L-Methionine is an essential amino acid that cannot be synthesized by the human body and must be obtained from the diet. It is one of the building blocks of proteins and is involved in various physiological processes. L-Methionine is important for the synthesis of various compounds in the body, including creatine, carnitine, and polyamines. It is also a precursor to the amino acid cysteine, which is important for the production of glutathione, a powerful antioxidant. L-Methionine is commonly found in animal protein sources, such as meat, fish, and dairy products, as well as in plant-based sources, such as beans, nuts, and seeds. It is also available in supplement form.