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Nutrition for Sports Performance

Kathleee Stewart wrote the following fantastic article on how best to optimize your sports performance through proper nutrition.

Nutrition for Sports Performance
Fueling the machine (that’s you!)

Most of us grew-up familiar with the USDA’s food guide pyramid. Remember that grains and carbohydrates lived at the base of the pyramid and were supposed to make up the majority of our meals. The second level was a combination of “fruits and vegetables” and above that was “dairy and protein”. The tip of the pyramid (I know you remember this one) was “fats and sweets” and was supposed to make-up the smallest amount of your daily caloric intake. Well, times have changed. The USDA now uses a tool dubbed “My Plate” and is a more easily applied version of the pyramid. “My Plate” is a pictorial description of what your actual dinner (or lunch or breakfast) plate should look like. Protein and fruits should each comprise less than a quarter of the plate whereas grains and vegetables should each make-up just over a quarter of the plate. Dairy comes as a side or drink. My Plate also provides ten basic tips to help you enjoy a more balanced and healthful diet. This advice includes: balance calories, avoid large portions, drink fat-free or low fat (1%) milk, make half of your grains whole grains, watch out for sodium, drink water instead of sugary drinks, cut back on foods high in solid fats, added sugars and salt, and eat more fruits, vegetables, whole grains, and low fat dairy. Although these guidelines are a great platform for the general public, there are many other aspects to consider when designing a diet for a competitive athlete. The rest of this article will outline the basic principles of nutrition and athletic performance.
Today, it is widely accepted that optimal nutrition positively affects physical activity, athletic performance, and recovery from strenuous exercise and/or competition. Although much research has been done in this area, the definitive borders of “optimal nutrition” remain a little blurry.
Why is nutrition important to the competitive athlete?
Athletes need to consume high amounts of energy in order to replenish what is lost in the body during training and competition. Also, a lack of adequate energy intake can result in muscle breakdown, decreased bone density, menstrual cycle dysfunction (leading to further health risks), an increase risk of fatigue, injury, or illness, and prolonged recovery from injury or illness.
So what should my daily intake look like?
Compared to the general public a competitive athlete needs to consume more fluids, to make-up for those lost primarily by sweating, and consume more energy, to restock depleted stores. Food and fluid requirements vary depending on energy needs of the sport (i.e. endurance sports like long-distance running versus spring sports like ice hockey), the athlete (sex and age), duration of the competition, as well as the overall palatability and gastrointestinal (GI) compatibility of the diet to the athlete. In general, the athlete should consume 6 - 10 grams (g) of carbohydrate per kilogram (kg) of body weight (2.7 – 4.5 g/pound of body weight). Dietary carbohydrates are used to replace the energy lost in the liver and muscle and to restore blood-glucose levels. Athletes who participate in strength or endurance competitions should consume 0.5 – 0.8 g of protein per pound (lb) of body weight. Strength athletes require more protein than other types of athletes because of the requirements for muscle growth and building, which demands dietary protein. Endurance athletes require more protein because their body breaks down body proteins, like muscle, during extended exercise when carbohydrate sources run out. Other athletes can consume at, or slightly above, the Recommended Dietary Allowance (RDA- set by the U.S. federal government) (0.8g/kg body weight, 10 - 35% of total dietary calories). Fat intake in athletes should represent 20 - 35% of the total daily caloric intake. Saturated, polyunsaturated, and monounsaturated fat should each comprise ten percent of the total daily fat intake.
When is it most beneficial to eat?
Timing is everything. Before competition it is very important to eat a meal or snack that is easy on the gastrointestinal tract (low fat and fiber), relatively high in carbohydrate, and moderate in protein. This meal must be well tolerated by the athlete and should be made of familiar foods. Ideally, consume 200 - 300g of carbohydrate 3 - 4 hours before training. Some athletes may be able to tolerate this meal closer to competition but this may not allow for adequate nutrient absorption by the body. On the other hand, some athletes may need to eat earlier because of gastric issues.
During long duration competition (> 1hr) it is important to consume 30 – 60 g of carbohydrate per hour, especially in extreme heat, cold, or high altitude environments. During these longer competitions it is best to ingest carbohydrate every 15 - 20 minutes rather than a larger bolus every hour. This strategy aids in digestion, absorption, and delivery of the energy.
After a competition, 0.5 - 0.7g of carbohydrate per pound of body weight should be consumed. This should be repeated every two hours for 4 - 6 hours post competition. Consuming carbohydrate within the first 30 minutes post-exercise provides quicker repletion of energy stores than if eating is delayed until two hours post-exercise. Adding protein may help restore protein levels and aid in muscle repair but it is not a necessary factor in energy store repletion. This regimen of carbohydrate repletion is unnecessary if there is greater than one day off between training sessions as that provides ample time for energy stocks to replete.
What about fluids?
Euhydration is a termed used to describe the normal state of hydration. Research has shown the importance of euhydration. A loss of 2 - 3% of your body weight during competition or training has been shown to decrease performance, especially in aerobic sports (i.e. soccer) and decrease mental and cognitive functioning. Also, the consequences of dehydration may be lethal. Therefore, it is imperative to drink adequate fluids before, during, and after competition.
The level of euhydration disturbance during exercise depends on the type, intensity, and duration of the exercise as well as on the environment (heat, cold, and high altitude environments tend to increase dehydration). Hydration status of the athlete before exercise also has an impact on the level of dehydration during exercise.
When is it most beneficial to drink?
Research states that four hours pre-competition an athlete should drink 5 - 7 ml/kg. Consuming more than this may lead to the urge to void during the competition and has shown no added benefit to performance. Consuming less than this amount may lead to a state of hypohydration, which puts the athlete at an added risk for dehydration during the competition.
During competition, the amount of fluid consumption varies depending on the individual athlete’s sweating capacity, as well as the intensity, duration, and type of exercise and the environment in which it is performed. Fluid replacement with sports drinks is encouraged. The added carbohydrate will aid in glucose replacement. Further, the electrolytes (sodium and potassium) in those drinks will aid in fluid retention. A 6 - 8% carbohydrate drink is optimal.
After competition, drink 16 - 24 ounces of fluid per pound of body weight lost. This too can be comprised of carbohydrate drinks.
Also, note that all athletes are different and, just like for food, there are differences in tolerability.

References
American Dietetic Association, Dieticians of Canada, American College of Sports Medicine. American College of Sports Medicine position stand. Nutrition and athletic performance. Medicine and Science in Sports and Exercise. 2009;41(3):709-31. http://www.acsm-msse.org

Goldstein et al. International society of sports nutrition position stand: caffeine and performance. Journal of the International Society of Sports Nutrition. 2010;7:5 http://www.jissn.com/content/7/1/5

http://www.choosemyplate.gov/ Last .Modified: July 12, 2011 10:24 AM. Retrieved July 28, 2011.

Kiens B, Ivy JL, Burke LM. Carbohydates and fat for training and recovery. Journal of Sports Sciences. 2004;22(1):15-6.