Military “Sports” Nutrition Patricia A. Deuster, PhD, MPHProfessor and DirectorHuman Performance Laboratory
Objectives • List 3 key sports nutrition goals • Describe issues for hydration status • Discuss issues relating to CHO and protein intake after exercise • List 4 characteristics of the ideal fluid replacement beverage • Identify 2 current sports nutrition issues
Key Nutrition and Performance Goals • Optimize/maintain hydration/ electrolyte status • Maximize/maintain fuel supplies • Maximize protein synthesis to increase lean body mass • Accelerate recovery from a strenuous bout of activity
Human Water Needs • Water is quintessential nutrient of life: • 50-70% of body weight is water • 75% of lean body/skeletal muscle mass is water • Intra- and Extra-cellular fluid compartments • Intra ~ 65% and Extra ~ 35% or TBW • ~ 5 - 10% of TBW is turned over each day. • NRC recommends fluid intakess approximating 1 mL/kcal of energy expended.
Functions of Water • Important functions of water • Makes up plasma, which transports and delivers nutrients to tissues • Maintains body temperature and pH • Maintains blood circulation and pressure • Supports energy processes
Regulation of Water Balance • Thirst • Daily water balance varies between 0.2 and 0.5% each day, independent of climate • Metabolism • Daily turnover between 3.3 and 4.5 L/day (6 L for very active populations) for sedentary and active populations • Requirements • Low activity: 4.5 - 8 L/day • High Activity: 6 to 12 L/day • Losses • 1 - 2 L/h for athletes
Dehydration and Performance 8 6 4 Weight Loss (% Body Weight) 2 2% 3% 4 - 6% > 6% Impaired temperature regulation Reduced muscular endurance Reduced strengthReduced endurance capacityHeat cramps Severe heat cramps Heat strokeComaDeath
12 3 4 5 6 7 8 9 Monitoring HydrationStatus Urine color test for dehydration Lemonade—The good Apple juice—The bad Tea—The ugly
Establishing Fluid Needs • Estimate sweat rate or amount of fluid lost in a specified period of time during defined exercise workload • A: Body weight: Pre - Post • B: Fluid intake: Total volume • C: Urine volume • Sweat loss = A + B - C • Sweat rate = Sweat loss/time
Example of Fluid Needs • Body weight • Before = 70 kg and after = 67 kg • Fluid intake = 1.8 L • Urine volume = 0.7 L • Time = 2 hours or 120 min. • Sweat loss = (3 + 1.8 - 0.7) = 4.1 • Sweat rate = 4.1 L/2 hrs = 2.05 L/hr
Hydration Guidelines for Pre-Exercise • Obtain body weight. • Check color of urine - pale color (1 - 3) indicates a good hydration status. • Drink 16 to 20 fl oz of water or sports beverage 2 to 3 hrs before. • Drink 8 to 12 fl oz of water 0 to 10 min before exercise.
Hydration Guidelines for During Exercise • Drink 3-8 fl oz of water every 15-20 min when exercising for < 60 min • Drink 3-8 fl oz of a beverage with CHO (5% to 8%) and electrolytes every 15-20 min when exercising> 60 min. • DO NOT DRINK MORE THAN 1 L or 1 Qt/hr during exercise.
Hydration Guidelines for Post-Exercise • Obtain body weight to estimate fluid losses and correct losses within 2 hrs. • Rehydration is optimized when a volume equivalent to 150% of the body weight deficit is ingested. • Beverage should contain water to restore hydration status, CHOs to replenish glycogen stores, and electrolytes to accelerate rehydration.
US Track & Field Guidelines Guidelines: 3/19/2003 http://www.usatf.org/coaches/library/hydration/ International Marathon Medical Directors Association (IMMDA) Advisory Statement on Guidelines for Fluid Replacement During Marathon Running, by Tim Noakes, MBChB, MD, FACSM Fluids on Race Day, by LG Maharam, MD, FACSM Proper Hydration for Distance Running - Identifying Individual Fluid Needs, by DJ Casa, PhD, ATC, FACSM
Institute of Medicine • Most healthy people meet hydration needs by letting thirst guide fluid intake. • Healthy sedentary people in temperate climates: 91 oz (2.7 L) of water per day for women and 125 oz (3.7 L) per day for men from all dietary sources. • Very active people continually exposed to hot weather have daily total water needs of 6 L or more. Panel on Dietary Reference Intakes for Electrolytes and Water, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes 2004.
ACSM Position • Thirst is not the best hydration indicator for active people and those who are exposed to heat • Athletes should replace fluids in amounts that approximate sweat losses.
Hyponatremia • A post-race blood study on 481 participants who ran the 2002 Boston Marathon found that 13% experienced hyponatremia. • Risk factors included female gender, slower finishing times, and excess fluid consumption.
12 3 4 5 6 7 8 9 Summary: Hydration Status • Fluid intake should match fluid losses. • Urine should be monitored: • Pre-exercise urine should be < 3 • If urine color > 6 thendehydration is likely. • Dehydration is NOT acceptable, whether involuntary or voluntary. • Dehydration is NOT an unconditional outcome of exercise, or combat/military operations. • Hyponatremia is avoidable.
Optimal Fluid Replacement Beverages • Rapid rate of gastric emptying; • Tastes good; • Provides energy substrate, if exercise > 1 hr; • Rate of energy delivery is adequate (40 - 90 g/L or 36 - 76/qt); • Provides requisite amount of sodium (0.5 to 0.7 g/L): Need to replace body fluids > need to replace electrolytes; • Absence of GI disturbances; • Best if beverages are cool (10 to 15°C).
Volume of Solution Caloric Density Osmolarity Temperature pH Increases with larger volumes Decreases with greater density Decreases with hyperosmolar solutions Faster for cool solutions Slower with more acidic solutions Gastric Emptying and Solution Characteristics Solution Characteristic Rate of Emptying
Gastric Emptying • Slow at high exercise intensities; • Same at rest and low to moderate exercise intensities; • Affected by fitness—the more fit, the less affected by exercise; • May be enhanced by training; • Not affected by exercise duration; • Affected differently by various activities.
Minimize GI Distress During Exercise • Maintain hydration - hypovolemia increases frequency of GI complaints; • Avoid high-energy, hypertonic drinks and foods before (30 - 60 min) and during exercise (< 90 g/hour); • Avoid high fiber foods before exercise; • Limit NSAIDs, caffeine, alcohol, and dietary supplements before and during exercise.
Maximize Glycogen Synthesis • Glycogen - primary fuel source during moderate to high intensity exercise • Muscle glycogen repletion is slow, and can take 24 hrs. • Exponential relation between rate of glycogen resynthesis and recovery time • Restoration of muscle glycogen most critical factor for recovery/ subsequent performance
Factors Affecting Glycogen Resynthesis • Depletion of muscle stores • Refueling pattern - timing of ingestion • Amount of carbohydrates consumed • 1.0 to 1.2 g CHO/kg BW immediately after • 1.0 to 1.2 g CHO/kg every 30 min for 5 hrs • 6 - 10g CHO/kg BW per 24 hours • Type of carbohydrate consumed • Focus on high glycemic index/GIfoods post-workout
Effects of Diet on Muscle Glycogen Content 140 120 100 High CHO 80 Low CHO 60 Muscle Glycogen (mM/kg wet wt) 40 20 0 Day 1 Day 2 Day 3 Day 4 Time
Glycogen and Endurance Exercise: CHO vs Protein? • Glycogen can be restored rapidly if 1.2 g/kg/hr of CHO are ingested immediately after and for up to 4 hours after exercise. van Hall G et al. J Appl Physiol. 2000;88:1631-6. • Does ingestion of CHO and AA in combination improve glycogen repletion?
Muscle Glycogen Resynthesis Rate Muscle Glycogen (nmol/kg) Recovery Time (hr) van Hall G et al. J Appl Physiol. 2000.
Glycogen and Resistance Training: CHO • Resistance exercise reduces glycogen by approximately 30-40%; • Resynthesis is slow unless energy substrates are provided; • Provision of CHO after exercise enhances resynthesis of glycogen; • Provision of protein and fat with CHO after exercise does not impair resynthesis.
Low CHO diet (40% kcal from CHO) Double cheeseburger Medium fries Chocolate milkshake High CHO diet (70% kcal from CHO) 12 inch sub sandwich (lots of vegetables & no mayo) 500 ml apple juice 250 ml chocolate milk banana Comparison of Diets
Carbohydrate Snacks • Foods supplying 50g CHO • 500 ml Juice • 3 Medium pieces of fruit • 1 honey sandwich • 2 breakfast bars • 1 sports bar (check label) • 1.3 bagels • 1/2 cup dried fruit • 1 cup white rice • 1 baked potato
Maximize Protein Synthesis • Resistance exercise stimulates muscle protein synthesis and degradation. • Net protein balance negativein absence of nutrient intake. • Timing of pre- and post-exercise nutrient intake may affect rate of protein synthesis.
Protein Balance and Resistance Exercise • Ingestion of 40 g of essential amino acids (AA) resulted in positive muscle protein balance after resistance effort. Tipton KD et al. Am J Physiol. 1999;276:E628-34. • Ingestion of 6 g of essential AA combined with 35 g of CHOs at 1 and 3 hr post-exercise increased muscle protein balance.Rasmussen BB et al. J Appl Physiol. 2000;88:386-92.
Protein Balance and Resistance Exercise • Ingestion of CHO and AA together was equivalent to the sum of giving either alone in terms of enhancing muscle protein balance. Miller S et al. Med Sci Sports Exerc. 2003;35:449–55. • Ingestion of CHOs alone minimally improved net muscle protein balance after resistance exercise relative to placebo. Borsheim E et al. J Appl Physiol. 2004;96:674-8.
Typical Amino Acid Profile • 6 g of essential AA in amounts designed to raise free intracellular amino acid pool to levels reflecting requirements for protein synthesis: • Amounts in mg/L:Histidine: 1.3 Isoleucine: 1.2Leucine: 2.24 Lysine: 1.86Methionine: 0.38 Phenylalanine: 1.86 Threonine: 1.76 Valine: 1.4
Glycemic Index and Insulin Response Index • Glycemic Index (GI): Ranking of food based on blood glucose response to reference food. • High GI (dextrose and maltose): Evoke large increases in glucose. • Carrots, raisins, corn flakes, breads, rice cakes • Low/Moderate GI (sucrose and lactose): Evoke small/modest increases in glucose. • i.e.. Yogurt, apples, dried fruit, lentils, beans • Insulin Response Index (IRI): Ranking of food based on blood insulin response to same reference food.
GI > 85 White Bagel English Muffins Doughnut Raisins Corn Chips Ice Cream Sports Drinks GI < 60 Yogurt Grapefruit/Oranges Beans Peanuts Apples/Pears/Plums Milk Brown Rice Glycemic Index of Foods http://www.glycemicindex.com/
CHO to Protein Ratio • Pre- and Post-Exercise: 3, 5, or 4 to 1 • Cognitive Performance: Wide range in literature 1 to 1 or 4 to 0 • Weight Loss: 1.4 to 1
Recovery Nutrition • Provision of CHO, protein and fat to marine recruits immediately post exercise during basic training decreased muscle soreness and total medical visits associated with heat exhaustion, muscle/joint problems, and infections as compared to providing placebo (no energy) Flakoll et al. JAP 2004;96:951-956.
Critical Re-Fueling Interval Re-FuelingInterval Re-FuelingInterval Recovery Recovery Exercise Exercise Phases of Timing Nutrient Intake
Optimizing Protein Metabolism • Slow and fast dietary proteins • Structure affects rate of absorption • Absorption affects metabolic response • Fast protein: Whey • Soluble • Slow protein: Casein • Clots in stomach
Fast vs. Slow Proteins • Fast proteins increase blood AA rapidly and stimulate protein synthesis and oxidation • Slow proteins promote post-prandial protein deposition by inhibiting breakdown • Fast protein might be more beneficial during aging and wasting.
Omega 6 Fatty Acids (Linoleic Acid) Omega 3 Fatty Acids (Alpha-Linolenic Acid: ALA) Δ6-Desaturase Gamma-linolenic acid (GLA) Evening Primrose Oil Borage Oil Black Current Oil Eicosapentaenoic Acid (EPA) COX Δ5-Desaturase Lipoxygenase Arachidonic Acid Prostaglandins PGE1, PGE3 (Favorable) Less Inflammatory Leukotrienes Cyclo-oxygenase (COX) Lipoxygenase Docosahexaenoic Acid (DHA) Prostaglandins (PGE2) Inflammatory Leukotrienes