it is really sweet and really cheap, can upset the human sense of satiety. Like salt and probably many

other food components, sweetness can perhaps be habit forming and lead to appetite disregulation in

addition to abnormal blood sugar levels and caloric intake (see this article archive at the NIH :

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2892765/).

To become a little conversant in the language necessary to consider this inquiry in detail we must

consider some topics in organic chemistry, biochemistry, and historic trade regulation. Then you can

begin to make some more informed choices.

It is clear that as technology has enabled us throughout history, most folks have chosen to consume

more sugars of all types. This increasing consumption of one or more sugars (or refined carbohydrate)

may have significant health effects.

Let’s first consider a few facts (we’ll cover details later):

1. Fructose is the major sugar in fruit and honey and high fructose corn syrup (HFCS); it is often

accompanied by glucose (another sugar) in solution as separate molecules;

2. Sucrose (table sugar) comes from beets and sugar cane; Sucrose is made of glucose plus

fructose linked molecularly into a single molecule; it decomposes into glucose and fructose.

3. Glucose syrup can be economically made from corn;

4. Fructose is sweeter than most other sugars to the human nervous system (or tongue) (but there

are sweeter things);

5. Sucrose prices have been historically supported in the U.S. above that of world sucrose prices;

6. Glucose in corn syrup can be isomerized (rearranged) to make fructose and thus HFCS; this

sweetener is cheaper than sucrose in the United States;

7. Many folks blame consumption of fructose (from corn syrup) for a variety of ailments including

obesity and diabetes; however consumption of all types of sugar is increasing with time.

Some interesting questions are “Is consumption of large quantities of sucrose any more or less

dangerous than consumption of large quantities of fructose?” How about glucose? How about maltose?

How about lactose? How about galactose? Is there some insidious component in high fructose corn

syrup that is not present in honey or concentrated fruit juice? Where does the name “high fructose corn

syrup” come from? Is there a “low fructose corn syrup”? Is the increasing consumption of refined sugar

of all types causing malady? Do non-caloric sweeteners provide a positive alternative?

We will not answer all those questions, but rather will provide some data and some tools that will

enable you to consider the questions in more detail on your own. We will be concise and link to

authoritative external sources for in depth discussion where possible and potentially boring. Links to

external propaganda will be flagged as such.

History and Economics of Sugar Production in the United States

The central theme here is that the United States has propped up prices for internal sucrose production

from sugar beets or sugar cane through several means since 1789. For a concise history of these

programs you may refer to the University of Florida’s IFAS (Institute of Food and Agricultural Sciences)

Publication “The History of US Sugar Protection”. There are additional resources for understanding sugar

cane economics in particular at that site. The U.S. has not been alone in sugar price regulation; sugar

smuggling and price fixing (Germany, 2014) are very lucrative endeavors in many economies.

In recent years sucrose prices have been supported by a USDA loan program to cane or beet producers.

In a few years from 1789 to the present, there has been little or no intervention by US government

programs mostly because of political dispute. Nonetheless, US prices for sucrose have often been

significantly higher ( see figure below) than the world price. At present (2014) world prices and US

prices for sucrose have become more nearly equal. That sort of thing seems to happen with

commodities when prices are high. This paper from the United States Department of Agriculture

Economic Research Service provides a brief analysis of important factors in sugar prices since 2009.

Historical Wholesale Sucrose Prices. The top two plots (red and blue) are US prices. The bottom two

plots (green and purple) are world prices.

Data from the USDA Economic Research Service

At the retail level at the end of 2013, a 4 pound bag of sucrose costs 3.00 $US in rural south Georgia US;

that same bag of sugar costs 4.50 $US in Oslo, Norway (maybe the most expensive city in the world).

The grocery price indices in Oslo and the US differ by a factor of two; thus sucrose in the retail US

market is 33% more highly priced relative to other grocery items than in the Oslo market. That situation

is probably a market low for the U.S. sugar price relative to world prices.

The Corn Syrup Solution

Corn is a dominant crop in the United States. Take a walk through rural Iowa sometime if you don’t

believe it. The corn producers and processors have been very ingenious at finding multiple markets for

their crops including food, fuel and drink ethanol, structural starch, and fructose sweeteners. You can

read about the history of the multiple uses of corn here according to the corn industry.

The corn industry has also been successful at lobbying for corn subsidies from the USDA. An important

period for corn subsidies and high fructose corn syrup development was the oil embargo era of the early

1970’s. During that time, food prices rose dramatically in the U.S. in accordance with fossil fuel prices.

Pressure was felt by political entities for cheaper food. You may be interested in this documentary

about the history of U.S. corn production and subsidy.

So, the U.S. regulatory policies have had the effect of making sucrose from beets or cane expensive and

making corn cheap. Hence why not make sweeteners from corn? The problem is that corn is just not as

sweet as fruit or honey. Have a taste of corn syrup (in the U.S. a common brand is Karo). The sugar in

this corn syrup is glucose and perhaps maltose or dextrose (both of those are just glucose molecules

bonded in a specific way). These are sweet and useful for disrupting crystallization of sucrose when

making confections (this is why you put a tablespoon of corn syrup in candies or cake frosting), but they

are not as sweet as fructose.

So how can we make something sweeter from corn syrup? That is why we need to look at a little

chemistry.

Structural Chemistry

We have bandied about these names of sugars without really considering how they are different from

each other. A sugar is a small carbohydrate molecule. The name carbohydrate should give you a clue to

its chemical composition; (carbon, hydrogen, and oxygen often in a ratio of 1:2:1). Commonly

consumed, so-called “simple sugars”, have 6 carbon atoms. These include fructose, glucose, galactose,

mannose and many others. You may peruse the structures of many simple hexoses and their oligomers

(when you stick several together to make a larger sugar) here.

There are many other sugars with more or fewer than six carbon atoms. You may have heard of ribose in

the context of genetic material; it is a pentose. Similarly there are dioses, trioses, tetroses, heptoses and

so on.

We illustrate here the structures of D-glucose, L-glucose, D-fructose, and D-galactose. These are

monosaccharides. They all contain six carbon atoms. They are hexoses. This is a lot of information to

take in. Remember to think of the molecules as tinker toy sets; carbon atoms make four links; oxygen

atoms make two links; and hydrogen atoms make one link.

The common factors in all sugar structures are the presence of a chain of carbon atoms linked to each

other, one aldehyde or ketone group (these are the ones with the carbon = oxygen double bonds), and

alcohol groups (OH’s) on all other carbons.

D-Glucose L-Glucose D-Galactose D-Fructose

This figure above shows so-called Fischer projections of the structures of D-glucose (dextrorotatory or

right-handed) and L-glucose (levorotatory or left handed), D-galactose, and D-fructose. There are many

more hexoses possible and slightly fewer common in nature, but these four molecules illustrate a few

points before we go on to more complicated sugars.

1. The D (dextrorotatory) and L (levorotatory) nomenclatures are illustrated by the difference

between L-glucose and D-glucose. Study those two diagrams for a little bit. Then study D-

galactose and D-fructose. What is the common feature for the D molecules? It is the handedness

or clockwardness of the orientation of groups around the red carbon (number 5) atom. This

handedness makes a difference. L-glucose is not found in higher life forms. Although expensive,

it can be synthesized in the laboratory and tastes like D-glucose; but it cannot be processed to

provide energy in higher life forms. More generally, stereochemistry refers to differing three-

dimensional structures of molecules that have identical atomic connectedness. Although

obsolete in many regards, the D and L nomenclature persists in sugar and carbohydrate

chemistry; all nomenclature is arbitrary but becomes obsolete when not useful.

2. The carbon-oxygen double bond (C=O) can be located at the end or at the second from the end

carbons in most natural sugars. Other locations are possible, but are not common in nature. In

the case of a terminal C=O, the molecule is called an aldohexose because one of the carbon

bonds is to a hydrogen atom. In the case of a C=O in the middle of the chain, the molecule is

called a ketohexose because the carbon atom is bonded to two other carbon atoms. Notice that

fructose is a ketohexose and that glucose is an aldohexose.

3. Then notice the difference between D-glucose and D-galactose. It is the difference in

orientation of alcohol (OH) groups down the chain of carbon atoms. These differences can lead

to eight different D-aldohexoses (plus eight different L-aldohexoses) and four D-ketohexoses

(plus four L-ketohexoses).

Making Rings

To further complicate matters, the structures shown are just a start; six-carbon sugar molecules can

readily condense into ring structures in several different ways; two of those ways are commonplace.

This condensation can be reversible in solution, but the structures can be frozen into place when

crystallized or reacted with other molecules.

Let’s just consider ring formation in two molecules D-glucose and D-fructose, since these will be

important later. You may wish to extend this exercise to galactose and mannose, since those are also

biologically significant sugars.

alpha-D-glucose beta-D-glucose

These diagrams are side views of the hemiacetal forms of D-glucose (called glucopyranose). The

diagrams are meant to help the viewer understand the geometry and are sort of standard (called

Haworth projections or diagrams) in sugar chemistry; the thickness of the lines is meant to indicate

perspective. The C-H bonds are not shown; so if a C has fewer than four bonds there is an H out there in

the offing. The difference between the two forms is the orientation of the OH group at the number one

carbon. You may study some details of the mechanism by which those rings form here. Interconversion

between forms of glucose is facilitated by the presence of water and acid.

As you may have wondered, the ring formation or cyclization does not necessarily have to proceed to

form six-membered rings; but five or six membered rings are sort of favored in nature. Fructose can

form five membered rings; alpha and beta D-fructose (called fructofuranose in the ring form) are shown

in the figure below.

alpha-D-fructofuranose beta-D-fructofuranose

Disaccharides, Oligosaccharides, Carbohydrates, and Cellulose – linking the rings together

Sucrose

This is the sugar that we commonly call table sugar. It is produced by sugar cane and sugar beets and a

few other plants. Note that it consists of one glucose unit and one fructose unit bonded together. The

way in which they are bonded together and the stereochemistry (alpha or beta) of the individual units

are important. (If you are intrigued by learning more about stereochemistry, I recommend this pictorial

guide; it alludes to topics that will be important later in this study and emphasizes the sensitivity of

biological phenomena to the specific three-dimensional configurations of molecules.) To get back to the

topic at hand, the glucose-fructose (to make sucrose) linkage occurs between the number one carbon of

alpha-D glucose and the number two carbon of beta-D-fructose; in that process one molecule of water is

liberated. This molecule is stable in water, but if you add a little acid and warm it up – like in your

stomach for example or when making jam on the stove – it may readily decompose into individual

fructose and glucose units. This process is called inversion because, historically, one measureable

difference in the starting material and the final product was their differing tendency to rotate polarized

light. The product is called invert sugar; it is just a mixture of glucose and fructose in solution (much like

fruit juice, honey, or HFCS). It is sweeter than sucrose and does not form crystals as easily; for those

reasons it has been prized in baking.

The sucrose molecule. It is a combination of glucose and fructose in a specific way so that it does not

readily bond to any more sugar units.

Maltose, Starch, Glycogen, and Starch

Glucose is a common commodity in biology. When it links together in alpha 1,4 configurations like

below, we have maltose.

But it can be linked together in a few other ways to form amylose and amylopectin (plant starches),

glycogen (animal energy storage), and Cellulose (structural material) (shown below).

How Do We Make Fructose from Glucose?

It has been known since the ninth century that starches can be converted to produce sweet flavors. For

a brief history of the variety of sweeteners (including HFCS) that have been produced from starch, you

may refer to this report from UC Davis.

Methods for breaking down starch or oligosaccharides into simple sugars include both acid hydrolysis

and enzymatic degradation. You may have done this experiment when you were a child in school: chew

a saltine cracker for several minutes without swallowing; enzymes in your saliva start to break down the

starch in the cracker and release glucose; the cracker begins to taste sweet.

Alternative Sweeteners

You will note that in many of the synthetic or alternative sweeteners listed below other atomic

constituents appear, specifically chlorine (Cl), nitrogen (N), and sulfur (S). As a rule of thumb when

looking at these structures it is good to keep in mind that chlorine makes one bond, nitrogen makes

three bonds, and sulfur makes six bonds.

You may note that many of these compounds were discovered accidentally; indeed much of life is just

showing up.

As you peruse the structures of these sweeteners you may wish to consider the features that they might

have in common that serve to stimulate the human sweetness receptors. You might also marvel at how

exquisitely sensitive is the human sense of taste that it reveal subtle bitter flavors, slower sweetness

onset, and different aftertastes in nearly all of these alternative sweeteners. The human sense of taste

is also quite sensitive to stereochemistry.

Cyclamate

Saccharin

Stevia

Aspartame

Wikimedia commons image

Neotame

Wikimedia commons image

Sucralose

Acesulfame

Xylitol

There are several other alternative sweeteners available, and more are being discovered; but these are

some of the most economically significant.

Questions for Discussion

1. Can you identify any common structural features in alternative

sweeteners?

2. Are there reasons that HFCS might be more dangerous than honey?

3. Why do you think that Sucralose is non-nutritive?

4. Why doesn’t cellulose taste sweet?

5. Is sweetness addictive?

6. What are the prices of sweeteners per sweetness? Is there a sweetness

index?

7. What other desirable properties than sweetness does sucrose impart to

foodstuffs?

8. Which alternative sweetener would you choose if in a bind?