If you are an athlete what amounts of carbohydrates should you consume and why. Why are carbohydrate inportant if you are an athlete?

christie hutchings, Great Britain (UK)

The energy the body requires for every physical activity is obtained from the body stores or the food we eat. The amount depends on the duration and type of activity. The human digestive system converts the carbohydrates in food into glucose and is carried in the blood and transported to cells for energy. Any glucose not used by the cells is converted into glycogen - a form of carbohydrate that is stored in the muscles and liver. The body`s glycogen capacity is limited to about 300 to 400 grams. Once this maximum has been reached, any excess glucose is converted into fat.

During training and competition an athlete`s glycogen stores are depleted. In order to replenish them, the athlete needs to consider the speed at which carbohydrate is converted into blood glucose and transported to the muscles. An intake of between 30 grams to 60 grams of carbohydrate an hour is recommended (1). This is about the maximum your muscles can take up from the bloodstream during exercise. Greater amounts have no further benefit. It is best to start taking in carbohydrate soon after the exercise session begins because of the delay in absorption.

For the athlete, carbohydrates should provide 60 per cent to 70 per cent of total dietary energy. The rise in blood glucose levels is indicated by a food`s Glycaemic Index (GI), and the faster and higher the blood glucose rises the higher the GI will be. It is beneficial to consume lower GI carbohydrates, which are absorbed slowly over a longer period of time.

The vital role of physical activity in maintaining health and fitness is now generally recognised. For those who want to keep fit and active, a well-balanced high-carbohydrate diet is recommended. There is now substantial evidence that carbohydrates can improve the performance of athletes. During high intensity exercise, carbohydrates are the main fuel for the muscles. Glycogen stores will be kept well stocked if high levels of carbohydrate are consumed before, during and after training or an event. These stocks help the athlete to perform over longer periods and help their bodies sustain the effort.

(1) Coggan, A. R. and Coyle, E. F. (1991), Carbohydrate ingestion during prolonged exercise: effects on metabolism and performance, in J. Holloszy (ed.), Exercise and Sports Science Reviews, vol. 19 (Baltimore: Wiliams & Wilkins), pp. 1 - 40