II. Physiology: Nutrient Requirements
- Water is the most important nutrient for the athlete
-
Carbohydrates (bulk of calorie intake for sports)
- Athlete requires 5-10 grams/kg/day
- Carbohydrates comprise 65-70% of daily calories
- Protein
- Fats comprise 15-20% of an athletes total calories
III. Management: High Carbohydrate diet
- Maximizes intensity and endurance of Exercise
- Maintains Muscle glycogen
- Added to fluids for faster absorption
- Increase Carbohydrate before Exercise (70% of calories)
- Start increase the day before
- Consume up to 2-5 hours before competition
- Liquid Carbohydrate may be taken 60 minutes before
- Benefit appears to be regardless of Glycemic Index
- Avoid Reactive Hypoglycemia from Insulin surge
- Avoid Carbohydrates within 60 minutes of Exercise
- Highest Hypoglycemia risk with high Glycemic Foods
- Glucose
- Sucrose
- Maltodextrin
- Low Glycemic Foods may not result in Insulin surge
- During endurance competitive event
- Consider Carbohydrate intake during endurance event
- Several studies show performance benefit
- Solid Carbohydrates may be equivalent to liquid
- Maintaining adequate hydration is paramount
- After competitive event
- Drink or eat 50 gram high glycemic Carbohydrate ASAP
- Repeat high Glycemic Foods every 2 hours
- Take in over 100 grams Carbohydrate in 4 hours
- Take in over 600 grams Carbohydrate in 24 hours
- Start simple, liquid high Glycemic Food and advance
IV. Management: Vitamins and Minerals
- Multivitamin used by up to 80% of athletes
- Supplementation results in no performance improvement
- Supplementation may be beneficial in specific cases
- Iron and Calcium may be deficient in women
- Vitamin B12 may be deficient in strict Vegetarians
V. Management: Water
- Precautions
- Overhydration (and associated Hyponatremia) is as problematic as underhydration
- Stay hydrated
- Drink 1 quart non-caffeinated fluid per 1000 calories
-
Preload fluid 10-30 minutes before competition
- Drink 250 to 1000 ml of liquid
- During Exercise
- Drink 4-8 ounces (150 to 250 ml) every 15 minutes
- Current recommendations are to drink to thirst to avoid overhydration and Hyponatremia
- Some recommend limit of 800 ml per hour
- Drink cool water
- Temperature for maximal water absorption: 40 F
- Add 5-8% Carbohydrates if Exercise >45 minutes
- Carbohydrate intake totals 30 to 75 grams per hour
- Sports Drinks also contain Electrolytes and can reduce Hyponatremia risk
- However, most sport drinks are hypotonic and carry Hyponatremia risk with overhydration
- Drink 4-8 ounces (150 to 250 ml) every 15 minutes
- Post event
- Replace each pound of weight loss with 480 ml (16 oz)
- Replace half fluid losses in first 4 hours
- Replace half fluid losses in next 8 hours
VI. Example: Foods for athletes
-
Calcium sources
- Low-fat milk or yogurt
- Fruits and vegetables
- Bananas
- Oranges
- Broccoli
- Apricots
- Cantaloupe
- Carrots
- Green pepper
- Kiwi
- Strawberries
- Sweet potato
- Winter squash
-
Carbohydrates
- Potatoes
- Whole grain breads, bagels or crackers
- Fortified cereal
- Pasta with tomato sauce
- Thick crust Vegetarian pizza (low fat cheese)
-
Protein sources
- Extra-lean roast beef
- Fish
- Tuna with no mayonnaise or low-fat mayonnaise
- Salmon
- Black Beans, Kidney beans or navy beans
- Lentils
- Tofu
VII. References
- Clark (1994) Physician Sportsmed 22(5):60-3
- Dimeff (1997) AAFP Sports Medicine, Dallas
- Kleiner (1997) Physician SportsMed 25(10):123-4
- Ahrendt (2001) Am Fam Physician 63(5):913-22 [PubMed]
- Lemon (1992) J Appl Physiol 73:767-75 [PubMed]
- Tarnopolsky (1992) J Appl Physiol 73:1986-95 [PubMed]