Betaine (TMG): The Homocysteine and Pre-Workout Supplement

By Erin Rose · Updated July 19, 2026 · Methodology

Educational overview — not medical advice. Betaine (TMG) is not an approved treatment for cardiovascular disease, fatty liver, or any other condition. This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.

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What betaine (TMG) is, and the naming trap that confuses everyone

Betaine — also called trimethylglycine or TMG — is a naturally occurring compound (found in beets, wheat bran, spinach, and seafood) that functions two ways in the body: as an organic osmolyte protecting cells from stress, and as a methyl donor that remethylates homocysteine back into methionine in the liver and kidney (Craig 2004). It's sold as a supplement for two distinct reasons — homocysteine/methylation support and pre-workout power — and this page covers both honestly, including where the evidence falls short.

The naming trap, stated plainly: "betaine" on a supplement label almost always means one of two very different products. Betaine anhydrous / TMG — the subject of this entire cluster — is the methyl-donor/osmolyte compound discussed here. Betaine HCl (betaine hydrochloride) is a separate stomach-acid and digestive-enzyme product, usually sold combined with pepsin, marketed for low-stomach-acid symptoms. Different mechanism, different use case, different evidence base entirely — this page does not cover betaine HCl, and none of the homocysteine or performance evidence below applies to it. If you're looking for digestive support, see the betaine HCl cluster instead — including the honest reckoning on whether it actually fixes "low stomach acid."

Thread one: homocysteine — reliable, but a surrogate marker with a trade-off

This is the most-replicated effect in the betaine literature. Olthof et al. 2003 randomized 76 healthy adults to 1.5g, 3g, or 6g/day betaine vs placebo for 6 weeks and found fasting homocysteine fell 12%, 15%, and 20% respectively — a clean, dose-dependent result. Schwab et al. 2006 showed the effect is even acute: single 3g and 6g doses lowered plasma homocysteine within 2 hours, while a 1g dose did not. Betaine anhydrous is even an FDA-approved prescription drug (Cystadane) for homocystinuria, a rare genetic disorder of homocysteine metabolism — real-world clinical confirmation that betaine reliably moves this biomarker, though at doses well above general-population supplement ranges and under medical supervision, not a reason a healthy person should self-dose at drug-level amounts.

But two honest caveats travel with every homocysteine claim, every time. First: homocysteine is a surrogate marker, not a disease outcome. No outcome trial in this evidence base — or in the broader homocysteine-lowering literature generally — shows that betaine supplementation reduces heart attacks, strokes, or cardiovascular mortality. Lowering a biomarker is not the same as preventing disease, and this page never implies otherwise. Second: Olthof et al. 2005, a combined analysis of three betaine RCTs (n=151), found that 6g/day — the dose with the clearest homocysteine effect — raised LDL cholesterol by 0.36 mmol/L and triglycerides by 0.14 mmol/L. That's a real trade-off at the effective dose, not a rounding error, and it's especially relevant if you're already managing elevated cholesterol. See the full homocysteine breakdown for both threads together.

Thread two: athletic performance — a genuinely mixed picture

At ~2.5g/day, seven sports-performance trials in this evidence base tell a mixed story. Lee et al. 2010 found increased bench throw power and isometric bench press force in trained men, with benefits "more apparent in the smaller upper-body muscle groups" — but jump squat power showed no difference. Cholewa et al. 2013 and Cholewa et al. 2018 (the latter with a disclosed DuPont Nutrition & Health funding tie) both found body-composition improvements — but neither found a 1-rep-max strength advantage on bench press or squat, the primary strength outcome, over placebo. A hot-weather running/sprint trial (Armstrong et al. 2008) found only a nonsignificant trend the authors themselves said "did not definitively support" betaine for sprint performance. The honest verdict: some signal, mostly on secondary/body-composition endpoints, never on 1RM strength itself. Full synthesis on does betaine work for strength.

A mechanism reference worth naming: methyl donor, not proven outcome

Betaine's mechanism — osmolyte plus methyl donor in the methionine cycle — is real biochemistry (Craig 2004), but mechanism is not the same as a proven human outcome. That distinction matters most for liver health: betaine's methylation role has led to "detoxes the liver" marketing, but the one dedicated NAFLD trial (Abdelmalek et al. 2009) gave 20g/day — a research dose far above supplement range — to diagnosed NASH patients for 12 months and found no improvement on NAFLD activity score or fibrosis stage, the outcomes that matter. NAFLD evidence for betaine is preliminary and largely negative, not a treatment claim this site makes.

Frequently asked questions

Related guides

• Creatine — fellow pre-workout/power-output ingredient, the natural best-overall cross-link
• Beta-Alanine — fellow pre-workout ingredient with its own honest-dosing angle
• L-Carnitine — another amino-acid-adjacent performance supplement
• Choline — a fellow methyl donor, with its own TMAO/methylation-cycle honesty story
• Methylfolate — remethylates homocysteine via a separate pathway
• Vitamin B12 — the third leg of the homocysteine-remethylation triad, alongside folate and betaine

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