The following key points summarize the current energy, nutrient, and fluid recommendations of the American Dietetic Association and the American College of Sports Medicine for active adults and competitive athletes. These general recommendations can be adjusted by sports nutrition experts to accommodate the unique concerns of individual athletes regarding health, sports, nutrient needs, food preferences, body weight and body composition goals.
Athletes need to consume adequate energy during periods of high-intensity and/or long-duration training to maintain body weight and health and maximize training effects. Low energy intakes can result in loss of muscle mass, menstrual dysfunction, loss of or failure to gain bone density, an increased risk of fatigue, injury, and illness and a prolonged recovery process.
Body weight and composition should not be the sole criterion for participation in sports; daily weigh-ins are discouraged. Optimal body fat levels depend upon the sex, age, and heredity of the athlete, and may be sport-specific. Body fat assessment techniques have inherent variability and limitations. Preferably, weight loss/fat loss should take place during the off-season or begin before the competitive season and involve a qualified sports dietitian.
Carbohydrate recommendations for athletes range from 6 to 10 g/kg (2.7to 4.5 g/lb) body weight per day. Carbohydrates maintain blood glucose levels during exercise and replace muscle glycogen. The amount required depends upon the athlete's total daily energy expenditure, type of sport, gender and environmental conditions.
Protein recommendations for endurance and strength-trained athletes range from 1.2 to 1.7 g/kg (0.5 to 0.8 g/lb) body weight per day. These recommended protein intakes can generally be met through diet alone, without the use of protein or amino acid supplements. Energy intake sufficient to maintain body weight is necessary for optimal protein use and performance.
Fat intake should range from 20% to 35% of total energy intake. Consuming 20% of energy from fat does not benefit performance. Fat, which is a source of energy, fat-soluble vitamins and essential fatty acids, is important in the diets of athletes. High-fat diets are not recommended for athletes.
Athletes who restrict energy intake or use severe weight-loss practices, eliminate one or more food groups from their diet, or consume high- or low-carbohydrate diets of low micronutrient density are at greatest risk of micronutrient deficiencies. Athletes should consume diets that provide at least the Recommended Dietary Allowance (RDA) for all micronutrients.
Dehydration (water deficit in excess of 2% to 3% body mass) decreases exercise performance; thus, adequate fluid intake before, during and after exercise is important for health and optimal performance. The goal of drinking is to prevent dehydration from occurring during exercis,e and individuals should not drink in excess of sweating rate. After exercise, the athlete should drink adequate fluids to replace sweat losses during exercise, approximately 16 to 24 oz (450 to 675 mL) fluid for every pound (0.5 kg) of body weight lost during exercise.
Before exercise, a meal or snack should provide sufficient fluid to maintain hydration, be relatively low in fat and fiber to facilitate gastric emptying and minimize gastrointestinal distress, be relatively high in carbohydrate to maximize maintenance of blood glucose, be moderate in protein, be composed of familiar foods, and be well tolerated by the athlete.
During exercise, primary goals for nutrient consumption are to replace fluid losses and provide carbohydrate(approximately 30 to 60 g per hour) for maintenance of blood glucose levels. These nutrition guidelines are especially important for endurance events lasting longer than an hour when an athlete has not consumed adequate food or fluid before exercise, or if an athlete is exercising in an extreme environment, such as heat, cold, or high altitude.
After exercise, dietary goals are to provide adequate fluids, electrolytes, energy, and carbohydrates to replace muscle glycogen and ensure rapid recovery. A carbohydrate intake of 1.0 to 1.5 g/kg (0.5 to 0.7 g/lb) body weight during the first 30 minutes and again every 2 hours for 4 to 6 hours will be adequate to replace glycogen stores. Protein consumed after exercise will provide amino acids for building and repair of muscle tissue.
In general, no vitamin and mineral supplements are required if an athlete is consuming adequate energy from a variety of foods to maintain body weight. Supplementation recommendations unrelated to exercise, such as folic acid for women of child-bearing potential, should be followed. A multivitamin/mineral supplement may be appropriate if an athlete is dieting, habitually eliminating foods or food groups, is ill or recovering from injury, or has a specific micronutrient deficiency. Single-nutrient supplements may be appropriate for a specific medical or nutritional reason, such as iron supplements to correct iron deficiency anemia.
Athletes should be counseled regarding the appropriate use of ergogenic aids. Such products should only be used after careful evaluation for safety, efficacy, potency and legality. [Editor's note: An ergogenic aid is any substance used for the purpose of enhancing performance while exercising or competing, such as caffeine or sports drinks, as well as a wide range of nutritional, pharmacologic or physiologic products.]
Vegetarian athletes may be at risk for low intakes of energy, protein, fat, and key micronutrients such as iron, calcium, vitamin D, riboflavin, zinc, and vitamin B-12. Consultation with a sports dietitian is recommended to avoid these nutrition problems.