Methionine When in its natural L-form, methionine is a proteinogen amino acid. It is classed as an essential amino acid and cannot be synthesized by the body itself. This means that a sufficient supply of methionine in the diet or as a dietary supplement is of particular importance. Sulphur compounds occur in all living creatures and have a multitude of functions. Besides cysteine, methionine is the only sulphur-containing amino acid. Furthermore methionine plays an important role in the synthesis of other proteins, such as carnitine or melatonine. Methionine has a fat-dissolving effect and reduces the depositing of fat in the liver. Methionine is an important cartilage-forming substance Methionine strengthens the nails and works to combat hair loss