Promotes Healthy Homocysteine Levels Dietary Supplement TMG Trimethylglycine (TMG) is also called glycine betaine, but the name trimethylglycine signifies that it has three methyl groups attached to each molecule of glycine. TMG was discovered to be beneficial to heart health back in the 1950s. TMG operates along a pathway similar to that of vitamin B12. It is a “methyl donor,â€