Methionine is one of the sulfur-containing amino acids (cysteine and cystine are others) and is important for many bodily functions. Through its supply of sulfur, it helps prevent problems of the skin and nails. It acts as a lipotropic agent (others are inositol and choline) to prevent excess fat buildup in the liver and the body, is helpful in relieving or preventing fatigue, and may be useful in some cases of allergy because it reduces histamine release. It also may help lower an elevated serum copper level. Methionine works as an antioxidant (free radical deactivator) through conversion to L-cysteine to help neutralize toxins. However, L-cysteine is used more often than methionine as an antixoidant because it seems to be better tolerated and has a wider range of protection.