Betaine Anhydrous: Power, Methylation & Hypertrophy — A Research-Backed Guide
⚡ 60-Second Summary
Betaine anhydrous (trimethylglycine, TMG) is a naturally occurring compound found in beetroot, spinach, wheat germ, and quinoa. It functions as both a cellular osmolyte — accumulating in cells to protect against osmotic stress — and as a methyl group donor in the one-carbon metabolic cycle, converting homocysteine to methionine. Several RCTs show meaningful improvements in strength, power, and lean mass at the standard dose of 2.5 g/day.
Note on TMAO: Like L-carnitine, betaine can be converted by gut bacteria to TMA and then TMAO. The cardiovascular significance is debated but worth awareness, particularly in those with existing heart disease.
Typical dose: 2.5 g/day — the dose used in key performance RCTs. Split into two doses of 1.25 g or taken pre-workout. Stacks well with creatine and citrulline.
What is betaine anhydrous?
Betaine (trimethylglycine) is the trimethylated form of the amino acid glycine. It occurs naturally throughout the animal and plant kingdom as an osmoprotectant — compounds that accumulate inside cells during osmotic stress to maintain water balance without disrupting enzyme function. Rich dietary sources include beetroot (~330 mg/100g), spinach (~645 mg/100g), wheat germ (~1,240 mg/100g), and quinoa (~390 mg/100g). Average dietary intake is approximately 1–2.5 g/day in Western diets.
In human metabolism, betaine is a major methyl group donor in the betaine-homocysteine methyltransferase (BHMT) pathway, donating a methyl group to homocysteine to form methionine. This reaction is critical for reducing elevated homocysteine, synthesizing S-adenosylmethionine (SAM — the universal methyl donor), and supporting creatine biosynthesis. As an osmolyte in skeletal muscle, betaine may support cell volume and hydration under exercise stress, which is hypothesized to contribute to its ergogenic effects.
Evidence-based benefits of betaine anhydrous
1. Power output and strength
Lee et al. (2010, n=12) showed that 2.5 g/day betaine for 14 days improved power output and muscle endurance in cycling sprints. Apicella et al. (2013) found increased growth hormone and IGF-1 responses to exercise with betaine supplementation. A 2017 meta-analysis (Gao et al.) found modest but significant improvements in strength and power outcomes across 8 studies, though effect sizes vary and some individual studies show null results.
2. Lean mass and hypertrophy
Cholewa et al. (2013, n=23) is the key study: 2.5 g/day betaine for 6 weeks in resistance trainers produced significantly greater increases in lean mass (+1.8 kg vs +0.8 kg placebo), arm circumference, and bench press volume. Body fat decreased more in the betaine group. These results have been replicated by some but not all subsequent studies. The mechanism likely involves betaine's role in creatine synthesis (as a methyl donor for guanidinoacetate methylation) and potential anabolic signaling via GH/IGF-1 and mTOR pathways.
3. Homocysteine reduction
Betaine's methyl-donation role in BHMT is well established. Clinical studies consistently show that 2.5–6 g/day betaine reduces elevated plasma homocysteine by 10–20%. This is relevant in individuals with elevated homocysteine (a cardiovascular risk factor), MTHFR variants, or inadequate folate/B12 status. Betaine works through a parallel pathway to folate and B12 for homocysteine remethylation.
4. Exercise endurance in heat stress
Betaine's osmoprotective function may reduce physiological strain during exercise in hot environments. Armstrong et al. (2008) found reduced heart rate, body temperature, and perceived exertion during heat-stressed exercise with betaine supplementation. This is a niche but practically relevant application for athletes training in warm climates.
Appropriate use
Betaine is a reasonable addition to pre-workout stacks for resistance training athletes seeking additional power and hypertrophy support beyond creatine and beta-alanine. It is also rational for individuals with elevated homocysteine. The evidence is moderately strong for body composition and power, though less consistent than creatine. Not primarily an endurance supplement.
Betaine forms compared
| Form | Notes |
|---|---|
| Betaine anhydrous (powder) | Most studied form. Dissolves well. The pure trimethylglycine compound. Slightly bitter taste easily masked in pre-workout blends. |
| BetaPower (natural betaine) | Trademarked betaine derived from sugar beets. Same compound as synthetic betaine anhydrous; some performance claims differentiate natural sourcing. |
| Betaine HCl | Betaine hydrochloride — a different product used primarily as a digestive aid to provide hydrochloric acid for low-stomach-acid conditions. Not a performance supplement. Commonly confused with betaine anhydrous (TMG). |
How much betaine anhydrous should you take?
- Performance (standard dose): 2.5 g/day — the dose in key performance RCTs
- Split vs single: Can be split into 2 doses of 1.25 g (with breakfast and pre-workout) or taken as a single pre-workout dose
- Homocysteine reduction: 2.5–6 g/day; physician-supervised for clinical homocysteinemia
- Duration: Benefits accumulate with consistent use; most studies run 6 weeks to 8 weeks
- With food: Taken with meals or mixed into pre-workout drinks
Safety, TMAO, and side effects
Betaine anhydrous at 2.5–6 g/day has been well tolerated in all published human trials. High dietary betaine intakes from food (up to 10 g/day) are considered safe.
- Fishy body odor: In some individuals with trimethylaminuria (TMAU) — a condition where TMA conversion to TMAO is impaired — betaine can cause a fishy body odor. This is rare in the general population.
- GI effects: Nausea or GI discomfort at doses >4 g/day in some individuals. Splitting doses mitigates this.
- TMAO: Like carnitine, betaine can elevate plasma TMAO via gut microbial conversion. This concern is less studied for betaine than for carnitine, and the clinical significance for cardiovascular risk from food-derived betaine (e.g., from beets) appears low. Those with existing cardiovascular disease may wish to discuss with their physician.
Drug and nutrient interactions
- Methotrexate: Methotrexate inhibits folate-dependent homocysteine remethylation; betaine (via BHMT pathway) may partially compensate. Discuss with your oncologist or rheumatologist if relevant.
- Folate and B12: Synergistic for homocysteine reduction — betaine, folate, and B12 work via parallel remethylation pathways. Combining for elevated homocysteine is rational.
- Creatine: Betaine contributes methyl groups to creatine biosynthesis; taking both together is complementary rather than redundant.
- Anticoagulants: Betaine does not have known interactions with blood thinners at supplemental doses.
Check our free interaction checker for additional combinations.
Who might benefit — and who shouldn't bother
| Most likely to benefit | Unlikely to benefit or should exercise caution |
|---|---|
| Resistance training athletes seeking power and hypertrophy support beyond creatine | People with trimethylaminuria (fishy odor condition) |
| Individuals with elevated homocysteine (MTHFR variants, low B vitamins) | Those on methotrexate without physician guidance |
| Athletes training in hot environments (osmoprotective effect) | People expecting creatine-level performance gains — betaine evidence is good but not as extensive |
| Vegetarians and vegans with low dietary betaine (primarily grain/vegetable eaters) | People with established cardiovascular disease (discuss TMAO concern) |
Frequently asked questions
How much betaine anhydrous should I take?
2.5 g/day is the standard dose used in key performance RCTs. Split into two 1.25 g doses or take as a single pre-workout dose. Most studies run 6–8 weeks; benefits accumulate with consistent use.
Does betaine increase muscle mass?
Several RCTs show significantly greater lean mass gains at 2.5 g/day vs placebo in resistance trainers, with the Cholewa et al. (2013) study being the most cited. Not all studies replicate this finding, but the meta-analysis evidence leans positive. Betaine is likely a meaningful addition to a performance stack, not a replacement for creatine or protein.
Does betaine raise TMAO?
Yes, betaine can be converted by gut bacteria to TMA and then TMAO. The cardiovascular significance of betaine-derived TMAO appears less established than for carnitine; food-derived betaine (from beets and spinach) is not generally considered a cardiovascular concern at typical dietary levels. Supplemental doses in people with existing cardiovascular disease warrant a conversation with their physician.
What is the difference between betaine anhydrous and betaine HCl?
Betaine anhydrous (TMG) is trimethylglycine — the osmolyte and methyl donor used in performance supplements. Betaine HCl (betaine hydrochloride) is a different product used as a digestive acid supplement to treat low stomach acid (hypochlorhydria). They have completely different applications and should not be confused.
Related ingredients and articles
Creatine
The most evidence-backed performance supplement — betaine supports creatine biosynthesis.
Citrulline Malate
Blood flow and pump — commonly stacked with betaine in pre-workout formulas.
Carnitine Liquid
Another TMAO-raising compound — understand the parallel considerations.
Best Pre-Workout Stacks (2026)
How betaine fits in modern pre-workout formulations.
Disclaimer: This information is for educational purposes only and should not replace medical advice. Always consult a qualified healthcare provider before starting any supplement, especially if you have a medical condition, are pregnant, or take prescription medications. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.