What the evidence says. Graded moderate: meta-analyses reliably show betaine lowers homocysteine (~12%) and a modest lower-body strength signal (ES ~0.49), but it has no proven effect on cardiovascular events, raises total/LDL cholesterol, and body-composition trials directly conflict. (Moderate evidence: Several controlled trials; effects real but modest or context-dependent.)
What is Betaine (TMG)?
Betaine (TMG) (Trimethylglycine) is a performance supplement used for lower plasma homocysteine. NutriDex grades the human evidence as Moderate. Betaine (trimethylglycine, TMG) is a methyl donor found in beets and whole grains. Its best-replicated effect is lowering plasma homocysteine: a meta-analysis of 5 RCTs found 4-6 g/day cut it by about 1.23 micromol/L (~12%). Whether this translates to fewer heart events is unproven, and the same and later meta-analyses show betaine moderately raises total and LDL cholesterol (~14 and ~10 mg/dL), which may offset any benefit. For exercise, a 2024 meta-analysis (17 trials) found a small significant gain in maximal strength, concentrated in the lower body (ES ~0.49), with no effect on upper-body or power measures. Body-composition results conflict outright: one meta-analysis found modest body-fat loss, another found none. A 12-month NASH trial improved liver steatosis on imaging but not fibrosis. Overall: a real but narrow biomarker and strength effect, no hard outcomes.
Purported Benefits
✓Lower plasma homocysteine
✓Lower-body strength & power
✓Support liver fat metabolism
✓Osmolyte / cell hydration
Evidence by outcome
The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.
Outcome
Evidence
Effect
Studies
Lowers plasma homocysteineTwo meta-analyses consistently show ~12% / ~1.2-1.3 umol/L reduction at 4-6 g/day; surrogate marker, no hard outcomes.
Strong
↑ benefit · moderate
2
Raises total/LDL cholesterolMeta-analysis and RCT show total/LDL rise (~14/~10 mg/dL), potentially offsetting any homocysteine benefit.
Moderate
⚠ risk · small
2
Increases lower-body maximal strength17-trial meta-analysis found small strength gain (ES 0.47) confined to lower body; no effect on upper body or power.
Moderate
↑ benefit · small
1
Reduces body fatOne meta-analysis found fat loss (-2.5 kg), another found no effect; results conflict outright.
2.5 g/day (split) for performance; 4-6 g/day to lower homocysteine. Betaine HCl is a separate digestive product, not interchangeable.
Active Compounds
Trimethylglycine (anhydrous betaine)
Safety & Cautions
⚠
Generally well tolerated; at high doses (>4-6 g/day) it can cause nausea, diarrhea, GI upset and a fishy body odor (trimethylaminuria). Its main concern is raising total and LDL cholesterol, so people with dyslipidemia or cardiovascular risk should be cautious. No major drug interactions are established, but because it lowers homocysteine it may add to the effect of B-vitamins/folate; the high-dose prescription form (Cystadane, for inborn homocystinuria) has rarely caused cerebral edema. Discuss with a clinician if you have heart disease, kidney disease, or are pregnant. Educational only — always check with your doctor or pharmacist before combining Betaine (TMG) with any medicine.
Betaine (TMG) is most often taken for Lower plasma homocysteine, Lower-body strength & power, Support liver fat metabolism, Osmolyte / cell hydration. Methyl donor that lowers homocysteine and may aid lower-body strength.
Does Betaine (TMG) work — what does the evidence say?
Moderate evidence. Several controlled trials; effects real but modest or context-dependent. Betaine (trimethylglycine, TMG) is a methyl donor found in beets and whole grains. Its best-replicated effect is lowering plasma homocysteine: a meta-analysis of 5 RCTs found 4-6 g/day cut it by about 1.23 micromol/L (~12%). Whether this translates to fewer heart events is unproven, and the same and later meta-analyses show betaine moderately raises total and LDL cholesterol (~14 and ~10 mg/dL), which may offset any benefit. For exercise, a 2024 meta-analysis (17 trials) found a small significant gain in maximal strength, concentrated in the lower body (ES ~0.49), with no effect on upper-body or power measures. Body-composition results conflict outright: one meta-analysis found modest body-fat loss, another found none. A 12-month NASH trial improved liver steatosis on imaging but not fibrosis. Overall: a real but narrow biomarker and strength effect, no hard outcomes.
What is the typical dose of Betaine (TMG)?
2.5 g/day (split) for performance; 4-6 g/day to lower homocysteine. Betaine HCl is a separate digestive product, not interchangeable.
Is Betaine (TMG) safe? Any cautions or side effects?
Generally well tolerated; at high doses (>4-6 g/day) it can cause nausea, diarrhea, GI upset and a fishy body odor (trimethylaminuria). Its main concern is raising total and LDL cholesterol, so people with dyslipidemia or cardiovascular risk should be cautious. No major drug interactions are established, but because it lowers homocysteine it may add to the effect of B-vitamins/folate; the high-dose prescription form (Cystadane, for inborn homocystinuria) has rarely caused cerebral edema. Discuss with a clinician if you have heart disease, kidney disease, or are pregnant.
How many studies support Betaine (TMG)?
NutriDex cites 10 sources for Betaine (TMG), graded "Moderate".
Cite this page
APA
Peh, D. (2026). Betaine (TMG) (Trimethylglycine): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/betaine-tmg
BibTeX
@misc{nutridex_betaine_tmg,
author = {Peh, Daryl},
title = {Betaine (TMG) (Trimethylglycine): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/betaine-tmg},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.