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Carbohydrates

Carbohydrates. Chapter 5. What are Dietary Carbohydrates?. Organic compounds containing Carbon Oxygen Hydrogen Formed naturally in nature Synthesized ~4 kcal/gram. Types of Carbohydrates. Simple CHO Monosaccharides Glucose (dextrose, grape sugar) Fructose (levulose, fruit sugar)

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Carbohydrates

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  1. Carbohydrates Chapter 5

  2. What are Dietary Carbohydrates? • Organic compounds containing • Carbon • Oxygen • Hydrogen • Formed naturally in nature • Synthesized • ~4 kcal/gram

  3. Types of Carbohydrates • Simple CHO • Monosaccharides • Glucose (dextrose, grape sugar) • Fructose (levulose, fruit sugar) • Galactose (milk sugar) • Disaccharide • Maltose (malt sugar, glucose & glucose) • Lactose (milk sugar, glucose & galactose) • Sucrose (cane or table sugar, glucose & fructose)

  4. CHO Types • Complex CHO • 3 or more glucose molecules • Polysaccharide (3-9 molecules) • Plant starches • Animal starch (glycogen) • or glucose polymer (10 or more molecules) • Maltodextrin • polycose • Fiber

  5. Concentration Units • Mole = gram molecular weight • A mole is the weight in grams of a particular substance, like glucose • Example • Glucose is C6H12O6 • Atomic weight of C is 12, H is 1, O is 16 • Multiply the atomic weight X the number of that element in the molecule and sum it up. - 1 mole glucose is 180 grams

  6. Causes of Muscular Fatigue Related to CHO Use • Muscle Glycogen Depletion • Fatigue begins to occur at approx 30-40 mmole/kg • Short duration high intensity (<60 sec) not affected until glycogen drops below 20 mmole/kg

  7. Causes of Fatigue Continued • Liver Glycogen Depletion • Normoglycemia: 60-100 mg/dl • Hyperglycemia: >140 mg/dl • Hypoglycemia: <45 mg/dl • Decreased levels of BCAA in blood • Reactive Hypoglycemia

  8. Glycemic Index (GI) The GI reflects the rate of digestion and absorption of CHO Blood glucose area after test food GI = X 100 Blood glucose area after reference food

  9. Glycemic Load • Glycemic index relative to the serving size • Some CHO have high GI but are consumed in small quantities per serving • GL = (GI x CHO/serving)/100 • Ratings of glycemic loads • High GL = >20 • Medium GL = 11-19 • Low GL = <11

  10. Use Of GI In Sports Nutrition • Before Exercise: A low-GL CHO should be eaten, particularly before prolonged exercise, to promote sustained CHO availability • During Exercise: Moderate to High-GL CHO foods or drinks are most appropriate • After Exercise: High-GL CHO for glycogen resynthesis

  11. Major Factors Influencing Skeletal Muscle CHO Metabolism During Exercise • Exercise Intensity • Exercise Duration • Training • Diet

  12. Effect of Intensity of Exercise on CHO Utilization

  13. Effect of Exercise Duration on CHO Utilization

  14. Effect of Training on CHO Utilization

  15. Effect of Diet on CHO Utilization

  16. Mixed Diet • Low CHO  High CHO

  17. How Much and What Kind of CHO? • Minimum of100 grams CHO/day necessary for nervous system • For hard training lasting at least 90 minutes per day • 8-10 g/kg of CHO • 2 g/kg PRO • Remainder as fat • Type of CHO varies with timing • High glycemic CHO get on board faster • Low glycemic CHO have sustained effect

  18. Consumption 1-2 hours Before Exercise • Up to 3 g/kg of CHO • 5 mL/kg fluid (2 cups for 75 kg) • Low to moderate glycemic index CHO • Minimal fat and protein

  19. Less Than 1 Hour Before Exercise • Individuals prone to reactive hypoglycemia should avoid CHO, especially high glycemic CHO • May increase glycogen use • 1-2 grams/kg low to moderate GI

  20. 5-10 min Before Exercise • Hypoglycemic response is attenuated • At >50% of VO2max the glycemic response is depressed • Epinephrine is increased which helps maintain blood glucose • 50-60 grams of glucose polymer in 40-50% solution (Gatorlode)

  21. During Exercise • Maximal use of exogenous CHO is ~ 70 grams per hour • Feedings every 15-30 minutes • 5-10% solution of 15-20 grams every 15-20 min • 8 oz of Gatorade contains approx. 15 grams of CHO • Fructose may cause stomach upset • Always test feeding prior to competition

  22. After Exercise • Glycogen resynthesis rate is about 5-7% per hour • 2 hour window following exercise for maximal resynthesis • 1 gram CHO/kg immediately after exercise and every 2 hours for 4-6 hours • High glycemic foods • Combination of CHO and protein is best in a 3:1 ration of CHO to protein.

  23. Alcohol As An Energy Substrate • 7 kcal/gram • By-products of alcohol metabolism released in blood appear to be of little importance to exercising muscle • Alcohol consumed prior to exercise may contribute 5% of energy over 90 min of exercise • Alcohol requires more O2 for metabolism than CHO or fat

  24. Alcohol may interfere with glucose metabolism • Reduced aerobic endurance at 80-85% of VO2max • May reduce rate of gluconeogenesis • Typically represents non-nutritive excess calories contributing to fat storage

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