There is no evidence that protein supplements enhance muscle development, strength, or endurance. Extra protein doesn't help and may even hinder health and performance. The body can't tell the difference between protein obtained from food and protein obtained from expensive protein supplements. When athletes eat more protein than they require, the excess protein is either burned for energy or converted to fat, which many athletes don't realize. Burning protein for energy is expensive and wasteful.
Carbohydrates are a more effective and less costly source of energy.
Consuming too much protein, whether from food or supplements, increases the body's water requirement and may contribute to dehydration. This is because the kidneys need more water to eliminate the excessive nitrogen load imposed by a high protein intake. Athletes on high-protein diets should be sure to drink additional fluids to avoid becoming dehydrated. High-protein diets are also usually high in fat. This type of diet also takes along time to digest and can contribute to feeling sluggish.