L-Methionine is an essential amino acid that we need to live. It is used to make proteins in the body. It is also important for metabolism and growth. It can be found in protein rich foods such as meat, eggs, fish, and legumes. L-Methionine can be produced in the body from another amino acid, methionine. However, during times of stress, such as fever, infection, pregnancy, or strenuous exercise, the body is unable to produce enough methionine to keep up with demands, so supplementation can help.