Supplement analysis backed by scientific evidence · PT

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Limited evidencePhysical performance

Betaine (Trimethylglycine)

Betaine reliably lowers homocysteine and is an approved drug for homocystinuria, but its popular use as a strength and power supplement rests on small, conflicting trials. A 2024 meta-analysis found no meaningful chronic performance benefit, and betaine modestly raises cholesterol.

What the science says

  • Improving strength and power output Limited evidence

    Ismaeel's 2017 systematic review found the evidence mixed: some trials reported improvements in bench press work capacity or power, while roughly as many found nothing. A 2024 systematic review and meta-analysis of chronic betaine supplementation concluded there was no consistent significant improvement in exercise performance outcomes. Trials are small (typically 15-30 participants) and methodologically variable.

  • Lowering plasma homocysteine Strong evidence

    A 2013 meta-analysis found betaine supplementation significantly decreased plasma homocysteine in healthy adults, with doses around 4-6 g/day producing meaningful reductions. Betaine is also an approved prescription therapy (Cystadane) for homocystinuria. Whether lowering homocysteine reduces cardiovascular events, however, remains unproven.

  • Improving body composition Limited evidence

    A few small trials report reduced fat mass or increased lean mass with 2.5 g/day over 6-8 weeks, but results are inconsistent and often based on bioimpedance in small samples. This claim is not adequately supported.

Dosage & safety

Studied dosePerformance studies almost universally use 2.5 g/day, usually split into two 1.25 g doses, for 2-8 weeks. Homocysteine-lowering studies use 3-6 g/day. Betaine is also obtained from food, with wheat bran, spinach and beets among the richest sources (a typical diet supplies 100-400 mg/day).
SafetyGenerally well tolerated at 2.5-6 g/day; GI upset, nausea and a distinctive fishy body odour (from trimethylamine) are the common complaints. Meaningful caveat: a 2021 systematic review and meta-analysis found betaine supplementation moderately increases total and LDL cholesterol, which partly offsets any homocysteine benefit and is a real consideration for people with dyslipidaemia. Betaine raises TMAO precursors. Prescription-strength betaine anhydrous is used for homocystinuria and requires monitoring; cerebral oedema has been reported in that clinical setting at high doses. Not banned in sport.

Scientific references

Where to buy

Nutricost, Betaine Anhydrous, Unflavored, 17.9 oz (500 g)

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