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)

Carbohydrate 2 Hydrogen for each Oxygen

Glucose - C 6 H 12 O 6

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

Polysaccharides 3 or more simple sugars combined Plant Polysaccharides Starch peas, seeds, corn, gains, cereals, potatoes, roots Cellulose fiber (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 – 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 H 2 O, 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 [ g/d] –Americans eat about 12 g/d –Africans eat about g/d Guess who has the highest incidence of colorectal cancer?

Not All CHO The Same The 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 Hyperglycemia Hypoglycemia - 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