TMG (Trimethylglycine): The Powerful Methyl Donor Most People Have Never Heard Of

If you've been researching methylation support, you've likely come across TMG — also known as trimethylglycine or betaine. It's one of the most powerful and most underappreciated supplements for homocysteine management, and it works through a completely different biological pathway from standard B vitamins.

What Is TMG?

TMG (trimethylglycine) is a naturally occurring compound found in highest concentrations in beetroot, spinach, quinoa, and wheat germ. It is structurally glycine with three methyl groups attached — hence 'tri-methyl-glycine'. It is one of the most efficient methyl donors in human biochemistry.

How TMG Lowers Homocysteine

There are two main pathways through which homocysteine is cleared from the body. The remethylation pathway converts homocysteine to methionine using methylfolate and methylcobalamin B12 — this is the pathway that depends on MTHFR function. The betaine-homocysteine methyltransferase (BHMT) pathway also converts homocysteine to methionine, but uses TMG (betaine) as the methyl donor instead of methylfolate — and it does not depend on MTHFR. This is why TMG is so valuable for people with MTHFR variants: it provides an alternative route to homocysteine clearance that bypasses the impaired MTHFR step entirely.

The Clinical Evidence

Multiple clinical trials have demonstrated that TMG supplementation significantly reduces elevated homocysteine. A 2003 randomised controlled trial found that 6g of betaine daily reduced fasting homocysteine by approximately 20% in people with elevated levels. Betaine supplementation is used clinically in the management of homocystinuria — the severe genetic condition of homocysteine metabolism. Combined supplementation with both TMG and methylated B vitamins produces greater homocysteine reduction than either alone.

TMG and Liver Health

Beyond homocysteine management, TMG plays an important role in liver function. It is required for the synthesis of phosphatidylcholine — a key component of liver cell membranes and a component of bile. TMG supplementation has shown benefit in non-alcoholic fatty liver disease (NAFLD) in several studies, reducing liver fat and improving liver enzyme markers. For people with significant alcohol use history, fatty liver, or liver stress from medication or toxin exposure, TMG is a particularly valuable addition to a methylation support protocol.

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