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Practical Approach to Adolescent Sports Nutrition
Randon T. Hall, MD, MBA Primary Care Sports Medicine
Division of Pediatric Orthopaedics
Objectives
• Understand the basic physiology of sports nutrition
• Provide practical nutritional recommendations for the competitive athlete in regards to performance
• Discuss commonly used nutritional supplements and ergogenic aids
What do we tell our athletes? “Drink lots of fluids”
“Stay hydrated”
“You’ve got to eat more protein”
“Get some fluids in you”
“Carbo load”
• Examined nutritional knowledge among coaches, ATs, SCS and athletes
• Randomly surveyed NCAA Div I, II, III with 20 question multiple choice questionnaire.
• Weight Management, Hydration, Supplements, Micro and Macronutrient Knowledge
• Also assessed confidence in answers being provided
• 71% of AT’s and 81% of SCS had adequate knowledge of the information (score greater than 75%)
• 9% of Athletes and 35% of coaches had adequate knowledge of information
• Macronutrient and Micronutrients had lowest average score
• Athletes felt most comfortable discussing nutrition information with ATs and SCS
Energy Expenditure
Determinants of Energy Expenditure
Handbook of Sports Medicine and Science, Sports Nutrition
Sport Specific Considerations
• Body Weight and Lean Body Mass
• Sport and Position
• Gender
• Training Regimen (Intensity, Duration, Aerobic vs Anaerobic)
• Caffeine, Tobacco, Climate
Overall Goals
Appropriate Energy Balance
Optimal Sports Performance
Safe Utilization of Ergogenic Aids and Supplements
Energy
ATP
• ATP is required by muscle cells to perform work
• Very little ATP is stored in muscle, so it is not considered a good supplemental energy source.
• ATP stored in muscle would only sustain about 1 second of maximal intensity exercise.
Creatine Phosphate
• Creatine Phosphate (CP) is produced endogenously as well as obtained from the diet.
• ADP + Pi (from CP)= ATP
• CP metabolism is only used for a matter of seconds(~10s). Short bursts (ie. sprints, weights, shot put)
Glycogen
• Glycogen is the storage form of carbohydrate.
• Anerobic Glycogenolysis (ANG) typically starts within 10 seconds and lasts up to 2 to 3 minutes
• ANG - Glycogen is utilized to produce lactate and relatively few ATP.
Glycogen
• Typically after anerobic glycogenolysis is depleted energy from the glucose in blood stream and aerobic glycogenlosysis is utilized.
• As the intensity of exercise increases there is a greater reliance on CHO as energy. When you pass 60-75% V02 max, CHO are primary source of energy.
• Over a period of 1-2 hours muscle glycogen is depleted
and fat oxidation is utilized. (hitting the wall)
Fat
• In low intensity exercise at < 50% of V02 max fat is the primary fuel, accounting for more than 50%
• Additionally, blood glucose and muscle glycogen contribute equally to the remainder of fuel usage.
• Fat oxidation is not adequately sufficient to maintain a running pace and therefore is detrimental in competition.
Macronutrient Utilization
FAT
PRO
CHO
High Intensity V02 Max >65%
FAT
PRO
CHO FAT
PRO
CHO
Low Intensity V02 Max < 50%
FAT
PRO
CHO
Protein • There is no significant store of protein in the body to be
utilized for energy.
• Protein provides 3 to 5 percent of total energy needs during endurance exercise.
• Key to utilizing dietary protein for muscle building is to make sure you have enough muscle glycogen available during exercise!
Prescription
ATP Supplementation
• Not bioavailable, large molecule that is degraded in small intestine
• ATP that is stored in muscle, not considered adequate source of energy
• Even if it was able to be transported to the muscle it would only be useful for a matter of seconds
ATP Supplementation • Arts et al (2012) showed in randomized, placebo controlled
cross over in humans ATP was not bioavailable – Dosage of 5000mg showed no difference in blood levels of ATP.
• Jordan et al (2004) looked at 14 days of ATP (0, 150mg, 225mg) – No significant difference between group treatment effect of any
strength test 75mins, 7 days or 14 days.
– No significant effects for whole blood or plasma ATP
• Coolen et al (2011) evaluated ATP doses of (0, 250mg, 1250mg, 5000mg) for a total of 4 weeks. – No significant effects for whole blood or plasma ATP
ATP Supplementation
$39.95
CP Supplementation
• Small molecule that is easily digested and transported to muscle.
• Harris et al (1992). showed that supplementation can increase muscle creatine levels by up to 20%.
• Rawson et al. (2003) meta analysis, showed individuals ingesting creatine, combined with resistance training, obtain on average +8% and +14% more performance on maximum (1RM) or endurance strength respectively than the placebo groups.
• 7 – 91 days length of supplementation
Proposed Mechanism
• Increased muscle creatine and phosphocreatine prior to exercise will allow for accelerated phosphocreatine re-synthesis, resulting in ability to perform more repetitions of a given exercise before fatigue.
– Increased muscle strength (1 RM)
– Increased training volume
– Increased muscle glycogen storage
– **Increased protein synthesis is still controversial
CP Supplementation
• Metzl et al (2001) reported 44% of 12th graders surveyed reported using creatine.
• Currently AAP does not recommend the use of creatine by young and adolescent athletes.
• To date there has been no evidence to support any significant side effects of creatine use, however no “long term” data is available.
$29.95
Protein
Protein Requirement
• Recommended protein intake for general population is 12-15% of caloric intake
– 2000 calories per day X 13 % = 260 calories
– 260 calories/ 4 calories per gram = 65g of protein
• Non-athletes typically recommended to intake 0.8g per kg of body weight
– 180 lb / 2.2 = 81kg
– 81kg X 0.8 = 65 g of protein
Non - Athlete
Protein Requirement
• Protein requirement for athletes is approximately double that of non-athletes – 1.2 to 1.7 g per kg
– 80kg X 1.5g/kg = 120 g protein
– Remember the protein requirement is not for energy usage during exercise. Generally used for body functions such as enzymatic activity and tissue repair
• Despite the increased protein requirement, most athletes consume enough protein through their daily diet
Protein Requirement
• Typical athlete at 80kg would need 120g of protein
– 4 oz chicken breast = 25 g
– 1.5 cup black beans = 21g
– Jimmy Johns Turkey Club = 44 g
– 2 scrambled eggs = 14 g
– 3 oz can albacore tuna = 21g
• Eat a healthy diet and you should easily take in 1-2g/kg PRO/day
Protein and Muscle
• Two key components to increasing muscle mass – Increased caloric intake of carbohydrate and protein
– Stimulation of muscle enlargement through strength training
• Recommended to increase protein intake 1.5g per kg of body mass desired – 4kg X 1.5g/kg = 6 additional grams of protein
– 4 calories per gram x 6 = 24 kcal
• Recommended to increase carbohydrate intake 30g per kg of body mass desired – 4kg X 30g/kg = 120 additional grams of carbohydrate
– 4 calories per gram x 120 = 480 kcal
Remember Physiology
• A surplus of protein is not particularly beneficial to the body
• Excess protein is broken down to ammonia and converted to urea to be excreted through the urine – Excess water loss
• Excess calories consumed that are not utilized for muscle mass are typically stored as fat – Consuming more calories than necessary, no matter the source, will
lead to weight gain. Just not the kind you want
Carbohydrates
Preparation for Sport
• CHO intake 7-10g/kg per day to replenish stores in 24 hours period.
• Loading - CHO load 10g/kg for 3 days as exercise is tapered. Carbohydrate loading can potentially double the muscle glycogen stored if done correctly.
• 80kg = 176 lbs = 560 - 800g CHO/day
Pre-Game Meal • 3-4 hours prior to game for metabolism
• 1-4 g/kg CHO or about 200 – 300 g CHO
80kg x 3g = 240g CHO
Pre-Game Recommendations
• Aim for 7g/kg CHO per day in active athlete
• Increase to ~10g/kg CHO per day 2-3 days prior to event
• If early morning game, eat right before bed, light snack in AM and continually throughout competition
• Watch large intake too close to game time, may cause insulin spike (rest and digest, decrease blood glucose)
• May consider protein or low GI foods, in addition to CHO just prior to sport to slow absorption to avoid insulin spike.
During Exercise • After 60-120 mins muscle glycogen is depleted
• If sport is greater than 60 mins, continuously replenish CHO throughout
• Absorption is limiting factor so 30-60 g per hour is adequate, (1gm/minute)
Supporting Research
• Below et al. (1995)
– 8 men cycled at 80% of VO2 max for 5Omins
– Followed by performance test to complete a set amount of work as fast as possible
Group Nutrition Performance
1 200 ml water 11.34 min
2 200ml water + 79 g CHO 10.55 min
3 1.3L Water 10.51 min
4 1.3L Water + 79g CHO 9.93 min
In-Game Recommendations
• Plan ahead! If you know length of activity, you can plan accordingly.
• Replenish CHO as you go, every 15-30 minutes.
• Use high GI foods during the game to facilitate absorption
• If tolerated try to consume liquid CHO intake in order to sustain hydration and fuel.
• Don’t over do it. Body can only absorb so much CHO at one time (30-60g).
Post Exercise • “Golden Hour” -Rapid Phase of Glycogen Synthesis (30 - 60 mins)
– No insulin required, GLUT-4 Transporters stimulated by muscle contraction, and low glycogen
– Increased glycogen synthase activity – Increased permeability to muscle cell membrane to glucose
• 2 hours post-exercise there is a 50% reduction in glycogen synthesis
• Goal intake is 1.0 - 1.2g/kg/h -> repeat until meal.
• Should add PRO to this recovery phase as it has a synergistic effect on
insulin release.
Post-Game Recommendations
• Refuel immediately after leaving the field, especially if multiple games in a short period of time. (1g/kg)
• CHO to PRO ratio is usually about 3:1
• High GI foods would be appropriate in this setting.
• Post game meal should be within 2-3 hours after competition, sooner the better.
Recommendations
20 oz = 65g CHO & 20g PRO
Summary
• Understand the physiology, before making recommendations
• Eating a well balanced diet should attain adequate PRO intake.
• CHO, CHO, CHO when focused on performance
• Plan ahead!
• Golden Hour
• Prescribe don’t Generalize
Fluid Intake
• 400-600ml (17-20 oz) fluid at least 4 hours prior to the competition
• If urine is dark an additional 200-400ml 2 hours prior to game time
• Lastly, 200-300 ml 20 mins prior to exercise
• Ideal fluid is a dilute glucose electrolyte solution to replace water loss.
– Water absorption is driven by osmotic gradient so Na+ and Glucose will help with transport.
– Too much glucose will slow intestinal absorption.
Fluid Intake
• Fluid should be replaced at 200-300ml every 20 - 30 minutes – 32oz Gatorade = 1L Fluid and 54g of carbs
• If less than 60-90 minutes water is fluid of choice but if greater a 6-8% carbohydrate solution can enhance performance.
• Basically fluid intake should be about 1.5 times of what is lost. The best way to do this pre and post exercise weights.
Advanced Supplementation
Introduction
In general, the vast majority of healthy athletes of any age DO NOT need nutritional supplementation to a
healthy diet.
Introduction
• Does it need to be supplemented? (is it low?)
• Can it be supplemented? (can we replace it?)
• Is it safe to supplement? (can too much cause harm?)
• Does it alter performance? (does it matter)
• Does it make physiologic sense?
Introduction
Understanding metabolism is the absolute key to understanding nutritional supplementation.
Most supplementation works by taking
advantage of or replicating a know metabolic process in order to augment a certain outcome, such as energy utilization.
Gu’s, Gels, Chews and Bars
• As the intensity of exercise increases there is a greater reliance on CHO as energy. When you pass 60-75% V02 max, CHO are primary source of energy.
• Over a period of 1-2 hours muscle glycogen is depleted and fat oxidation is utilized. (hitting the wall)
• CHO supplementation can help to delay fatigue in exercise
Small Intestine Lumen ↓
Blood Stream ↓
By NuFS, San Jose State University - Own work, GFDL, https://commons.wikimedia.org/w/index.php?curid=3946226
Gu’s, Gels, Chews and Bars
• Based on absorption rate of 1g/min CHO supplements are generally 20 - 30g CHO
• Ideally CHO supplements should have both glucose and fructose to take advantage of multiple channels of absorption
• Also CHO typically should have sodium as glucose is absorbed through a Na+/Glucose symporter
Gu’s, Gels, Chews and Bars
Amino Acid Supplementation
Casein vs Whey Protein
• Quality of protein is based on the amount of nitrogen retained
• Whey protein is easily and rapidly digested
• Casein is more slowly and evenly digested
• Suggested that whey protein can be utilized pre or post exercise and casein utilized in evening and over night
Amino Acid Supplementation
Leucine, Isoleucine, Valine (BCAA)
• BCAA’s are unique in that they can be metabolized in muscle cell, rather than liver
• Potentially used as substrate for energy, which may reduce fatigue
• Can be more readily available for protein synthesis and therefore reduce muscle breakdown
• Lots of BCAA in normal diet and PRO supplements as well
Fat Metabolism
Triacylglycerol (too big)
Pancreatic Lipase
H
H
Monoacylglycerol
2 Free Fatty Acids
Fat Metabolism
• FFA, Monoacylglycerol & Cholesterol combine to form micelles which can be absorbed in SI
• Eventually, if needed for energy FFA can be oxidized in mitochondria of cells.
• Carnitine is needed to shuttle FFA to the mitochondria in order to be utilized for energy
Fat Adaptation
• ↑levels of oral fat intake will ↑FFA to be utilized for energy with less reliance on CHO
• Studies have not shown a benefit to ↑fat prior to exercise > 4 hours
• Studies have not shown a benefit to ↑fat prior to exercise ~ 2 weeks
Fat Related Supplementation
Medium Chain Triglycerides
• Do not require the assistance of mixed micelles for absorption
• Do not require assistance of carnitine to get into mitochondria for oxidation
• In theory MCT’s can potentially help delay fatigue but has not been clearly shown in studies
Carnitine
• Theoretically can improve fat oxidation by improving FFA transport to mitochondria for oxidation
• Unlikely to be effective as supplement because if not deficient (due to metabolic condition) it is not rate limiting step in energy production
Fat Related Supplementation
Caffeine
• Believed to ↑ fatty acid oxidation during exercise
• Can help with mental focus
• 45-60 mins prior to exercise
• Energy gels have 25-50 mg caffeine
• 7-10 day washout period, to get best affect
• Does not appear to have impact on urine out put <300mg
Fat Related Supplementation
Antioxidants
• Reactive oxygen species are a byproduct of aerobic metabolism as oxygen is reduced in the electron transport chain
• ROS can cause cell damage that can impair performance and recovery
• Antioxidants are believed to counteract and neutralize ROS or free radicals, consequently enhancing performance
Antioxidants
Glutathione
• Can neutralize free radicals, however is not well absorbed in small intestine so is not a good oral supplement
Acetylcysteine
• Believed to increase Glutathione levels within the muscle
Antioxidants
Beetroot Juice
• Powerful antioxidant which is high in nitrites that are converted to nitric oxide
• ↑ NO causes vasodilation and increased blood flow and oxygen to muscle
• Believed to reduce oxygen cost of exercise and improve endurance training
Recommendations
• If protein supplementation is necessary consider both whey and casein at strategic times of the day.
• Creatine monohydrate has been shown to be a beneficial supplement with no major short term safety concerns
• MCT’s and BCAA have a physiologic basis for supplementation but have not clearly shown a benefit and can be consumed in one’s diet.
Recommendations
• Caffeine studies have shown a benefit to performance with a good safety profile at low levels
• In general vitamin and mineral supplementation is unnecessary, however MVI’s typically are sufficient in providing “recommended” supplementation.
• Consider supplementation of Vitamin D and Iron as low levels can lead to injury or impact performance
