Betaine (trimethylglycine) is a modified amino acid that normally participates as a cofactor in many reactions essential for normal cell function, including the synthesis of creatine, carnitine, and epinephrine, as well as in the detoxification of homocysteine. Betaine also helps to preserve cell volume and function during the stress of intense exercise. Clinical studies show that betaine may help to promote endurance and optimize muscle output and performance during exercise. Betaine may also help to support a healthy body composition when used along with a healthy diet and exercise program.