Betaine moved no hormone in women, trial finds

Betaine has picked up a following in supplement circles partly on the strength of reports that it raises total testosterone in physically active men. Whether that finding extends to women had never been tested, which is a familiar gap in supplement research. Sex hormones matter beyond reproduction, influencing body composition, mood and metabolic health, and women with overweight or obesity often have altered hormone profiles. So the question of whether a cheap, widely available compound nudges those hormones in women is worth asking directly rather than extrapolating from male data.

The researchers ran a double-blind, randomised controlled trial in premenopausal women aged 18 to 45 with overweight or obesity, enrolling 36 participants. Each was allocated to receive either 3 g per day of betaine or a matching placebo for eight weeks. Participants attended two study visits, before and after the supplementation period, at the Department of Human Nutrition and Dietetics at Poznań University of Life Sciences in Poland, with data collected between September 2024 and April 2025. Biological samples taken at both visits were analysed by ELISA for a panel of sex hormones, including both plasma and salivary testosterone.

There were no significant time-by-treatment interactions for any hormone measured. Plasma testosterone showed p = 0.496 and salivary testosterone p = 0.882, both comfortably non-significant. Plasma DHEA-S came in at p = 0.498, SHBG at p = 0.775 and oestradiol at p = 0.378. Cortisol, included as a stress-related marker, showed p = 0.504. In other words, across six separate hormonal outcomes, betaine supplementation was indistinguishable from placebo. The authors state plainly that no statistically significant effect was detected, while noting that larger and longer-term studies are needed to confirm the finding.

This is the first test of betaine's hormonal effects in women, and it does not reproduce in this population what had been reported in physically active men. That could mean the effect is genuinely sex-specific, or that it depends on training status, or simply that 36 participants over eight weeks was not enough to detect a small change. Null results in small trials are ambiguous by nature. What the study does usefully establish is that there is no evidence base for marketing betaine as a hormone modulator for women.

If you have seen betaine promoted on the basis of testosterone findings, this is a reason to be cautious about assuming those findings transfer to women. Across six hormones, including two different measures of testosterone, this trial found nothing. That is not the same as proving betaine does nothing — a small, short trial can miss a modest effect — but it does mean the claim is currently unsupported in this population. The study also says nothing about betaine's other proposed uses, which were not measured here.