Trimethylglycine (TMG) is also called glycine betaine, but the name trimethylglycine signifies that it has three methyl groups attached to each molecule of glycine. Wheat bran is the main dietary source of TMG, with smaller amounts available in other cereal grains.
TMG can also be made in the body from choline, an essential nutrient found in eggs, soybeans and many other foods.