Carbohydrates

Functions of Carbohydrates Provides energy 4 calories per gram Storage form called glycogen Protein sparing action Normal fat metabolism Fat oxidization in cells produces ketones Ketones- acids that accumulate in blood and urine Ketoacidosis- acid-base balance upset, caused from starvation or low carb diets; can lead to coma or death Provides fiber Creates soft bulky stool that moves quickly through the large intestine

Food Sources Plant foods Good source of vitamins and minerals Cereal grains, vegetables, fruits, sugars Good source of vitamins and minerals Enriched- B vitamins such as thiamine, riboflavin, and niacin added back after processing; also iron Fortified- nutrient added that was never part of the grain, such as folic acid Vegetables Starch- potatoes, beets, peas, lima beans, corn Fiber- green leafy Fruits- fructose Sugars- table sugar, syrup, honey

Classification of Carbohydrates Monosaccharides Disaccharides Polysaccharides

Monosaccharides Glucose- also called dextrose, all other forms converted to this Corn syrup, some fruits and vegetables Only source of fuel for central nervous system, red blood cells, and the brain Fructose- also called levulose Found with glucose in many fruits and honey Sweetest of all monosaccs Galactose- product of the digestion of milk

Disaccharides Sucrose- composed of glucose and fructose Granulated, powdered, brown, and molasses Sweetest, and least expensive Maltose- produced by digestion of starch, created by fermentation process of alcohol Infant formulas, malt beverages, beer Less sweet than glucose or sucrose Lactose- milk sugar Helps body absorb calcium Less sweet than all other sugars

Lactose Intolerance Body unable to digest lactose Insufficient amounts of lactase- enzyme required for digestion of lactose Bloating, abdominal cramps, diarrhea Making cheese: Milk separates into curds (solid) and whey (liquid) Lactose in whey No specific test for lactose intolerance

Polysaccharides Starch- longer to digest; supply energy over a period of time Grains, vegetables, dried beans and peas Parts of the grain: Glycogen- storage form of glucose in the body ½ day’s supply of energy is stored as glycogen Dietary Fiber- called roughage, cannot be broken down by digestive enzymes Soluble: partially dissolves in water Insoluble: does not dissolve in water Cellulose: primary source of dietary fiber Skins of fruits, leaves and stems of vegetables, legumes

Fiber Helps lower blood glucose levels Moves waste materials through colon faster, reducing exposure time to carcinogens Helps prevent constipation, hemorrhoids, and diverticulitis Recommended intake: 20-35 g/day Eating too much fiber in a short period of time can produce discomfort, gas, and diarrhea Choose natural sources rather than supplements

Digestion and Absorption Monosaccharides absorbed from the intestine directly into the bloodstream, carried to the liver, changes to glucose, then carried to cells Disaccharides are converted to glucose Polysaccharides: After cellulose wall is broken down, starch is changed to dextrin, then maltose, then glucose Digestion begins in the mouth where the enzyme salivary amylase changes starch to dextrin. Changes to simple sugars in the small intestine then absorbed by the blood

Metabolism and Elimination Glycogen is formed when the cells cannot hold anymore glucose Stored in the liver and muscles Glucose converted to fat when the body cannot immediately use or store it Glucose metabolism is controlled by insulin When secretion of insulin is impaired or absent, blood glucose levels become high: Hyperglycemia Hypoglycemia: blood glucose levels are low Hunger is mild form and can result in fatigue, shaking, sweating, headache

Dietary Requirements Half of energy should come from carbohydrates, mostly complex carbs About 250 g/day Weight loss and fatigue can result from eating few carbs Surplus of carbs result in weight gain, spoiled appetite, and tooth decay

Fats

Functions of Fat Energy Cushion to protect organs Insulation Transports vitamins 9 calories per gram 30% of daily calories

Sources Animal foods Cooking oils (from plants) Nuts avocados

Classification of Fats Saturated- animal foods Monounsaturated- olive oil, peanut oil, nuts, avocados Polyunsaturated- soybeans

Cholesterol Found in animal foods Can lead to heart attacks LDL- bad cholesterol HDL- carry cholesterol away from the heart and back to the liver

Protein

Function of Proteins Energy Build and repair body tissues Help maintain fluid and electrolyte balance 4 calories per gram 10% of daily calories

Sources Complete proteins- animal foods Incomplete proteins- plant foods Soybeans are complete proteins Complementing proteins- combination of incomplete and complete proteins