BCAA stands for branched chain amino acids and is increasingly being recognized as an important supplement in the field of sports nutrition. In short the term refers to three essential amino acids - leucine, isoleucine and valine. Amino acids are widely known as the building blocks of protein. When protein food is eaten it gets digested into individual amino acids and short chains of amino acids that are sufficiently small to be absorbed into the bloodstream. They are then used by the body to build and repair tissues amongst other things. Amino acids are split between those classed as essential and those labelled non-essential. This simply means that essential amino acids cannot be made by the body, whereas non-essential amino acids can. There are nine essential amino acids and each must be obtained from the diet. The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Non-essential amino acids are just as important as the essential variety and the term simply means they can be made by the body from vitamins and other amino acids. The non-essential amino acids are alanine, arginine, asparagine, aspartic acid, cysteine, cystine, glutamic acid, glutamine, glycine, proline, serine and tyrosine. The BCAA's are especially important to athletes because they are metabolized in the muscle rather than the liver. This means that they can be used either to build new proteins or be burned as fuel to create energy. Supplementing with BCAA's has been shown to result in measurable gains in both muscle strength and size. Taken before a workout BCAA's can improve performance and delay the onset of fatigue. They also operate as anabolic agents allowing the body to burn fat and not muscle. As a supplement that has no reported side effects, branched chain amino acids offer many benefits to the serious bodybuilder.