TMG (betaine)
Trimethylglycine / betaine anhydrous · Performance
A methyl donor with one well-established effect and one popular claim that keeps not replicating.
What the evidence says
Betaine lowers homocysteine reliably — that is established enough that it is an approved treatment for inherited homocystinuria. Whether lowering homocysteine improves cardiovascular outcomes is a separate and largely negative literature. The strength and power-output claims come from a handful of small trials with inconsistent results. It also appears in NAD+ stacks as a methylation buffer, which is mechanistic reasoning rather than trial evidence.
What studies used
Homocysteine studies used around 3–6 g/day; performance trials commonly used 2.5 g. Published studies had not established a preferred timing.
Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.
Watch out for
- High doses can raise LDL cholesterol in some studies — worth knowing if lipids are already a concern
Evidence base
established literature
Strong human evidence: either a phase 3 or 4 trial report alongside review-level evidence, or ten or more randomised controlled trial reports.
This letter measures how much human research exists, not whether it works for you — the tier above (Moderate) is the read on quality.
Research (12)
- Guidelines for the diagnosis and management of cystathionine beta-synthase deficiencyJ Inherit Metab Dis · 2017
- Effects of chronic betaine supplementation on exercise performance: Systematic review and meta-analysisJ Sports Sci · 2024
- Betaine alleviates cognitive impairment induced by homocysteine through attenuating NLRP3-mediated microglial pyroptosis in an m(6)A-YTHDF2-dependent mannerRedox Biol · 2024
- Betaine and aging: A narrative review of findings, possible mechanisms, research perspectives, and practical recommendationsAgeing Res Rev · 2025
- Homocystinuria: Therapeutic approachClin Chim Acta · 2016
- Betaine Supplementation Improves 60 km Cycling Time Trial Performance and One-Carbon Metabolism in Cyclists During RecoveryNutrients · 2025
- Betaine inhibits the stem cell-like properties of hepatocellular carcinoma by activating autophagy via SAM/m(6)A/YTHDF1-mediated enhancement on ATG3 stabilityTheranostics · 2025
- Impact of natural betaine supplementation on rumen fermentation and productive performance of lactating Damascus goatsTrop Anim Health Prod · 2023
- Betaine supplementation improves CrossFit performance and increases testosterone levels, but has no influence on Wingate power: randomized crossover trialJ Int Soc Sports Nutr · 2023
- Effects of betaine supplementation on cardiovascular markers: A systematic review and Meta-analysisCrit Rev Food Sci Nutr · 2022
- Betaine supplementation and blood lipids: fact or artifact?Nutr Rev · 2006
- Effects of Betaine Supplementation on Muscle Strength and Power: A Systematic ReviewJ Strength Cond Res · 2017
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