July 13, 1999 CHAMPAIGN, Ill. -- Athletes have been advised for years that carbohydrates and amino acids can enhance their performance. Now, it appears that timing of the right food -- in addition to fluid replacement -- may be crucial to post-exercise recovery.
Based on a series of experiments using rats, University of Illinois scientists say swifter recovery occurs when foods containing leucine, a branch-chained amino acid, are eaten immediately after intensive workouts. Leucine is found in protein products such as meats and dairy products, as well as in protein bars and some sports drinks. The use of a pure amino-acid supplement is not recommended, because optimum dosages are not known.
"Leucine appears to have a specific, and apparently unique, impact on skeletal muscle," said Donald K. Layman, a professor of nutrition. "It stimulates muscle protein synthesis, provides fuel for the muscle and helps to maintain blood glucose. What really surprised us was that its activity is not seen when leucine or protein is consumed before or during exercise. Instead it has a dramatic impact on protein synthesis during the recovery period after exercise."
In the tests, rats were divided into five groups based on sedentary or exercised activity levels and combinations of food (leucine or carbohydrates or both). Researchers then studied muscle recovery after some of the rats ran on a treadmill. The exercised rats fed leucine and carbohydrates (a sugar and water combination) immediately after running showed quicker recovery of muscle protein synthesis.
The findings by Layman and graduate students Josh Anthony and Tracy Gautsch appeared in the June issue of the Journal of Nutrition. The National Institutes of Health funded the research.
"It appears that leucine stimulates a signaling pathway somewhat like the hormone insulin," Layman said. "It has been debated whether the action of leucine was simply confused with the action of insulin. Our research shows that there is a unique role of leucine, and that it runs almost parallel to insulin. It appears that leucine stimulates the first step in protein synthesis."
Based on the U. of I. research, Layman suggests that athletes:
-- Consume dietary protein of 1.4 to 2.0 grams per kilogram of body weight per day to obtain the necessary level of leucine to help with muscle development. An athlete weighing 175 pounds (79.5 kg) should eat from 111 to 159 grams a day. (Convert pounds to kilograms by dividing by 2.2)
-- Immediately after exercise, consume a low-fat, protein-rich food such as lean lunch meat or a protein drink or bar. Also include plenty of carbohydrate-rich fluids.
-- Maintain a balanced diet that contains carbohydrates, fat and protein, with the protein making up 30 percent of the calories, at every meal, including snacks. Such a diet differs from current recommendations that suggest meals of 60 percent to 70 percent carbohydrates and protein of less than 20 percent of calories.
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