Dietary macro- and micronutrient requirements of endurance athletes.

Most endurance athletes train for many hours per week to compete in events which generally last no longer than 23 h. However, there are exceptions and these include the full-course triathlon in which competitors swim 2.5 km (l.Smiles), cycle 180km (112miles) and finally run 42.2 km (26.2 miles). Elite athletes win this competition in a little over 8 h. In cycling, there are competitions which last for 2-3 weeks, such as the Tour de France, the Giro de Italia or Vuelta Ciclista a Espana. Gruelling as these competitions are, the preparation required to complete them is as impressive as the events themselves. Daily training is a way of life for endurance athletes and so they should be aware of the best ways to restock their fuel stores. Although research interest in the metabolic responses to exercise has grown exponentially throughout the last century, there were no research-based nutritional recommendations to guide athletes in their preparation for training and competition. In an attempt to redress the balance, an International Consensus Conference was convened in 1991 to review the scientific literature on the links between food, nutrition and sports performance (Devlin & Williams, 199 1). The Consensus Conference concluded that the most significant influence on endurance capacity was the size of an athlete’s pre-exercise carbohydrate stores, i.e. muscle and liver glycogen concentrations. The Consensus Conference recommended that athletes should eat a diet in which carbohydrate-containing foods provide between 60 and 70% of their daily energy intake, fat should provide no more than 30% and protein should provide the remainder of their energy requirements. The very high carbohydrate intakes were not intended to be part of the athletes’ habitual diet but part of the short-term preparation for, and recovery from, heavy exercise. The Consensus Conference also concluded that if athletes eat a wide variety of foods in sufficient quantity to cover their daily energy expenditure, then there are no benefits to be gained from supplementing their diets with additional vitamins and minerals (Devlin & Williams, 1991). The exceptions are those athletes who reduce their energy intake to lose body mass as part of a strategy to improve their performance. A reduction in their macronutrient intake will result in an inadequate intake of micronutrients. Young female athletes who reduce their food intake are at particular risk of receiving less than they need of Fe, Ca and folic acid. Furthermore, frequent attempts to ‘diet’ to compete at a lower body mass can lead to a range of eating disorders (Sundgot-Borgen, 1993). Athletes tend to overestimate their need for protein and underestimate the importance of fluid balance. Even in the power sports, where strength is essential for success, the protein requirements of these athletes is only of the order of 1.7-2.0g/kg body weight (BW; Lemon, 1991b). In contrast, endurance athletes require a daily protein intake of only 1.2-1.5 g/kg BW (Lemon, 1991~). Thus, endurance athletes can achieve these recommendations for protein intake without modifying their habitual diets.