L-methionine (also just called methionine), is an essential amino acid (one that can't be produced by the body), and which is found in meat, fish and dairy products. L-methionine supplements are available in capsules and bulk powder.
L-methionine (methionine) promotes the development of cartilage tissue. A 2016 study on rats found that a high-Methionine (high-Met) diet is capable of reducing the adverse effects of arthritis.
In the body, L-methionine (methionine) converts to SAMe (S-adenosyl-methionine), which is a popular supplement for treating mood and anxiety disorders. However, the ability of SAMe to penetrate the blood-brain barrier is limited, and a 2005 study found that use of L-methionine (methionine) "caused larger increases in brain SAMe at lower doses."