Besides muscle-building, aerobic exercise like distance running may also burn some protein for energy. That's why it is important for all athletes to have adequate protein intakes. However, these increased protein needs can be met quite easily without using protein supplements or consuming high-protein diets. Increasing basic foods to meet your increased energy needs will supply more than enough protein. Eating high-protein diets or taking protein supplements may prove harmful and may lead to loss of appetite, diarrhea, dehydration, and undue stress on the kidneys.
Extra protein is also expensive.
Increased physical activity increases calorie needs. For the body to use these extra calories, you may need greater amounts of nutrients such as riboflavin, thiamin, niacin, and iron. But again, increasing nutritious foods to meet increased energy needs should supply more than enough vitamins and minerals. Experts agree that the basis of good nutrition is a well-balanced diet and that vitamin supplements are no substitute for it. Some people think that athletes should take potassium supplements.