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DNT 200NUTRITION FOR HEALTH
SCIENCES
CARBOHYDRATE
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CARBOHYDRATE
Things sweet to taste prove in digestion sour.Shakespeare, King Richard II
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CARBOHYDRATE
DEFINITION
Carbohydrates are compounds composed of carbon, hydrogen
and oxygen arranged as monosaccharides or
multiples of monosaccharides (disaccharides & polysaccharides)
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CARBOHYDRATE
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Monosaccharides (single sugars)
Glucose– Also known as
• Blood sugar
• Grape sugar
• Dextrose
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Monosaccharides (single sugars)
Glucose (continued)
Plants capture the sun’s radiant energy and through photosynthesis, trap this energy in glucose
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Monosaccharides (single sugars)
Glucose (continued)– Is common to all disaccharides and
polysaccharides– Is the chief fuel of the body’s cells
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Monosaccharides (single sugars)
Fructose– Also known as levulose
– Is the sweetest of sugars
– The body can convert fructose to glucose or can break it into fragments from which fat can be made
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CARBOHYDRATESIMPLE CARBOHYDRATES
Fructose• Endocrine and metabolic effects include an increased risk
for insulin resistance and hyperinsulinemia• Common sources
– Sucrose– High fructose corn syrup
• Cheaper than sucrose• Represents the biggest change in our diets in the last 15 years• Used in sodas, juice boxes, bread, and a host of other foods
– Natural sweeteners high in fructose (e.g. honey) are not associated with the above cited negative changes
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Monosaccharides (single sugars)
Galactose– Does not appear singly in
nature
– Found only as a part of lactose
– During digestion, galactose is freed as a single sugar
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Disaccharides (double sugars)• Are pairs of single sugars linked together• A condensation reaction is one where two
reactants combine to yield a larger product such as when two monosaccharides link together to form a disaccharide and a molecule of water is created
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Disaccharides (double sugars)• A hydrolysis reaction is one where a major
reactant is split into two products such as when a disaccharide is cut in two with a molecule of water forming two monosaccharides
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CARBOHYDRATESIMPLE
CARBOHYDRATES
Disaccharides (double sugars)
Maltose– Consists of two glucose units
– Is a plant sugar -- is a minor constituent in a few foods to include malt and germinating cereals
– Also known as malt sugar
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Disaccharides (double sugars)Sucrose
– Most familiar of the three disaccharides
– Consists of one glucose unit and one fructose unit
– Also known as table or white sugar– Is usually obtained by refining the
juice from sugar beets or sugar cane to provide the brown, white, and powdered sugars
– Also occurs naturally in many fruits and vegetables
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Disaccharides (double sugars)
Lactose
– Consists of glucose and galactose
– Is the principle carbohydrate of milk
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CARBOHYDRATE
SIMPLE CARBOHYDRATES
Disaccharides (double sugars)Lactose
Lactose intolerance is the condition that results from an inability to digest the milk sugar lactose. It is characterized by bloating, gas, abdominal discomfort and diarrhea
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CARBOHYDRATE
COMPLEX CARBOHYDRATES
Energy Yielding Polysaccharides
Starch– Is the main storage material of
plants– Is composed of hundreds of
glucose units linked together– When you eat a plant, your
body splits the starch into glucose and uses the glucose for energy
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CARBOHYDRATE
COMPLEX CARBOHYDRATES
Energy Yielding Polysaccharides
Starch (continued)
Food Sources of Starch
– Grains (wheat, rice, corn, etc.)
– Legumes (peanuts, dry beans, dry peas)
– Root Vegetables (potatoes, yams)
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CARBOHYDRATECOMPLEX CARBOHYDRATES
Energy Yielding PolysaccharidesGlycogen
– Is the storage form of glucose– Also composed of glucose units -- more complex
than starch and highly branched
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CARBOHYDRATECOMPLEX CARBOHYDRATES
Energy Yielding PolysaccharidesGlycogen
– Not important as a food source of carbohydrate– Found in meats only to a limited extent -- does not
occur in plants– Made and stored by the liver and muscle tissues– Is the form in which the human body stores much of
its glucose
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CARBOHYDRATECOMPLEX CARBOHYDRATES
Non-Energy Yielding PolysaccharidesFibers
– Are the structural parts of plants– Are non-starch polysaccharides (and some non-
polysaccharides)– Not digested by human digestive enzymes (some are
digested by GI tract bacteria)– Can be classified as soluble or insoluble, depending
on their solubility in water
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CARBOHYDRATECOMPLEX CARBOHYDRATE
Non-Energy Yielding PolysaccharidesType of Fiber Major Food
SourcesAction in the Body
Soluble FibersGums, pectins,somehemicelluloses,mucilages
Fruits (apples,citrus), oats, barley,legumes
Delay GI transit (benefitsdigestive disorders)Delay glucose absorption(benefits diabetes)Lower blood cholesterol(benefits heart disease)
Insoluble Fibers
Cellulose, manyhemicelluloses,lignins
Wheat bran, cornbran, whole-grainbreads and cereals,vegetables (such ascabbage, carrots, andbrussels sprouts)
Accelerate GI transitIncrease fecal weight(promotes bowelmovements)Slow starch hydrolysisDelay glucose absorption
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CARBOHYDRATECOMPLEX CARBOHYDRATES
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CARBOHYDRATECOMPLEX CARBOHYDRATES
Non-Energy Yielding PolysaccharidesFiber Terminology
– Dietary Fiber -- Edible, non-digestible components of carbohydrates and lignin naturally found in plant food. Examples include cereal bran, flaked corn cereal, sweet potatoes, legumes
– Functional Fiber -- Fiber sources shown to have similar health benefits as dietary fiber, but are synthetic. Examples include pectin extracted from citrus peel and used as a food ingredient
– Total Fiber -- Dietary fiber + Functional fiber
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CARBOHYDRATECOMPLEX CARBOHYDRATES
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CARBOHYDRATE
CARBOHYDRATE METABOLISMStored Glucose
• Glycogen stored and released by the liver -- only a few hours worth is stored)
• Falling blood glucose signals that body cells need glucose -- liver cells dismantle glycogen into single molecules of glucose, which is released into the bloodstream
• Muscle cells can also store glycogen (about 2/3 of the body’s supply) but it is used by these cells for start-up and intensive exercise
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CARBOHYDRATE
CARBOHYDRATE METABOLISM
Using Glucose for Energy
• When glucose enters a cell, enzymes break it in half– The halves can be put back together again to make
glucose OR– Can be broken down into smaller fragments
• Fragments– Can yield energy when broken down completely into CO2
and water OR– Can be reassembled into units of body fat
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CARBOHYDRATE
CARBOHYDRATE METABOLISMMaking Glucose From Protein
Gluconeogenisis -- is when glucose is made from a non-carbohydrate source
• Making glucose from protein– Body protein can be converted to glucose
(gluconeogenisis)
• Body fat cannot be converted to glucose to any significant extent, although fat breakdown can yield energy for many of the body’s cells
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CARBOHYDRATE
CARBOHYDRATE METABOLISMMaking Glucose From Protein
• Only glucose can provide energy for:– Brain cells
– Other nerve cells
– Developing red blood cells
• Only adequate dietary carbohydrate can prevent the use of protein for energy -- this role of carbohydrate is known as its protein sparing action
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CARBOHYDRATECARBOHYDRATE METABOLISMMaking Ketone Bodies From Fat Fragments
Ketone Bodies -- the product of incomplete breakdown of fat when glucose is not available in the cells
• Inadequate carbohydrate may result in more fat being broken down -- but not all the way to energy
• Fat fragments combine with each other, forming ketone bodies– Muscles and other tissues can use ketone bodies for energy– When production of ketone bodies exceeds their use, they
accumulate in the blood causing ketosis, which disturbs the body’s normal acid-base balance
• 50-100 grams of carbohydrate per day spares protein and prevents ketosis
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CARBOHYDRATE
CARBOHYDRATE METABOLISMConverting Glucose to Fat
• Given more carbohydrate than it needs the body– Uses glucose for energy needs
– Fills glycogen stores to capacity
• Leftover is broken down by the liver (along with protein and fat fragments) into smaller molecules – Are then re-assembled as fat and stored
– A minor pathway compared to the conversion of dietary fat to body fat
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CARBOHYDRATE
BLOOD GLUCOSEMaintaining Homeostasis
Homeostasis -- the maintenance constant internal conditions by the body’s control systems
• Glucose must be maintained within limits that allow cells to nourish themselves– Too low and you become dizzy and weak– Too high and you become confused and have difficulty
breathing– Extremes left untreated can result in death
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CARBOHYDRATEBLOOD GLUCOSEMaintaining Homeostasis
Blood Glucose Regulators– Insulin -- a hormone secreted by the pancreas in response
to (among other things) increased blood concentration• Circulating insulin contacts the receptors in the body’s cells --
receptors respond by ushering glucose from the blood into the cells
• Most of the cells take only the glucose they can use for energy right away
• The liver and muscle cells can assemble the small glucose units into long branching chains of glycogen for storage
• The liver can also convert glucose to fat for export to other cells
• Thus, high blood glucose returns to normal as excess glucose is stored as glycogen and fat
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CARBOHYDRATEBLOOD GLUCOSE
Maintaining HomeostasisBlood Glucose Regulators (continued)Glucagon -- a hormone secreted by the pancreas
in response to low blood glucose concentrations that elicits the release of glucose from storage
• Glucagon signals the liver to dismantle its glycogen stores and release glucose into the blood for use by all the other body cells
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CARBOHYDRATEBLOOD GLUCOSE
Maintaining HomeostasisBlood Glucose Regulators (continued)
– Epinephrine -- a hormone secreted by the adrenal gland that modulates the stress response• Formerly called adrenaline• Acts quickly when a person experiences stress,
ensuring that all the body cells have energy fuel in emergencies
• Like glucagon, epinephrine works to return glucose to the blood from liver glycogen
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CARBOHYDRATE
BLOOD GLUCOSE
Maintaining HomeostasisBalancing within the Normal Range
– When blood glucose falls too low• Replenished by food
• In the absence of food, glucagon can signal the liver
to break down glycogen stores
– When blood glucose rises too high• Insulin can signal the cells to take in more glucose for
energy
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CARBOHYDRATE
BLOOD GLUCOSE
Maintaining HomeostasisBalancing within the Normal Range
– Eating balanced meals (abundant complex carbohydrates - including fiber, some protein, and a little fat) helps the body maintain a happy medium between the two extremes
• Fibers and fat slow down the digestion and absorption of carbohydrate enabling glucose to enter the blood gradually
• Dietary protein elicits the secretion of glucagon, whose effects oppose those of insulin
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CARBOHYDRATE
BLOOD GLUCOSE
Glucose Regulation
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CARBOHYDRATE
BLOOD GLUCOSE
Glucose Regulation
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CARBOHYDRATE
BLOOD GLUCOSE
Glucose Regulation
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CARBOHYDRATE
BLOOD GLUCOSE
Glucose Regulation
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CARBOHYDRATEBLOOD GLUCOSEMaintaining Homeostasis
Falling outside the Normal RangeIn some people, blood glucose regulation fails
• Diabetes– Insulin Dependent Diabetes Mellitus (IDDM) -- body fails
to produce insulin» Less common» Also known as Type I Diabetes or juvenile-onset diabetes
– Non-Insulin Dependent Diabetes Mellitus (NIDDM) -- cells fail to respond to insulin
» More common» Also known as Type II Diabetes» Is usually milder than IDDM and progresses
more slowly
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CARBOHYDRATEBLOOD GLUCOSEMaintaining Homeostasis
Falling outside the Normal Range (continued)
• Hypoglycemia -- an abnormally low blood glucose concentration
– Failures in blood glucose regulation are due to abnormalities in the body’s regulatory system, which alter the way that it responds to foods
– That is, food does not govern the blood glucose level -- the body does
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CARBOHYDRATE
GLYCEMIC EFFECT• Is a measure of the extent to which a food, as
compared to pure glucose, raises the blood glucose concentration and elicits an insulin response
• Refers to:– How quickly glucose is absorbed after a person eats– How high the blood glucose rises– How quickly it returns to normal
• Different foods foods have different effects on blood glucose
• Effect differs depending on whether the food is eaten alone or as a part of a meal
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CARBOHYDRATEGLYCEMIC INDEX OF SELECTED FOODS
Low (best) Moderate (better) High (good)Grains
Pumpernickel bread Sourdough bread White breadPasta Short-grain riceBran cereals Shredded Wheat Cornflakes
WafflesVegetables & Legumes
Soybeans PotatoesLentils CarrotsBaked beans
FruitsPeaches Banana WatermelonApples (& apple juice) PineappleOranges Orange juice
Milk ProductsMilk, Yogurt Ice cream
SweetsChocolate Jelly beans
Soft drinksHoney
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CARBOHYDRATEGLYCEMIC EFFECT
• Pros & Cons– Lowering the glycemic index of of the diet reduces insulin
secretion and improves glucose and lipid metabolism– May help prevent heart disease and diabetes– May help prevent obesity– Prolongs the presence of food in the digestive tract thus providing
greater satiety and diminishes the insulin response– Is complicated to teach– Relatively few foods have had glycemic index determined– Information is neither intuitively apparent nor printed on food
labels– Concern that consumers will adopt a low carbohydrate diet
instead of a low glycemic one
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CARBOHYDRATEAdded Sugars in the US Diet
Soft Drinks33%
Sugars & Candy16%
Sweetened Grains19%
Fruit Drinks10%
Milk Products9%
Cereals4%
Other beverages
4%
Others5%
Soft DrinksSugars & CandySweetened GrainsFruit DrinksMilk ProductsCerealsOther beveragesOthers
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CARBOHYDRATE
HEALTH EFFECTS
Sugar– In the amounts people currently
consume, sugar carries no proven health risk (FDA and National Academy of Sciences Data)
– Obesity -- sugar can contribute to obesity but does not, by itself cause obesity
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CARBOHYDRATE
HEALTH EFFECTS
Sugar (continued)
– Diabetes• Body fatness seems to be more
related to diabetes than diet is• Obesity is a major factor in the
causation of Type II diabetes• Sugar may be a causative factor
only if and when it contributes to obesity
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CARBOHYDRATE
HEALTH EFFECTS
Sugar (continued)
– Heart Disease• Fat, not sugar, is
clearly the major dietary culprit
• Moderate sugar intake does not influence the risk of heart disease
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CARBOHYDRATE
HEALTH EFFECTS
Sugar (continued)
– Hyperactive Behavior in Children• No sugar link confirmed by scientific
research• Sugary foods may replace nutrient-dense
foods causing nutrient deficiencies -- and deficiencies can cause adverse behavior
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CARBOHYDRATE
HEALTH EFFECTS
Sugar (continued)– Dental Caries
• Evidence says there is a relationship --however ANY carbohydrate-containing food can support bacterial growth
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CARBOHYDRATE
HEALTH EFFECTS
Sugar (continued)– Dental Caries
• Bacterial growth produces acid that eats away the enamel causing dental decay
• Level of dental caries seems to be more related to the frequency of sucrose intake than the quantity of sucrose ingested
• Retentive solid forms of sugar appear to be more cariogenic than liquid forms of sugar
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CARBOHYDRATEHEALTH EFFECTS
Complex Carbohydrates– Because diets high in carbohydrates (and low in
concentrated sugar) are also usually low in fat and energy and high in fiber, vitamins and minerals, health benefits area realized in the reduced risk of:
• Obesity• Cancer• Cardiovascular Disease• Diabetes• Dental Caries• Malnutrition
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CARBOHYDRATE
HEALTH EFFECTS
Fiber– Weight Control
• Fiber contributes little energy & promotes a feeling of fullness as it absorbs water
• Diets high in fiber-rich foods can promote weight loss if these foods displace concentrated fats and sweets
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CARBOHYDRATE
HEALTH EFFECTS
Fiber– Constipation, Hemorrhoids
• Some fibers attract water into the digestive tract thereby softening the stool
• Water-insoluble fibers (such as cellulose) contribute undigested residue in the digestive tract thereby enlarging the stool
• Large soft stools ease elimination for the rectal muscles
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CARBOHYDRATEHEALTH EFFECTS
Fiber– Appendicitis
• Prevents compaction of the intestinal contents
• Compaction could allow the appendix to become obstructed and permit bacteria to invade and infect it
– Diverticulosis• Stimulates the muscles of the digestive tract• Muscles retain their strength and resist bulging
into pouches known as diverticula
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CARBOHYDRATE
HEALTH EFFECTS
Fiber– Colon Cancer
• Populations consuming high-fiber diets generally have lower rates of colon cancer
• Fiber may prevent colon cancer by diluting, binding, and rapidly removing carcinogens
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CARBOHYDRATE
HEALTH EFFECTSFiber
– Heart Disease• Some fibers bind with bile (the emulisifyer that
assists with cholesterol and fat absorption)• With less bile available, fat and cholesterol
absorption diminishes and blood lipid concentrations decline
• Blood cholesterol levels decline further as the liver makes more bile from cholesterol to replace the bile bound to fiber and excreted
• Products of fiber digestion, once absorbed, also inhibit cholesterol synthesis
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CARBOHYDRATEHEALTH EFFECTS
Fiber– Glycemic Response and
Diabetes Control• Some fibers can trap nutrients
and delay their leaving the stomach for the small intestine
• Glucose absorption is thereby slowed, eliciting a moderate insulin response and a moderate rise in blood glucose
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CARBOHYDRATE
HEALTH EFFECTS
Fiber– Negative Health Effects
• May displace energy- and nutrient-dense foods
• When fiber intake is increased too rapidly, intestinal discomfort and gas may be experienced, therefore, increase gradually and be sure fluid intake is adequate
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CARBOHYDRATE
HEALTH EFFECTS
Fiber– Not All Fibers Have Similar Effects
• Wheat bran (composed of mostly insoluble cellulose) has no cholesterol lowering effect while oat bran (soluble) pectin (soluble) do
• Wheat bran is an effective stool-softening fiber
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CARBOHYDRATE
RECOMMENDED INTAKES
SUGARS AND STARCH
DIETARY REFERENCE INTAKE VALUE
• EAR– 100 grams (for brain glucose utilization)
• RDA– 130 grams (for brain glucose utilization)
• Distribution range for healthy diets– 45% - 65% of total Calories
2002 Data
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CARBOHYDRATE
RECOMMENDED INTAKES
FIBER
DIETARY REFERENCE INTAKE VALUE
• AI– Men under 50 -- 38 grams
– Men over 50 -- 30 grams
– Women under 50 -- 25 grams
– Women over 50 -- 21 grams
For greatest protection against coronary heart disease2002 Data
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CARBOHYDRATE
ALTERNATIVES TO SUGAR
ASPARTAME
• Sold as Nutrasweet
• L-alpha-aspartyl-L-phenylalanine methyl ester
• Major consideration is in the use of aspartame in children is in patients with autosomal recessive phenylketonuria
• Seizures, headache, nervousness, dizziness, memory impairment, nausea, temper outbursts, and depression are potential side effects but little controlled documentation exists
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CARBOHYDRATE
ALTERNATIVES TO SUGAR
Saccharin
• O-toluene sulfonamide derivative
• High consumption in infants is associated with irritability, excessive tone of the skeletal muscles, insomnia, spasms, and strabismus (a deviation of the eye)
• No longer associated with cancer risk in humans
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CARBOHYDRATE
ALTERNATIVES TO SUGARSucralose
• Sold as Splenda and marketed Fall 2000
• A chlorinated sucrose derivative
• Small risk for shrunken thymus glands (up to 40% shrinkage) and enlarged liver and kidneys
• Breaks down into small amounts of 1,6-dichlorofructose (a chemical which has not been adequately tested in humans and might pose cancer or neurological risk
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CARBOHYDRATEALTERNATIVES TO
SUGARStevioside
• Sold as Stevia
• Natural sweetener extracted from the leaves of Stevia rebaudiana
• Little risk for mutagenicity or carcinogenicity
• Suited for both diabetics, and PKU patients, as well as obese persons intending to loose weight by avoiding sugar supplements in the diet
• No allergic reactions to it seem to exist
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CARBOHYDRATE
ALTERNATIVES TO SUGAR
Sugar Alcohols• Natural sugars with Calories• Examples -- sorbitol, mannitol, xylitol • Slow absorption• 60+ grams per day can be hazardous to
diabetics -- liver converts the excess to simple sugar (a problem if not enough insulin is produced)
• Even with no blood sugar abnormalities, the increase in glucose can hormonally alter insulin and glucagon levels to limit fat release
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CARBOHYDRATE
ALTERNATIVES TO SUGAR
Tagatose• D-Tagatose
• Is a levo-sugar (left-handed sugar)
• To the tongue, tastes just like regular sugar
• Body cannot digest it
• Ingestion of large amounts may result in GI distress including diarrhea, nausea, and flatulence
• Marketed as Naturlose