© 2006 Thomson-Wadsworth The Carbohydrates Sugars Starches Fiber

© 2006 Thomson-Wadsworth

The Carbohydrates

SugarsStarches

Fiber



Carbohydrates (CH2O)n

• Simple carbohydrates–Monosaccharides–Disaccharides

• Complex carbohydrates


Simple Carbohydrates

• Monosaccharides

– C6H12O6

•Glucose•Fructose•Galactose


Glucose


Fructose & Galactose


Condensation


Hydrolysis


Disaccharides

• Maltose

• Sucrose

• Lactose


Complex Carbohydrates

• Polysaccharides– Glycogen– Starches– Fibers




• Fibers– Cellulose– Hemicelluloses– Pectins



• Fibers– Gums and mucilages– Lignin– Resistant starches



• Fibers– Soluble fibers

•Viscous•Fermentable



• Fibers– Insoluble fibers

•Nonviscous

• (Phytic acid)


Digestion

• Mouth– Salivary amylase

• Stomach– Fibers and satiety


Digestion

• Small intestine– Maltase, sucrase, lactase

• Pancreas– Pancreatic amylase


Digestion

• Available carbohydrates vs. unavailable carbohydrates



Digestion

• Large intestine– Fermentation of viscous fibers

•Water, gas, short-chain fatty acid production



Absorption


Lactose Intolerance

• Symptoms

• Causes– Lactase deficiency


Lactose Intolerance

• Prevalence

• Dietary changes– Does not require the elimination of

milk/milk products– Acidophilus milk


Carbohydrate Metabolism

• Storing glucose as glycogen

• Using glucose for energy



• 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




• Diabetes– Type 1 diabetes

•Failure of insulin production– Type 2 diabetes

•Obesity



• Hypoglycemia– Rare in healthy people


Constancy of Blood Glucose• Glycemic response

– Glycemic index


Sugars

• Added sugars– Sucrose, invert sugar, corn syrups,

etc.


Sugars

• Health effects of sugars– Nutrient

deficiencies


Sugars

• Health effects of sugars– Dental caries

•Dental plaque


Recommended Intakes of Sugars

• DRI– No more than 25% of total daily

energy intake


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


Documents

© 2006 Thomson-Wadsworth The Carbohydrates Sugars Starches Fiber