Carbohydrates

What are Carbohydrates?• CHO make up 3% of the body’s organic matter

• CHO are compounds constructed in a ratio of one atom of carbon and two atoms of hydrogen for each oxygen atom

• Chemical Formula = (CH2O)n– Where n is from 3 to 7 carbon atoms– 5 carbon sugars are called pentoses– 6 carbon sugars are called hexoses (most common)

Carbohydrate2 Hydrogen for each Oxygen

Glucose - C6H12O6

Categories of Carbohydrates

• Monosaccharides (glucose, fructose, galactose

• Disaccharides (sucrose, maltose, lactose)

• Polysaccharides (starch, fiber, glycogen)

Monosaccharides•Glucose•Fructose•Galactose

Dissaccarides• Combination of 2 or more monosaccharides

– Mono + Disaccharides = SIMPLE SUGARS

Sucrose = glucose + fructose (brown sugar;

25% of sugar intake)

Lactose = glucose + galactose (milk

sugar; least sweet)

Maltose = glucose + glucose (honey)

Natural Sweetness

Is Refined Sugar a Villain?• To much sugar results in eating less of

something else - Sugar Causes Malnutrition• Eating sugar without eating less of something

else, results in enough nutrients but too many kCal - Sugar Causes Obesity

• Excess sugar converts to fat and so causes hyperlipidemia - Sugar Causes High Levels of Blood fat and Atherosclerosis

• Concentrated sugar is not natural and dangerous• Sugar causes diabetes• Sugar causes tooth decay

Polysaccharides3 or more simple sugars combined

Plant PolysaccharidesStarchpeas, seeds, corn, gains, cereals, potatoes, roots

Cellulosefiber (technically not a nutrient)

Polysaccharides• Animal Polysaccharides - GLYCOGEN

– Ranges in size from a few hundred to thousands of glucose molecules linked together like sausage links

– 375-475 g stored in body (liver, muscle, kidney)

– Can be modified by diet and exercise

Animal Polysaccharides• Glycogen

– Large molecules– Stored in liver (100 g) and muscle (325 g)– Because little glycogen is stored - it can be

modified by diet and exercise– Why do we want to conserve muscle glycogen?

• Glucose intake during exercise 70g/140 H2O, 20-30 min prior to exercise

CHO Conversions• GLYCOGENESIS = Glycogen

derived from glucose

• Glycogenolysis = In liver, glucose derived from glycogen

• Gluconeogenesis = In liver, glucose derived from protein (non CHO products)

Dietary Fiber• Water insoluble fibers [cellulose, hemicellulose, lignins,

pectins, gums, wheat bran]• Water soluble fiber [oats, beans, rice, peas, carrots, fruits]

• Health Implications of Fiber [obesity, diabetes, intestinal disorders, cancer, cholesterol effects]

• Recommended intake of fiber [ 20-30 g/d]– Americans eat about 12 g/d– Africans eat about 40-150 g/d

Guess who has the highest incidence of colorectal cancer?

Not All CHO The SameThe Glycemic Index

GI = a relative measure of the extent to which blood glucose increases after ingesting 50 g of CHO.

Functions of CHO• Energy Source

• Protein Sparing

• Metabolic Primer

• CNS Fuel

Sources of CHO

What Happens when you Consume CHO?

Blood Glucose

Liver Glycogen

Adipose Tissue

Used for Energy

Muscle Glycogen

Kidney Excretion

[Type, duration, intensity]

Hypoglycemia v HyperglycemiaHypoglycemia - low

blood sugar; hormones (glucagon) stimulate liver to release sugar into blood

Hyperglycemia - high blood sugar; insulin aids sugar uptake from blood to cells; with excess blood sugar, spills out to kidneys and is urinated out (sweet urine).

Sensitivity v underproduction

CHO and Endurance Exercise