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Key Concepts◦ provide practical energy (calorie) sources

availability relatively low cost storage capacity

◦ structures vary from simple to complex provide both quick and extended energy for the body

◦ Dietary fiber and indigestible CHO serves separately as a body regulatory agent

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Identify ◦the nature of carbohydrates◦the functions of carbohydrates◦food sources of carbohydrates◦digestion of carbohydrates◦the body’s need for carbohydrates

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Photosynthesis Process chlorophyll-containing plants manufacture

carbohydrate by combining CO 2 from air and water from soil (with sunlight used as energy)

Saccharide Chemical name for sugar molecule

Simple carbohydrate Sugars with a simple structure of one or two

single sugar units

Complex carbohydrate Large complex molecules of carbohydrates

composed of many sugar units

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Sugar Alcohols: sorbitol, mannitol and xylitol

Sorbitol: formed in mammals from glucose and converted to fructose

Enzymes (proteins) digest or change specific nutrients in specific chemical reactions with out being changed themselves in the process

Brush Border – Cells located on the microvilli within the lining of the intestinal tract

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Energy: - necessary for life- Require basic fuel supply

Basic fuel source-Sugars and starches: main sources of energy for

the body-The body breaks down these stores of quick

energy and sustaining energy sources provide the major source of energy in the form of calories

NOTE: “Energy” is used interchangeably with calorie or kilocalorie

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Must do the following:-Change the basic fuel to a refined fuel that the

machine is designed to use

-Carry this refined fuel to the places that need it

-Burn this refined fuel in the special equipment set up at these places

The body easily does these 3 things

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The body digests basic fuel: CHO◦changing it to glucose◦absorbs the glucose◦through the blood circulation, carries this refined fuel to the cells that need glucose

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Carbohydrates are widely available and easily grown – grains, legumes, vegetables and fruits

Carbohydrate are relatively low in cost

Carbohydrates are easily stored

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Carbohydrates are made up of carbon (C), hydrogen (H), and oxygen (O)

Saccharide is used as a carbohydrate class name, the word comes from the Latin word meaning ‘sugar’ [saccharum]

A saccharide unit = a single sugar unit

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CHO are classified according to the number of sugar or saccharide units:

Monosaccharides- one sugar unit; a simple sugar or simple carbohydrate- building block for all carbohydrates, requires no further digestion: corn syrup

Disaccharides – two-sugar units; simple sugars or simple carbohydrates; table sugar, sugar cane, molasses, milk, starch digestion

Polysaccharides- Complex carbohydrate has large complex compound of many polysaccharides units in long chains; grains, cereal, bread, crackers, rice, cord, legumes, potatoes, liver, muscle meats, animal tissue

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3 single sugars in nutrition are:◦Glucose◦Fructose◦Galactose

They are quickly absorbed from the circulation intestine liver

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Glucose- Basic single sugar in body metabolism; the form of sugar circulating in the blood; primary fuel for cells

Fructose- Found in fruits or in honey. Sweetest of the simple sugars- amount of sugar in fruit depends on its ripeness

Galactose- Comes from digestion of milk sugar or lactose

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Sucrose: glucose and fructose combined;made from sugar cane or sugar beets

E.g. table sugar, powdered, brown sugar

Lactose: Sugar found in milk = glucose and galactose combined; lactose stays in body longer and creates formation of useful bacteria. Cows milk is 4.8 % lactose as human milk is 7 % lactose

Maltose: derived from intermediate digestive break down of starch. Synthetically derived maltose is used as a sweetener in processed foods

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Starch-Most significant polysaccharide in the diet. Found in grains, legumes and other vegetables. Break down slowly. Supply energy over a period of time.

- 45%-65 % of total kcal are from starch.

Whole grain – Food products such as flour, bread, and cereals that still retain its outer bran layer and the inner germ endosperm and nutrients

Glycogen – formed in body tissues and found in liver and muscles where it is constantly recycled. Stored form of carbohydrate and is stored in liver

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Dietary fiber: - Humans lack the enzymes to digest dietary fiber. Consequently, there is no direct energy value like other CHO.-An important dietary asset related to GI

problems, CV disease, and management of DM

-Can be divided into 2 groups: soluble, insoluble

See both: p.17 Box 2-1; p.18 Table 2-2

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Cellulose: ◦ Mostly from plants. Undigested in the GI tract

and provides bulk to the diet. Main source is stems and leaves of vegetables. Not soluble in water.

Lignin: ◦ Woody part of plants. Binds with bile acids and

cholesterol to prevent their absorption. Not soluble in water

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Noncellulose polysaccharides:Hemicelluloses, pectins, gum and mucilages:

They all absorb water and swell to a larger bulk -> slowing the emptying of the food mass from the stomach, binding bile acids (including cholesterol) in the intestine, preventing spastic colon pressure by providing bulk for normal muscle action

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Sugar Alcohols and alternative sweeteners are often used as sugar replacement:

- Nutritive sweeteners: Sorbitol, mannitol xylitol are the alcohol form of sucrose;

2-3 kcals/g CHO

- Nonnutritive sweeteners- aspartame and saccharin

no kcals

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In review:Basic fuel supply- 4 Kcal/gFuel for the bodyBurn in the body (at 4kcal/g CHO) to meet energy

needs

Special tissue functionsLiver – Glycogen reserves in the liver and muscle

– create reserves to protect cells form depressed metabolic function and resulting in injury

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Review cont: Regulate protein and fat production-

Proteins are broken down for source of energy if no carbohydrates available. CHO has a protein-sparing action in the body.

Fat may be used for energy also. However, when incomplete breakdown of fat occurs –> Ketones (are the by product and are strong acids -> create acidosis). This can upset the acid- base balance.

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Heart – Fatty acids are the preferred fuel for the heart muscle. Glycogen is used in emergency situations- may cause cardiac disorder and angina

Central Nervous System –the brain has no stored supply of glucose; its dependent on a minute-by-minute supply of glucose from the blood. Shock from low blood sugar may cause brain damage - > death

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Starches – fundamental complex carbohydrate foods for slowly available glucose

Sugars- not necessarily the villain in the story of health

Problem = too much sugar, often to the exclusion of other important foods

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1. Some starch is broken down by salivary amylase to maltose.

2. Salivary amylase is inactivated by strong acid

3. Enzymes (amylase) from pancreas break down starch into maltose

4. Enzymes in wall of small intestine break down diasaccharides sucrose, lactose and maltose into monosaccharides- glucose, fructose, and galactose

5. Absorption of glucose, fructose and galactose into blood stream to be taken to the liver

6. Some soluble fiber is fermented into various acid and gases by bacteria in the large intestines

7. Insoluble fiber is excreted in feces, but little other dietary carbohydrate is present.

Digestion: Mechanical and Chemical

Mechanical - the process of chewing the food: mastication

Chemical – specific enzymes breakdown the food into smaller usable metabolic products.

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Mouth – mixes food with saliva and salivary amylase (ptyalin) secreted by the parotid gland, located under ear and in back of jaw

Stomach- peristalsis: wave-like action of muscles fibers of the stomach wall.

Gastric secretions contain no specific enzyme for the breakdown of CHO

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Hydrochloric acid in the stomach stops the action of the salivary amylase in the food mass

Small intestine – carbohydrate digestion is complete in the small intestines by enzymes secreted by the pancreas

Pancreatic secretions are pancreatic amylase which breaks down disaccharides and monosaccharides

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Intestinal secretions- sucrase, lactase, and maltase- they act on their respective disaccharide to glucose, galactose and fructose ready for absorption directly into the portal blood circulation

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Dietary Reference Intakes (DRIs)

-In the nutrient standards, energy needs are listed as total kcalories (kilocalories)

45 % - 65 % (225 TO 325 g) of an adult’s total caloric intake should come from carbohydrates for a 2000 kcal diet

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Dietary Guidelines for AmericansGeneral guidelines to promote health

Not specific in terms of caloric consumption or where those kcalories should come from

However, they do advise individuals to:Choose fiber-rich fruits, vegetable, whole

grain oftenChose and prepare food and beverages

with little added sugars or caloric sweeteners

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MyPlate : www.choosemyplate.gov◦Tips for consuming more whole grains,

fruit, vegetables◦Serving size information◦Health benefits and nutrients associated

with each food group◦Sample menus

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Lactose Intolerance: ◦Results from a lack of the enzyme

lactase◦S/S- bloating, gas, abdominal pain,

diarrhea

African American and Native American suffer from lactose intolerance more than Caucasian

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80%-100% of Native Americans and Asian

Americans endure some form of lactose intolerance

~ 80 % of African American suffer with some form of lactose intolerance

2 % - 15% of Northern European descendants suffer from lactose intolerance

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