HealthWise L-Methionine is an essential amino acid, found in foods not commonly eaten by vegans or vegetarians. It contributes to the synthesis of S-adenosyl-L-methionine (SAMe), which is necessary for normal brain function, and L-Cysteine, which is a component of glutathione, an important antioxidant molecule in the body. Methionine is also a transporter of the antioxidant mineral, selenium. L-Methionine helps to break down fats and assists with Choline production and transport of selenium and zinc. Cells in the liver and kidneys especially need this amino acid for regeneration. Signs of L-Methionine deficiency include poor skin tone, hair loss and impaired elimination of toxins.