Sports nutrition. Approaching the nineties.

A sophisticated appreciation of the role of nutrition in athletic performance has been made possible by increasing knowledge of the physiology of exercise. The nutritional issues of training are of primary importance, since this occupies most of the athlete's effort. The nutritional support of an intense daily training programme includes an appropriately high energy intake, predominantly in the form of carbohydrate in order to continually replenish muscle glycogen stores. Recent review of the protein needs of athletes indicates that requirements may be substantially above those of sedentary subjects, to account for the oxidation of amino acids during exercise as well as the retention of nitrogen during periods of muscle building. However, these increased requirements are likely to be met by the generous protein intakes anticipated in a high energy diet. The same would seem to hold true for micronutrient considerations, although there is no evidence that vitamin requirements are considerably increased by exercise. Nevertheless, a high energy diet chosen from a sufficiently varied range of foods should allow micronutrient intakes well in excess of population recommended dietary intake levels. Current interest is focused on the mineral status of athletes, particularly that of iron and calcium. In the case of iron, there is a possibility that the increased level of loss by some endurance athletes will not be met by their usual dietary patterns. Screening for early signs of iron deficiency, and appropriate supplementation and dietary counselling seem warranted in high risk groups. Competition poses the challenge of identifying possible factors limiting performance, and taking steps to delay or reduce these. Of paramount importance is body temperature regulation through the maintenance of hydration levels. This issue has long been recognised, but recent studies of gastric emptying and the benefits of carbohydrate supplementation during exercise have caused an update of the advice to athletes regarding fluid intake during exercise. It now seems possible to simultaneously achieve fluid and carbohydrate requirements for endurance exercise within a wide range of choice of beverages containing up to 10% carbohydrate. Concern about the adequacy of carbohydrate fuel stores in endurance exercise situations is also well known. The recognition that training achieves various physiological adaptations to enhance the lifespan of fuel stores has taken away some of the attention previously focussed on carbohydrate-loading techniques.(ABSTRACT TRUNCATED AT 400 WORDS)