Carbohydrates

Body’s preferred energy source Human brain uses it exclusively 2 categories

• simple• complex

Found in plants and dairy products

Carbohydrates

Simple sugars• monosaccharides• disaccharides• sweet

Complex sugars• polysaccharides• not sweet

Glucose

Fructose

Galactose

Found only as part of lactose

Sucrose

Lactose

Maltose

Absorbed directly into blood stream without digestion Glucose (plant sugar) - 4 kcal/g

• from starch digestion or hydrolysis Other forms of CHO are converted

into glucose - needs insulin for take up Dextrose- monohydrate of glucose

• used in IVF (3.4 kcal/g)

Fructose- fruit and honey Sweetest of all sugars Used almost exclusively in soft drinks Can be used in very small amounts

to hide after taste in diet drinks

Galactose Appears in nature only as part of

lactose “milk sugar” Changed to glucose for energy Reaction is reversible During lactation glucose

reconverted to galactose for use in milk production

Compounds used in medications Cardiac glycosides - digitalis Steroids Antibiotics - streptomycin,

erythromycin Deoxy sugars - DNA

Derivatives- sugar ETOH Sorbitol side effects: diarrhea, gas,

abdominal discomfort Helps with dental caries Sorbitol occurs naturally in prunes,

apple juice, etc. Liquid medications

Glucose

Fructose

Galactose

Found only as part of lactose

Sucrose

Lactose

Maltose

Maltose = glucose and glucose Plant sugar found in germinating cereal grains Used in some infant formulas and

cereals Highly significant in human

nutrition as intermediate product of starch digestion

Pairs of simple sugars linked together Sucrose = glucose and fructose Sugar beets, sugarcane, molasses,

maple syrup Fructose converts to glucose in body 7-11% total kcal in American diet NO difference between honey and sugar

Lactose=glucose and galactose Principle CHO of milk Lactose intolerance common

-no lactase or digestive enzyme in digestive system-can be transient after illness

Starch, glycogen, dextrin, dietary fiber

Starch- hundreds of linked glucose units

Amylopectin and amylose-ratios and structures differ

~80-85% amylopectin- insoluble ~15-20% amylose-soluble

Amlyopectin- thickening agent Amylose - slow even rate of

digestion Amylase-digestive enzyme Cereal grains, legumes, potatoes Dextrin-intermediate product from

breakdown of starch-makes maltose

Glycogen

Stored energy Found in liver and muscle

tissue Important link in energy

metabolism Sustains normal blood sugars

during fasting

Oligosaccharides

Small portions of partially digested starches (3-10 monosaccharides)

Infant formulas Special dietary formulas Sports drinks Faster and easier to digest

Dietary fiber

Soluble and insoluble Celluloses, pectins, mucilages,

gums, lignin Need 20-35 grams/day Have laxative effect, soften

stools Increase transit time, influence

blood lipid levels

Dietary fiber

Increase satiety Bulk helps with weight control,

constipation, diverticulosis Undesirable effects-

binds Fe++, Ca++, & Zn++

Produce colon bacteria-volatile short chained fatty acids/GAS

Insoluble-Cellulose & Lignin

Cellulose-not digestible• has no nutrients• produces bulk • grains, fruits, vegetables

Lignin is non-carbohydrate fiber• binds bile acids and metals• whole grain, strawberries, mature

vegetables

Insoluble

Soften stools Regulates bowel movements Increase fecal weight Increase transit time Reduce risks of diverticulosis,

hemorrhoids, and appendicitis

Non-cellulose fiber

Soluble-Absorbs water Slows gastric emptying Binds bile acids Adds some bulk Found in

• pectin• gums • mucilage

Carbohydrate Digestion

Polysaccharides are broken down to

Disaccharides are broken down to

Monosacharides which are absorbed through intestinal mucosa and transported to the liver

Carbohydrate Metabolism

In the liver:• Fructose and Galactose converted to

Glucose Blood sugars rise Insulin secreted Insulin moves glucose out to bloodstream and into cells

Carbohydrate Metabolism

Muscle cells convert glucose to glycogen if storage CHO is needed.

IF energy needed, glucose is burned in cells.

Glucose not needed for energy or glycogen is used to make DNA, RNA, or converted to fatty acids and stored as triglycerides.

Carbohydrate Function

Provides energy-especially to brain, nervous system, used by muscles

4 kcalories per gram Spares protein Prevents ketosis Quickly digested-principle site is

small intestine

Glycogen

Immediate fuel for muscle actions 1200-1500 kcal on board 2/3 stored in muscle/ 1/3 in liver 2.7- 3.4 g of water stored with

every gram of glycogen

Glycogen

Minimum of 100g CHO/ day to prime citric acid cycle

to prevent keto-acidosisto prevent excessive tissue

protein breakdown Symptoms from lack of CHO :

fatigue, dehydration

Healthy Diet

CHO 50-60% of daily diet 10% of this amount should be

sweets Fiber intake 20-35 grams/day CHO alone does not cause obesity

• remember fat and activity levels

Chronic Diseases

Diabetes-Type 2 related to body fatness• 95% of DM are Type 2

Heart Disease-fat not sugars

Sugar behavior-unproven

Nutrients in 100 Kcalories

Food Protein Calcium Sugar (2T) 0 g trace Cola (1 C) 0 g 6 mg Milk (1 c) 8 g 300 mg Bread ( 1 slice) 3 g 48 mg Pinto Beans (1/2 c)

7 g 41 mg

Sugar Alcohols

Used in chewing gums 2-3 kcal per gram Examples:

• Sorbitol• Isomalt• Xylitol

Artificial Sweeteners

Saccharin-pros and cons Aspartame-Equal Acesulfame K- Sunette & Sweet

One Sucralose-Splenda Use as replacement, not addition,

if used for weight control

Glycemic Response

Effect of a particular food on blood glucose reduced to a number

Factors:• Amount of fat and fiber• Method of preparation• Amount eaten

Use for fine tuning meal planning with DM patients and athletes

GI Food Pyramid

Refined Grains Potatoes Sweets

Unrefined Grains Pasta

Dairy Lean Protein Nuts Legumes

Fruits Vegetables

Fat & Energy

Used to meet 50% of energy needs• Most cells can utilize fat for energy

• Not brain cells or nerves

Fat cannot be converted to glucose

Ketosis?

Ketone bodies• Acidic, fat related

compounds formed from incomplete breakdown of fat when no carbohydrate is available.

Protein and Energy

Protein used for energy when• glycogen depleted• Body starts to auto-digest

CHO has protein sparing effect