By Lindsay Edwards

Some athletes follow a high-carbohydrate diet to improve their performance. Such a diet may result in low levels of zinc, however, and may actually adversely affect strength and endurance. The Agricultural Research Service (the chief scientific agency of the U.S. Department of Agriculture) conducted a study on the effects of zinc levels in 12 athletic men in their twenties.

The men were placed on two diets, each lasting nine weeks. In the first diet, the men consumed an amount of zinc slightly higher than the recommended daily allowance (about 18 milligrams). In the second nine weeks, the men were placed on diets that contained an exceptionally low level of zinc (about three milligrams per day). The finding suggested that after the low-zinc diet, the men were more sluggish when doing a high-intensity workout. Their energy production was lower.

However, the scientists warn, don't assume that more zinc will give you more energy. Zinc can inhibit copper utilization and uptake in the body, which can promote anemia. It can also lower levels of HDL (good) cholesterol that's associated with a reduction in cardiovascular disease.