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
 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
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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
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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