The Carbohydrates Sugars Starches Fiber Copyright 2005 Wadsworth Group, a division of Thomson...

The Carbohydrates

SugarsStarches

Fiber

Copyright 2005 Wadsworth Group, a division of Thomson LearningCopyright 2005 Wadsworth Group, a division of Thomson Learning


Appendix B

Carbohydrates (CH2O)n

• Simple carbohydrates– Monosaccharides– C6H12O6

• Glucose• Fructose• Galactose

– Disaccharides

• Complex carbohydrates


Glucose


Simplified Diagrams of Glucose

The lines representing some of the bonds and the carbons at thecorners are not shown.

In this and other illustrations throughout this book, glucose isrepresented as a blue hexagon.

Another way to look at glucose is to notice that its six carbonatoms are all connected.

Now the single hydrogens are not shown, but lines still extendupward or downward from the ring to show where they belong.

Fructose & Galactose

Condensation


Hydrolysis


Disaccharides• Maltose• =____________ +____________• Sucrose• =____________ +____________• Lactose• =____________ +____________


Complex Carbohydrates

• Polysaccharides – Animal (Human) Polysaccharide

•Glycogen– Storage product in animals (Made up of

glucose)– Enough storage for less than a day at rest

or few hours of exercise– Synthesized in liver and muscle– Liver glycogen is available to the rest of

the body but muscle tends to use its own glycogen (more in Ch. 7)


• Polysaccharides (Plant)– Starches

•Storage product in plants•Made up of glucose

– Fibers•Provides structure (rigidity) to stems,

roots, leaves etc•Made up of a variety of monosaccharides

and other carbohydrate derivatives

Glycogen & Starch Molecules Compared (small Segments)



• Fibers (Structure)– Cellulose

• Made up of glucose• Different type of bond

– Hemicelluloses• Found in Cereal Fibers• Various monosaccharides

– Pectins• One type of

monosaccharide• Form gels• Used to thicken jelly

(jams)


Link cannot be broken by human digestive enzymes


• Fibers– Gums and mucilages

• Guar Gum, Gum arabic (Gums)• Psyllium, Carrageenan (Mucilages)

– Lignin• Carrots• Seeds of strawberries

– Resistant starches• Whole legumes• Raw potatoes• Unripe bananas



• Fibers– Soluble fibers

•Viscous•Fermentable

– Insoluble fibers•Nonviscous

• (Phytic acid)– Not classed as fiber– Reduces absorption of minerals (e.g. iron in

cereals may not be absorbed well)• Everything you want to know about fibre

– http://www.nlm.nih.gov/medlineplus/dietaryfiber.html– http://www.hsph.harvard.edu/nutritionsource/fiber.html


http://www.nlm.nih.gov/medlineplus/dietaryfiber.html

http://www.nlm.nih.gov/medlineplus/dietaryfiber.html

http://www.hsph.harvard.edu/nutritionsource/fiber.html

http://www.hsph.harvard.edu/nutritionsource/fiber.html

Fiber

• Fiber health benefit– Managing IBS ( normalizes bowel function i.e. keeps you

regular– Shown to lower LDL ("bad") blood cholesterol levels,– Reduce the risk of heart disease,– Minimize colon cancer risks (This has been questioned

recently)– Slow the absorption of fats and carbohydrates into the

bloodstream, which» improves glycemic control » helps prevent the formation of free radicals. » lowers insulin requirements.

• Commercial fiber products– Acacia is gum arabic, Metamucil and Fybogel contain psyllium, Citrucel

contains methylcellulose, Equalactin and Fibercon contains calcium polycarbophil, Benefiber contains guar gum, and FiberChoice contains inulin.


Digestion• Mouth

– Salivary amylase• Stomach

– Fibers and satiety• Small intestine

– Maltase, sucrase, lactase• Pancreas

– Pancreatic amylase• Large intestine

– Fermentation of viscous fibers•Water, gas, short-chain fatty acid

production


Digestion• Available carbohydrates vs.

unavailable carbohydrates (fiber)


Carbohydrate Digestion in the GI Tract


Absorption


Lactose Intolerance• Symptoms

– Bloating, abdominal discomfort, diarrhea• Causes

– Lactase deficiency• Prevalence

– Less among Northern Europeans – More among Native North Americans and

Southeast Asians• Dietary changes

– Does not require the elimination of milk/milk products

– Can use fermented milk products• Yogurt and Acidophilus milk


Glucose in the Body• Energy

• Glycoproteins

• Glycolipids


Carbohydrate Metabolism

• Storing glucose as glycogen

• Using glucose for energy



• Polysaccharides – Animal (Human) Polysaccharide

•Glycogen– Storage product in animals (Made up of

glucose)– Enough storage for less than a day at rest

or few hours of exercise– Synthesized in liver and muscle– Liver glycogen is available to the rest of

the body but muscle tends to use its own glycogen (more in Ch. 7)


• Making glucose from protein– Gluconeogenesis– Protein-sparing action of

carbohydrates



• Making ketone bodies from fat fragments– Ketone bodies

•Ketosis–Acid-base balance



• Converting glucose to fat– Energetically expensive


Constancy of Blood Glucose

• Regulating hormones– Insulin– Glucagon– Epinephrine


Maintaining Blood Glucose

Homeostasis



• Diabetes– Type 1 diabetes

•Failure of insulin production– Type 2 diabetes

•Obesity



• Hypoglycemia– Rare in healthy people



• Glycemic response– Glycemic index


Sugars• Added sugars

– Sucrose, invert sugar, corn syrups, etc.

• Health effects of sugars– Nutrient deficiencies



Sugars

• Health effects of sugars– Dental caries

•Dental plaque


Accusations Against Sugars

• Sugar causes obesity• Sugar causes heart disease• Sugar causes misbehavior in

children and criminal behavior in adults

• DRI– No more than 25% of total

daily energy intake


Accusations Against Sugars

• Sugar causes cravings and addictions– serotonin


Starch and Fiber• Health effects

– Heart disease

– Diabetes– GI health


Starch and Fiber• Health effects

– Cancer– Weight management– Harmful effects of excessive fiber

intake


Viscous Fibers• Soluble and more fermentable• Gums and mucilages• Pectins• Psyllium• Some hemicelluloses


Viscous Fibers• Sources

– Whole-grains, fruits, legumes, seeds and husks, vegetables

– Extracted and used as food additives


Viscous Fibers• Lower blood cholesterol

• Slow glucose absorption

• Slow transit of food through upper GI tract


Viscous Fibers• Holds moisture in stools, softening

them

• Yield small fat molecules that the colon can use for energy


Viscous Fibers• Lower risk of heart disease

• Lower risk of diabetes


Viscous Fibers


Nonviscous Fibers• Insoluble and less fermentable• Cellulose• Lignins• Psyllium• Resistant starch• Many hemicelluloses


Nonviscous Fibers• Sources

– Brown rice, fruits, legumes, seeds, vegetables, wheat bran, whole grains

– Extracted and used as food additives


Nonviscous Fibers• Increase fecal weight

• Speed fecal passage through colon

• Provide bulk and feelings of fullness


Nonviscous Fibers• Alleviate constipation

• Lower risks of diverticulosis, hemorrhoids, appendicitis

• May help with weight management


Nonviscous Fibers


Starch and Fiber• RDA for carbohydrate

– 130 g/day– 45% - 65% total daily energy

intake

• Daily Value: 300 g/day


Starch and Fiber• Fiber

– Daily Value: 25 g/day– AI: 14 g/1000 kcal/day


Guidelines to

Groceries

• Grains


Guidelines to Groceries

• Vegetables

• Fruits



Guidelines to Groceries

• Milk and milk products

• Meats and meat alternatives


Alternatives to Sugar• Artificial sweeteners vs. sugar

replacers (nutritive sweeteners)




Alternatives to Sugar• Saccharine and cancer• Aspartame and PKU


Metabolism of Aspartame

Alternatives to Sugar• Stevia


Alternatives to Sugar• Acceptable Daily Intake (ADI)

• Artificial sweeteners and weight control



Sugar Alternatives on Food Labels

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