Submitted to: International Journal of Sport Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2000
Publication Date: 6/1/2001
Citation: Lukaski, H.C., Bolonchuk, W.W., Klevay, L.M., Milne, D.B., Sandstead, H.H. 2001. Interactions among dietary fat, mineral status and performance of endurance athletes. International Journal of Sport Nutrition. 11(2):186-198. Interpretive Summary: As athletes seek to boost their training and performance, they look to specific energy sources such as carbohydrate and fat. Traditionally, increasing dietary carbohydrate to about 60% of daily energy intake has been successful in heightening the training intensity and endurance of long distance runners and cyclists. Some but not all studies of endurance athletes have found that increasing fat, rather than carbohydrate, intake promoted endurance. We examined the effects of diets high (about 50% energy intake) in carbohydrate, saturated fat and polyunsaturated fat on the performance of elite cyclists. We found no effect of diet on the capacity of the cyclists to perform maximal exercise. Endurance, however, was impaired by the polyunsaturated fat diet. Additionally, the polyunsaturated fat diet increased body losses of iron and zinc with a lesser effect on magnesium; it also tended to decrease body iron stores, particularly in one cyclist who had the greatest decrement in endurance on the polyunsaturated fat diet. The inconsistent effect of dietary fat on endurance performance may be explained by the type of dietary fat composition and an adverse effect of polyunsaturated fat on iron metabolism. These findings support the consumption of a varied diet that contains whole foods by athletes in training and in preparation for competition. This information will be useful for dietitians and sports medicine professionals who counsel physically active people.
Technical Abstract: Performance measures and mineral metabolism were assessed in three male endurance cyclists who consumed isoenergetic, isonitrogenous diets for 28- d periods in a randomized, crossover design in which dietary carbohydrate, polyunsaturated or saturated fat contributed about 50% of daily energy intake. Peak aerobic capacity [62 mL/(kg x min)] was unaffected by diet. Endurance capacity at 70-75% peak aerobic capacity was significantly decreased with the polyunsaturated fat diet. Significantly less iron and zinc were retained (intake - losses) and fecal losses of these minerals increased significantly when the polyunsaturated fat diet was consumed. Blood biochemical measures of trace element nutritional status were unaffected by diet, except serum ferritin which tended to decrease (p = 0.08) during consumption of the polyunsaturated fat diet. We conclude that diets high in polyunsaturated fat, particularly linoleic acid, impair absorption and utilization of iron and zinc, and possibly magnesium, and may reduce endurance performance. Athletes should be encouraged to consume diets containing a variety of foods.