Trimethylglycine (TMG), also called betaine, is a substance manufactured by the body. It helps break down another naturally occurring substance called homocysteine.

In certain rare genetic conditions, the body cannot dispose of homocysteine, resulting in its accumulation to extremely high levels. This, in turn, leads to accelerated cardiovascular disease and other problems. Oral TMG is an FDA-approved treatment for this condition. It "methylates" homocysteine, removing it from circulation.

Meaningful, but not altogether consistent, evidence suggests that the relatively slight elevation of homocysteinethat can occur in healthy people is also harmful.6 On this basis, it has been suggested that TMG might reduce heart disease risk in healthy people as well. However, this has not been proven, and TMG has shown the potential for having adverse effects on cholesterol profile, which could counter any possible benefit via homocysteine.

Note: TMG is similar chemically to betaine hydrochloride, but it has entirely different actions.

TMG is not required in the diet because the body can manufacture it from other nutrients. Grains, nuts, seeds, and meats contain small amounts of TMG. However, most TMG in food is destroyed during cooking or processing, so food isn't a reliable way to get a therapeutic dosage.

After TMG has done its work on homocysteine, it is turned into another substance, dimethylglycine (DMG). Some manufacturers will tell you that DMG is identical to TMG, but this isn't true. DMG is not a methylating agent, so it can't have any effect on homocysteine. (See also Therapeutic Uses below.)