The American College of Sports Medicine in association with the Academy of Nutrition and Dietetics and the Dietitians of Canada have published an update of the dietary recommendations for athletes. In their joint position statement, dietary recommendations are given for the appropriate amount and timing of intake for carbohydrate, protein, fluid, vitamins and minerals.
Good nutrition enhances both athletic performance and recovery after exercise. This is the conclusion of the report of the American College of Sports Medicine (ACSM) and the American and Canadian dietitians associations. As an increasing number of studies into the effect of nutrition on sports performance have been published over the last 10 years, it was timely to revise the sports nutrition advice from 2011. The evidence based analysis for the current position statement was undertaken with the cooperation of prominent (sports) dietitians and scientists. Their recommendations are aimed at adults actively participating in competitive sports. An important change in the new advice is that the protein recommendations are based on the intensity and the training status of the athlete and not on the type of athlete (duration versus strength). The 25 page document provides substantive information on the recommended intakes of carbohydrate, protein, fat, fluid and vitamins and minerals for various types of athletes. This article offers a short overview of the recommendations.
Carbohydrate is an essential part of sports nutrition as it provides the main source of energy for the body. Therefore it is important to eat enough carbohydrate before exercise to supplement the energy reserves. Consuming carbohydrate during exercise will provide the body with additional energy to maintain performance. In the report guidelines for the intake of carbohydrate before and during exercise are given.
Table 1 Guidelines for intake of carbohydrate before exercise
Table 2 Guidelines for intake of carbohydrate during exercise
Protein supports the maintenance of muscle mass. Apart from the total quantity of protein, the timing and pattern of protein intake over the day is also important. A protein intake of around 20 grams of protein (or 0.25-0.3 g protein/kg body weight) is most effective for optimising muscle protein synthesis after exercise. Ideally this amount of protein should be consumed within 30 minutes to 2 hours after exercise. This is the period when muscles are most sensitive to the recovery processes and when the body can use the protein optimally.
It is generally advised that endurance athletes have a moderately increased requirement for protein compared to non-athletes. The advice on protein requirements for strength athletes is typically even higher. According to the new advice of the ACSM position stand the requirement for protein depends upon training status with well-trained athletes needing a somewhat smaller quantity than less trained athletes. The intensity of the training is also an important factor and the higher the frequency and the intensity, the greater the protein requirement.
Table 3 Guidelines for protein intake
There is no specific dietary recommendation for athletes with respect to fat. In general, the diet of athletes typically contains between 20 en% and 35 en% fat. A very low fat diet with less than 20 en% fat will not improve athletic performance and the low fat content will make it more difficult to achieve a healthy balanced diet.
The body needs fluid to maintain different functions. It is important for athletes to take in sufficient fluid, to offset the additional fluid losses as a result of sweating during exercise. The amount of fluid depends on a number of factors including the duration and intensity of the exercise, weather conditions, body weight and individual sweat rates. The quantity of fluid lost by athletes via sweat is between 0.3-2.4 litres per hour. Ideally, the athlete should replenish fluid losses as much as possible during exercise. The goal is to limit fluid losses via sweat to less than 2% of body weight during exercise.
It is important to restore fluid balance in the body during the recovery phase. Therefore the following advice applies: 1.25-2.5 litres of fluid per kilo of body weight loss. Alcohol is strongly advised against because of its diuretic effect.
Vitamins and minerals
Apart from the intake of the macronutrients discussed, vitamins and minerals are also important for athletes. The ACSM position stand provides specific recommendations for calcium, iron and vitamin D. In fact these micronutrients are of particular importance to athletes, however intakes can be jeopardized when certain food groups are eliminated from their diets. Some athletes run this risk when cutting out whole food groups in an attempt to lose weight.
Table 4 Guidelines for the intake of calcium, iron and vitamin D
- A lower than recommended calcium intake may occur when athletes do not eat enough (during energy restriction) and/or when avoiding dairy products or other food rich in calcium.
- A daily intake of 1500 mg calcium is recommended for athletes with insufficient energy or menstrual problems. In addition to calcium, vitamin D is important for maintenance of bones.
- Athletes who are regular blood donors, vegetarians or long-distance runners are wise to closely monitor their iron status. For this group iron intake can be increased to more than 18 mg for women and 8 mg for men.
- Iron-rich foods in combination with good dietary sources of vitamin C are beneficial for improving iron status. Supplementation under the supervision of a (sports) dietitian is an option.
- Athletes who do not exercise outside or who exercise after sunset may have a lower vitamin D status.
- Vitamin D intake can be increased through diet combined with a vitamin D supplement.
- The ACSM mentions that supplementation in addition to the current recommended amounts can be useful, but no specific recommendations are given. This is to be determined on an individual basis under the supervision of a (sports) dietitian.
Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. Journal of the Academy of Nutrition and Dietetics, 2016; 116: 501-528.