S-adenosyl-L-methionine (SAMe) is a naturally occurring substance formed in the body from the amino acid methionine and the "energy molecule" adenosine triphosphate (ATP). The formation of SAMe is catalyzed by methionine adenosyltransferase and depends on cofactors such as vitamin B6, vitamin B12, folate, and magnesium. SAMe has been studied as a supportive nutrient for liver health, joint comfort, metabolic reactions, and healthy mood.