Benefits
Athletic performance — power and strength
Multiple RCTs demonstrate betaine (2.5 g/day) significantly increases muscle power output, strength, and anaerobic capacity. Studies show improvements in vertical jump power, sprint speed, squat volume load, and bench press work capacity — with effect sizes comparable to creatine in some trials. Betaine is now considered one of the best-supported ergogenic aids alongside creatine.
Body composition improvement
A 6-week study showed betaine (2.5 g/day) combined with resistance training produced significantly greater lean body mass gains and fat mass reduction compared to placebo plus identical training. The proposed mechanism involves betaine's role as a methyl donor for creatine synthesis and IGF-1 signaling pathway activation.
Homocysteine reduction and cardiovascular protection
Betaine is one of the most effective natural agents for reducing elevated homocysteine — a cardiovascular risk factor. As the methyl donor for homocysteine remethylation to methionine via BHMT (betaine-homocysteine methyltransferase), betaine addresses homocysteine through a B-vitamin-independent pathway. Clinically meaningful homocysteine reductions of 10–20% are achieved with 1.5–6 g/day.
Liver protection and methylation support
Betaine reduces hepatic fat accumulation, protects against non-alcoholic fatty liver disease (NAFLD), and supports liver function through methyl group donation for phosphatidylcholine synthesis and SAMe regeneration. Clinical studies show reductions in liver enzymes and hepatic fat with betaine supplementation in NAFLD patients.
Mechanism of action
BHMT-mediated homocysteine remethylation
Betaine donates a methyl group to homocysteine via betaine-homocysteine methyltransferase (BHMT) in the liver and kidneys, converting potentially harmful homocysteine back to methionine. This B-vitamin-independent remethylation pathway complements the folate/B12-dependent methionine synthase route, providing a backup mechanism particularly important when folate or B12 are insufficient.
Cellular osmolyte protection
Betaine accumulates intracellularly as an organic osmolyte, protecting cells from hypertonic stress by balancing water activity without disrupting protein structure. In muscle cells under the osmotic stress of intense exercise, betaine maintains cellular hydration, protein stability, and enzyme activity — improving muscle performance during high-intensity training.
Creatine synthesis substrate provision
Betaine provides methyl groups for guanidinoacetate methylation — the final step in creatine biosynthesis. By increasing the efficiency of the body's endogenous creatine production, betaine amplifies the cellular creatine pool and enhances the phosphocreatine energy system in muscle, contributing to the ergogenic effects observed in strength and power athletes.
Clinical trials
Within-subject crossover study in 12 recreationally trained men examining 14 days of betaine supplementation (1.25 g twice daily, 2.5 g total) on strength and power outcomes including bench press throw power, isometric bench press force, vertical jump power, and isometric squat force. (Lee et al. 2010, J Int Soc Sports Nutr)
12 recreationally trained men (mean age 21). 14-day intervention, within-subject design.
Betaine increased bench throw power, isometric bench press force, vertical jump power, and isometric squat force vs pre-supplementation values. No improvement in jump squat power or rep counts. Effects more pronounced in upper-body movements. Note: small sample, within-subject design without true placebo control limits strength of conclusions.
Randomized, placebo-controlled trial in 23 resistance-trained men receiving betaine (2.5 g/day, n=11) or placebo (n=12) during a 6-week periodized training program. Outcomes: body composition (bench press work capacity, body fat %, lean body mass, fat mass), homocysteine thiolactone (HCTL), training volume. (Cholewa et al. 2013, J Int Soc Sports Nutr)
23 resistance-trained men. 6-week intervention.
Betaine group showed significant improvements in body fat %, fat mass, lean body mass, arm size, and bench press work capacity vs placebo. Trend toward improved vertical jump power (p=0.07). Betaine attenuated the rise in urinary HCTL (a homocysteine metabolite linked to cardiovascular risk). No significant effects on absolute strength (1RM bench, squat).