Presentation on theme: "Carbohydrates in Exercise and Recovery"— Presentation transcript:
1 Carbohydrates in Exercise and Recovery Rookie version
2 Outline I. Carbohydrates: Definitions, digestion, absorption A. Carbohydrates in the dietB. Digestion and absorption of carbohydratesC. Carbohydrate metabolismD. Glycogen—storage of carbohydrates in the bodyII. Properties of carbohydrates: Considerations for sports performanceA. Glycemic indexB. Glycemic load C. High-fructose corn syrupIII. TrainingA. Carbohydrates before exerciseB. Carbohydrates during exerciseC. RecoveryD. Meal planningIV. CompetitionA. Carbohydrate loadingB. Pre-competition mealsC. Carbohydrates during competition
3 Definitions, Digestion, Absorption, and Storage I. Carbohydrates:Definitions, Digestion, Absorption, and Storage
4 Carbohydrates in Sports Nutrition Carbohydrates (CHOs) are a major fuel source for exercising muscle, especially in high-intensity or long-duration activitiesCarbohydrates can influence fluid absorption from the intestine (hydration)Some CHOs can cause gastrointestinal intolerance and thereby impair exercise performanceTypes of CHOsExogenous: CHO intake from the dietEndogenous: CHO stored in the body (ie, glycogen) that can be used for energy needsGlycogen is stored glucose in the bodyIt is a network of glucose molecules connected together, similar to starchUnited States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, 2011.
5 Carbohydrates in Diet Carbohydrates are found in the diet as 1. Free monosaccharides (1 sugar unit)Glucose (aka dextrose, from corn and other plants)Fructose (from fruit)Galactose (from milk)2. Di-, tri-, oligo- (4 to 10 units), or polysaccharides (chain of 11+ monosaccharides)Sucrose (disaccharide of glucose + fructose)Lactose (disaccharide of glucose + galactose)Maltose (disaccharide of 2 glucose molecules)Trehalose (disaccharide of 2 glucose molecules, with a different linkage between the two)Starch (polysaccharide of glucose)Add picturesBerg JM, et al. Biochemistry. 5th ed. New York, NY: WH Freeman and Co; 2002.
6 Carbohydrate Digestion Carbohydrates are absorbed as monosaccharidesEnzymes must digest di-, tri-, oligo-, and polysaccharides into individual monosaccharidesEnzymes exist in the saliva, stomach, and small intestine to break the different linkages between the various sugarsThere are special transporters in the cell membranes of intestinal cells that selectively absorb monosaccharidesMonosaccharides are then transported into the blood stream, where they are distributed throughout the bodyCarbohydrates that escape digestion and absorption make their way to the colon (with variable degrees of bacterial fermentation)Holmes R. J Clin Pathol. 1971;5(suppl):10-13.
7 Why Is Carbohydrate Absorption Important in Sports Nutrition? The ability of the intestine to absorb a carbohydrate can be the rate-limiting step for its delivery to muscle cells for fuel useEnzyme systems in the intestine may be insufficient to digest some carbohydrates (eg, lactose intolerance)Intestinal sugar transporters can become saturated, resulting in malabsorption of a carbohydrateThere are multiple transporters for carbohydratesIngest a blend of sugars that require different intestinal transporter systems (ie, glucose and fructose)Avoids saturation of any one transporterMay increase carbohydrate absorption relative to using just a single sugar
8 Carbohydrate Metabolism Electron transportchainGlucoseCO2Pyruvate oxidationKrebs cycle (aka tricarboxylic acid or TCA cycle)ATP energyGalactoseFructoseGlycolysisGlycogenintermediateBerg JM, et al. Biochemistry .5th ed. New York, NY: WH Freeman and Co.; 2002.
9 Storage of Carbohydrate in the Body If glucose is absorbed, but not needed right away, the body stores a small amount as glycogenGlycogen is a fluctuating storage pool for glucoseThe structure of glycogen is similar to starchFound in the liver and skeletal musclesGlycogen in liver is a reserve glucose supply to the brainGlycogen in muscles is an energy source for exerciseBerg JM, et al. Biochemistry .5th ed. New York, NY: WH Freeman and Co.; 2002.
10 Glycogen During Exercise During exercise, glycogen is broken down and glucose molecules enter glycolysis (ie, energy metabolism)Vitamin B6 is a structural part of the enzyme that breaks down glycogenShows one of the many roles of B-vitamins in energy metabolismGlycogen can supply the body with only a limited amount of energyExogenous carbohydrates are important for high-intensity and long-duration exerciseEat carbohydrates immediately after exercise for most rapid glycogen replenishment (recovery)Ingestion of 50 grams of carbohydrate every 2 hours can result in up to 5% glycogen replacement per hourTherefore, total replacement would take 20 hoursHui YH. Handbook of Food Science, Technology, and Engineering. Volume 1. Boca Raton, FL: CRC Press; 2006: United States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, Tardie G. The Sports Journal. Available at: Accessed February 17, 2011.
11 II. Properties of Carbohydrates: Considerations for Sports Performance
12 Glycemic Response to Carbohydrates in Sports Nutrition Ingestion of carbohydrates affects both blood glucose levels and insulin response (glycemic response)1Can influence energy sources during exerciseOne measure of glycemic response is the glycemic index (GI)2,3Glycemic load is a relatively new measure for glycemic response4Based on the concept that exercise performance may be determined by both carbohydrate ingestion and the glycemic response of the overall diet1. Mondazzi L and Arcelli E. J Am Coll Nutr. 2009;28:455S-463S. 2. Burke LM, et al. Int J Sport Nutr. 1998;8: Donaldson CM, et al. Int J Sport Nutr Exerc Metab. 2010;20: O’Reilly J, et al. Sports Med. 2010;40:27-39.
13 What Is the Glycemic Index? System of ranking foods according to how much they raise blood glucose relative to a reference foodDeveloped by Jenkins DJ, et al. Am J Clin Nutr. 1981;34(3):Rapidly digested or absorbed carbohydrates = high GISlowly digested or absorbed carbohydrates = low GIReferences on GIBrand-Miller J, et al. The New Glucose Revolution. 3rd ed. New York, NY: Marlowe & Co.; 2006Written by experts on GIAtkinson, et al. Diabetes Care ;31(12):Most comprehensive table of the glycemic index of foods that has been assembled to dateAtkinson, F. S., Foster-Powell, K., & Brand-Miller, J. C. (2008). International tables of glycemic index and glycemic load values: Diabetes Care, 31(12),Brand-Miller et al. The New Glucose Revolution: The Authoritative Guide to the Glycemic Index-The Dietary Solution for Lifelong Health. 3rd ed. New York, NY: Marlowe and Company; 2006Abbreviations: GI, glycemic index. Figure from
14 What Does the Glycemic Index Value Mean? The glycemic index (GI) is expressed as a ratio comparing the blood glucose increase caused by a test food to that of a reference food (usually glucose, historically white bread) for 2 hours following ingestion:GI values:Split peas = 25 ± 6Golden delicious apples = 39 ± 3Oatmeal = 51 ± 8Raisin bran flake type of cereal = 61 ± 5White bread = 75 ± 2Long-grain white rice = 76 ± 7Corn flake type of cereal = 81 ± 3Area Under the Curve for Test FoodArea Under the Curve for Reference Food× 100= GIAtkinson FS, et al. Diabetes Care. 2008;31(12):
15 Slow and Fully Digested CHOs (Low GI) Isomaltulose1Glucose and fructoseMore steady and sustained release of glucose into the blood compared with sucroseOccurs naturally in honey, but can be synthesized from sucroseSucromalt2Produced by enzymatic conversion of sucrose and maltose into a fructose and oligosaccharide syrup~40% fructose, ~50% oligosaccharides, and ~10% other mono- and disaccharidesDigestion profile similar to isomaltuloseGamma-cyclodextrin (γ-CD)3Ring of 8 glucose molecules+Abbreviations: CHO, carbohydrate; GI, glycemic index. 1. Lina BA, et al. Food Chem Toxicol. 2002;40(10): Xtend™ Sucromalt. Cargill, Inc. Available at: Accessed February 24, Munro IC, et al. Regul Toxicol Pharmacol. 2004;39:S3-13.
16 What Is the Glycemic Load? Takes into account the amount of carbohydrate in a common serving in addition to its glycemic indexExampleCarrots (peeled, boiled) have a GI of 47 and 5 g CHO per servingGL = (GI of CHO × gram CHO per serving) ÷ 100The GL of carrots is: (47 × 5) ÷ 100 = 2.4Abbreviations: CHO, carbohydrate; GL, glycemic load; GI, glycemic index.Atkinson FS, et al. Diabetes Care. 2008;31(12):
17 Glycemic Index and Load Standards for Foods GI (based on glucose reference)Low GIIntermediate GIHigh GI ≥ 70GLLow GLIntermediate GLHigh GL ≥ 20Abbreviations: GI, glycemic index; GL, glycemic load.Brand-Miller J, et al. The New Glucose Revolution: The Authoritative Guide to the Glycemic Index-The Dietary Solution for Lifelong Health. 3rd ed. New York, NY: Marlowe and Co.; 2006.Brand-Miller JC, et al. Am J Clin Nutr. 2003;77(4):
18 Limitations of glycemic index approach before and during exercise Clinical data have been mixed regarding the effectiveness of the glycemic index (GI) in food choice before exerciseSome discrepancies associated with how researchers evaluate exercise performanceBenefits observed in some time to exhaustion studiesMainly no benefits in studies of time trial performanceNo adverse effects of low glycemic index foods on performance have been observedCarbohydrate ingestion during exercise can help maintain blood glucose and eliminate the need for low glycemic index pre-exercise foodLow glycemic index pre-exercise foods, though, may help reduce insulin response (may positively affect fat utilization during exercise)If an athlete has inadequate access to carbohydrate during an event, low glycemic index carbohydrates before event may be helpfulSome of the low glycemic index foods used in research studies (e.g., lentils) might not be palatable as pre-exercise foods for athletesBurke LM, et al. Int J Sport Nutr. 1998;8: Donaldson CM, et al. Int J Sport Nutr Exerc Metab. 2010;20:
19 What Is High-Fructose Corn Syrup? Cornstarch is converted to corn syrup that is essentially 100% glucoseEnzymes and processing techniques convert some of the glucose to fructose to achieve corn syrup that is 55% fructose (HFCS-55)HFCS-55 is the type of corn syrup used mainly in the beverage industrySyrup is 55% fructose, 45% glucoseSimilar to sucrose (table sugar; 50% fructose, 50% glucose)The term “high-fructose corn syrup” is a little misleadingBecause corn syrup is 100% glucose, any presence of fructose typically results in it being labeled “high-fructose corn syrup”Soenen S, et al. Am J Clin Nutr. 2007;86(6): Smith JS, et al. Food Processing: Principles and Applications. Ames, IA: Blackwell Publishing; 2004:
20 The Truth About High-Fructose Corn Syrup Too much sugar, of any kind, in beverages is not recommendedIt is easy to consume too much energy, leading to weight gainMost sugar-sweetened beverages provide little to no vitamins, minerals, or other essential nutrientsHowever, there are no differences in metabolic responses to high-fructose corn syrup vs sucrose in humansNo differences in circulating hormonesNo differences in appetite or satiety-related variables (fullness)DiMeglio DP, et al. Int J Obesity. 2000;24:Melanson KJ, et al. Nutrition. 2007;23(2):Stanhope KL, et al. Am J Clin Nutr. 2008;87(5):Soenen S, et al. Am J Clin Nutr. 2007;86(6):
22 Carbohydrates and Sports Nutrition Important for maximizing muscle glycogen storesDepleted muscle glycogen—“Hitting the wall”Depleted liver glycogen—“Bonking”Both phenomena are experienced as a precipitous loss of energy as a result of low blood sugarTraining and high carbohydrate diets maximize glycogen storesUnited States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, 2011.Ensminger A. Foods and Nutrition Encyclopedia 2nd Edition Volume 1. Boca Raton, FL: CRC Press LLC; PagesBurke L. Practical Sports Nutrition. Champaign, IL: Human Kinetics; Page 124.Clark N. Sports Nutrition Guidebook 4th Edition. Champaign, IL: Human Kinetics; Page 119.
23 Carbohydrate and Fat Use at Different Exercise Intensities As the intensity of exercise increases, muscle glycogen constitutes a greater portion of the energy source(Weightlifting, sprinting, etc)300(Soccer, dancing, etc)Muscle glycogen200Muscle triglycerideEnergy Expended, cal/kg/minPlasma FFA(Leisurely walking, slow cycling)100Plasma glucose256585Maximal Oxygen Consumption, %Abbreviations FFA, free fatty acid. Romijn JA, et al. Am J Physiol. 1993;265(Part 1):E380-E391.
24 Carbohydrates in the Days Before Exercise High glycogen stores are very important to prolong enduranceRelated to diet and exercise in the days and hours before exercising/competingEndogenous carbohydrate oxidation occurs at high intensityEspecially important for events longer than minutes (eg, marathons and cycling events)United States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, 2011.Latta S. Marathon & Beyond. 2003;7(5).
25 Carbohydrates 1 to 2 Hours Before Exercise Low glycemic index foods and beveragesEspecially important for endurance exerciseCarbohydrates that are also low in fiber may be beneficial due to varied gastrointestinal sensitivity among individualsExamplesFruit juicesBagelsBreakfast cereals with < 3 g fiber/servingPotatoesCarbohydrate amounts vary among individuals, sport type, and sport intensityUnited States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, 2011.Wu CL and Williams C. Int J Sport Nutr Exerc Metab. 2006;16(5):
26 Carbohydrates During Exercise Are Also Important Jeukendrup (2004) reviewed multiple studies (n = 22) of walking, running, and cycling in which carbohydrates were given during exercise23 of 36 observations within these studies showed a positive effect of carbohydrate on enduranceEffective doseMinimum, 16 to 22 g carbohydrate/hourMaximum, 75 g carbohydrate/hourNo studies showed an adverse, or ergolytic, effect of carbohydrate on performanceForm of carbohydrate (solid or liquid) was of little significance, although the vast majority of the studies used a beverageSports beverages that include different types of sugars will be absorbed via different sugar transporters in the gutIncrease exogenous carbohydrate oxidation during exercise from 1.0 g/min to 1.2 to 1.5 g/minJeukendrup AE. Nutrition. 2004;20(7-8):
27 Carbohydrates After Exercise Carbohydrates that are quickly digested and absorbed are recommended postexercise to restore muscle glycogen levels as fast as possibleGlucoseMaltoseMaltodextrinProtein + carbohydrates postexercise maximizes the rate of glycogen synthesisWhen intervals between exercise sessions are < 8 hours, consume carbohydrates as soon as practical postexercise for fastest recoveryIvy JL, et al. J Appl Physiol. 2002;93:
28 Recommendations for Carbohydrate Intake During Recovery Carbohydrate intakes are expressed per kga not % of energyFor immediate recovery after exercise (0 to 4 hours)1.2 g/kg/hr consumed at frequent intervalsFor daily recovery, range of 3-12 g/kg/day; adjust with consideration of:Athlete’s total energy needsSpecific training needs and stage of trainingFeedback from training performanceTraining intensity3-5 g/kg/day: very light training programs (low-intensity or skill-based exercise)5-7 g/kg/day: moderate intensity training programs for 60 min/day6-10 g/kg/day: moderate- to high-intensity endurance exercise for 1-3 hours per day8-12 g/kg/day: moderate- to high-intensity exercise for 4-5 hours/dayaMultiply the numbers by 0.45 to get carbohydrate intake in grams per pound of body weight.Burke LM, et al. J Sport Sci. 2004;22(1):15-30.
29 Putting Together a Meal Plan Example:70-kg athlete requiring 4000 kcal/day and exercising 120 min/day 4 to 6 times/weekMacronutrient Target RecommendationsGrams/kg (body weight)/dayCarbohydrate 7 to 10 g/kg/day (490 to 700 g/day)Protein 1.5 to 2.0 g/kg/day (105 to 140 g/day)Fat Typically use percentage of energy as methodPercentage of energyFat 20% to 35% of energy (88 to 156 g/day)Target recommendations for this athleteCarbohydrate 600 g (60% of energy)Protein 130 g (13% of energy)Fat 120 g (27% of energy)
30 A Potential Distribution of Macronutrients Over the Course of 6 Meals/Day TimeCarbohydrate, gProtein, gFat, gBreakfast7:00 am9015Mid-AM snack10:00 am25105LunchNoon7520Pre-Ex meal1:30 - 2:00 pmDuring Ex3:00 - 5:00 pm100Post-Ex meal5:00 pm30Dinner6:30 pm12035PM snack9:00 pmTOTALS600130
31 Foods Containing Approximately 25 to 30 g Carbohydrate 1 cup of juice or 1 large piece of fruit1 bagel or 2 slices of bread1 cup of most cereals1 large baked potato2 cups of milk⅔ cup of dried beans1 cup of rice or corn1 cup of squash (other non-starchy vegetables have less carbohydrate)2 cups of commercial sports/electrolyte replacement drink½ to 1 energy bar (1 bar 25 to 45 g carbohydrate)1 pack of energy gel ( 25 g carbohydrate)Atkinson FS, et al. Diabetes Care. 2009;31(12):
32 Examples of Postexercise Meals Option 11 regular bagel2 Tablespoons peanut butter8 fl oz skim milk1 medium bananaMeal provides 562 kcal, 77 g carbohydrate, 23 g protein, and 18 g fatOption 217-oz commercial nutrition shakeProvides 300 to 420 kcal, 17 to 70 g carbohydrate, 32 to 42 g protein, and 2 to 16 g fat
34 CompetitionCompetitions sometime require different carbohydrate intakes than practiceEndurance may be required for a longer amount of timeMaximum glycogen levels are optimal for best performance and require time to build (on the order of days; not possible for practices)Do not try any new foods in competition before you try it at least once at practice
35 Carbohydrates as Energy at Different Times Carbohydrate consumed in the days before eventUsed to provide adequate glycogen stores in musclePrevent “hitting the wall”Carbohydrate consumed in the hours before the eventUsed to preserve liver glycogen stores, which can deplete after approximately 8 to 12 hours of fastingCarbohydrate consumed during eventUsed to maintain blood glucose, especially when liver glycogen is depletedCarbohydrate in the hours before and during exercise helps to prevent “bonking”United States Anti-doping Agency. Optimal dietary intake guide. Available at: Accessed January 31, 2011.Ensminger A. Foods and Nutrition Encyclopedia 2nd Edition Volume 1. Boca Raton, FL: CRC Press LLC; PagesBurke L. Practical Sports Nutrition. Champaign, IL: Human Kinetics; Page 124.Clark N. Sports Nutrition Guidebook 4th Edition. Champaign, IL: Human Kinetics; Page 119.
36 Carbohydrate Loading Traditional protocol Cons Depletion of glycogen stores (~ days 6 to 3 before event)Low-carbohydrate diet and hard exerciseSupercompensation of muscle glycogen (during the 36 to 48 h prior to event)Very high-carbohydrate diet (10 to 12 g/kg body weight/day) and tapering of exerciseConsDepletion phase is hard on the body and difficult to tolerate in trainingMay lead to headaches, irritability, and increased risk of injury
37 Pre-Competition MealOne of the most variable aspects of the athlete’s dietDepends on individual toleranceAthletes often have certain beliefs about food’s effect on performanceRanges from no food to the old “steak and eggs” breakfastDepends on the sport to some degreeFunctions of the pre-event mealPrevent dehydrationMaintain adequate muscle and liver glycogen levelsAvoid excess hunger feelingsConfidence in preparation for the event
38 Pre-Competition Meal (continued) Medium amount of energy300 to 500 kilocalories, more if there is time to digest before the event2 to 3 hours before event (perhaps 1 hour with liquid meal)Ingestion of carbohydrate 1 hour before exercise does not usually impair performanceDepends on individual toleranceLiquid meals are popular for gastrointestinal comfort during the eventGI of pre-event carbohydratesNo solid evidence for this, experiment in practiceInclude 1 to 2 cups of fluidAvoid foods with a high fat content and/or excess fiberAbbreviations: GI, glycemic index.
39 Examples of Pre-Competition Meals Option 1, liquid meal (blend all ingredients)11 cup of vanilla yogurt4 to 6 peach halves, canned or fresh4 graham cracker squaresDash nutmeg, optionalMeal provides 450 kcal, 75% CHO, 15% protein, and 10% fatOption 2FoodKcalCarbohydrate, gProtein, gFat, gOatmeal, instant 1 pkt1041842Skim milk, ½ cup436Toast, 2 slices14624Banana, 1 medium105271Orange juice, 6 oz8420TOTAL48295 (80%)13 (11%)5 (9%)Abbreviations: CHO, carbohydrate; pkt, packet.1. Clark N. Sports Nutrition Guidebook. Champaign, IL: Human Kinetics; 1989.
40 Carbohydrates During Competition Consuming carbohydrate is neither practical nor necessary during exercise lasting less than 45 minutesSmall amounts of carbohydrate from sports drinks or foods may enhance performance during sustained high-intensity exercise lasting minutesAthletes should consume g carbohydrate per hour from carbohydrate-rich fluids or foods during endurance and intermittent, high-intensity exercise lasting hoursDuring endurance and ultra-endurance exercise lasting hours and beyond, athetes should consume upt to g carbohydrate per hourProducts providing multiple transportable carbohydrates are necessary to achieve these high rates of carbohydrate oxidationJeukendrup AE. Nutrition. 2004;20(7-8): Burke LM, et al. Carbohydrates for training and competition. J Sport Sci (in press as of April 2011).
41 Summary of Key Messages A diet with high carbohydrate availability helps to maximize glycogen stores and generally increases exercise performanceConsuming carbohydrate during exercise also generally helps performanceExperiment in practice regarding tolerated levelsLiquid carbohydrates also help with hydrationEating as soon as possible after exercise promotes the most rapid recovery of muscle glycogenCombination of carbohydrate and protein may facilitate this processFrequent, smaller meals can help athletes with high energy and carbohydrate requirements get in the required amounts of nutrients