Betaine (TMG)
Trimethylglycine
TL;DR
Betaine (TMG) donates methyl groups to clear homocysteine and is taken at 2.5 g/day, with modest evidence for strength and body composition in trained lifters.
Ideal For
- Resistance-trained lifters seeking a small edge in lean mass
- People with elevated homocysteine
- Those with an MTHFR variant affecting methylation
- People with non-alcoholic fatty liver disease seeking adjunct support
Avoid If
- You have elevated LDL cholesterol
- You have kidney disease, without medical supervision
- You are pregnant or breastfeeding
Frequently Asked Questions
Overview
Betaine, also called trimethylglycine, was first isolated from sugar beet and is found in beetroot, spinach, quinoa and wheat bran. Typical dietary intake is 100-400 mg/day, well below supplemental doses. Its two roles are distinct: it donates a methyl group to convert homocysteine back to methionine, and it acts as an organic osmolyte that helps cells maintain volume under stress.
The homocysteine effect is the best documented. Doses of 3-6 g/day lower plasma homocysteine reliably, and betaine anhydrous is an approved treatment for inherited homocystinuria. Whether that lowering reduces cardiovascular events is unresolved, and higher doses can raise LDL cholesterol, which complicates the picture.
In sport, roughly a dozen small trials at 2.5 g/day have examined strength, power and body composition in resistance-trained men. Results are mixed but lean positive for lean mass and repeated-effort work, with less consistent effects on one-rep max. Effect sizes are small, and most trials ran six to eight weeks. Betaine also supports hepatic fat export via phosphatidylcholine synthesis, which is why it appears in fatty liver research.
How It Works
- Donates a methyl group via betaine-homocysteine methyltransferase, regenerating methionine
- Acts as an organic osmolyte, stabilising cell volume and protein structure under stress
- Supports phosphatidylcholine synthesis needed to export fat from the liver
- Increases creatine synthesis indirectly by supporting methionine availability
- May improve cellular hydration during resistance exercise
Quick Facts
- Supports methylation
- Enhances power output
- Improves body composition
- Liver health support
- Lowers homocysteine
Benefits & Outcomes
Homocysteine Reduction
Betaine lowers homocysteine independently of folate, especially post-methionine load.
Power Output Enhancement
Some resistance-training studies report improved power, others find nothing.
Enhanced Athletic Performance
Betaine anhydrous shows promise for strength and body composition, but trials conflict.
Liver Protection
Betaine has plausible mechanisms and small positive trials in fatty liver disease, but results are inconsistent.
Heart Health Support
Betaine lowers homocysteine, but higher doses can raise LDL cholesterol, muddying the cardiovascular picture.
Health Concerns Addressed
No linked health concerns yet.
Supporting Research4 studies
Betaine supplementation decreases plasma homocysteine in healthy adult participants: a meta-analysis
McRae MP
Betaine supplementation of at least 4 g/day significantly reduced plasma homocysteine concentrations in healthy adults compared with placebo.
The effects of betaine supplementation on fluid balance and heat tolerance during passive heat stress in men
Willingham BD, Renteria LI, Ragland TJ +1 more
Consuming intracellular osmolytes, like betaine (BET), may attenuate symptoms of heat stress.
Effects of chronic betaine supplementation on exercise performance: systematic review and meta-analysis
Zawieja E, et al.
Chronic betaine supplementation produced small improvements in some strength and power measures, with no consistent effect on endurance performance.
Effects of Betaine Supplementation on Muscle Strength and Power: A Systematic Review
Ismaeel A
Of the trials reviewed, several reported improvements in strength or power with betaine while others found no significant effect versus placebo.
Safety Information
Potential Side Effects
Generally well tolerated. Gastrointestinal upset, diarrhoea and a fishy body odour at higher doses. The clinically relevant effect is a rise in LDL cholesterol at doses above about 4 g/day.
Contraindications
Higher doses raise LDL cholesterol and total cholesterol in some trials, so use caution if lipids are already elevated. Use in kidney disease should be supervised.
Drug Interactions
- No clinically established drug interactions
- Works alongside folate and B12 in the methylation cycle — deficiency in either limits the benefit
Pregnancy & Breastfeeding
Pregnancy: insufficient_data
Breastfeeding: insufficient_data
Dosage Guidelines
Dosage Used in Studies
500-3000 mg
Best Time to Take
Split between breakfast and a pre-training meal
Best Form
Betaine anhydrous — betaine HCl is a different product for a different purpose
Bioavailability
Well absorbed. Methyl donor supporting methylation cycle. Converts homocysteine to methionine. May support liver function. Often combined with B vitamins for synergy.
Forms Compared
Betaine anhydrous
Betaine HCl
Dietary sources
Food & Timing
With meals; splitting the dose reduces the fishy aftertaste some people notice
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.