Methionine is one of the two sulfur containing amino acids. Strings of amino acids make up proteins. We don't use protein directly. Our digestive system must break down protein into individual amino acids. Amino acids are absorbed into the blood stream and provided as nutrients to our cells. Methionine is found in all foods but more abundant in animal foods than most plant foods. Methionine is a building block of proteins necessary for cell growth and is also utilized as a methyl donor. Methyl groups are involved in DNA signaling and gene expression.