Does betaine do anything for strength or power?

Betaine (trimethylglycine, or TMG) started as a byproduct of beet-sugar refining and ended up as a gym-supplement staple, usually dosed at 1.5-2.5 g and stacked into pre-workouts. The pitch rests on two real mechanisms: betaine is an osmolyte that helps cells hold water and resist stress, and it’s a methyl donor that feeds the pathway converting homocysteine back into methionine - the same pathway involved in making creatine and S-adenosylmethionine. Both are legitimate biochemistry. What’s shakier is whether either one actually shows up on the platform.

The best current answer comes from a 2024 meta-analysis pooling 17 trials and 317 people: chronic betaine, taken for at least a week, produced a small-to-moderate effect on maximal strength overall, driven mostly by lower-body lifts (squat-type 1RM, isometric or isokinetic leg force). Vertical jump improved slightly too, once one low-quality study was excluded. Upper-body strength, cycling sprint power, and bench-throw power showed nothing. That split matters - this isn’t a supplement that lifts everything a little, it’s one that might help your squat and your jump and stops there.

Zoom into the individual trials and it gets messier. The 2010 crossover study that helped launch betaine’s reputation found gains in both upper-body measures (bench throw power, isometric bench force) and some lower-body ones (vertical jump power, isometric squat force) — though squat-jump power specifically and reps-to-failure on either lift didn’t move. A 2017 systematic review of seven RCTs called the strength/power case weak - only two of the seven found anything positive. A well-controlled trial in untrained women found betaine sped up fat loss during a resistance program but didn’t move squat or bench 1RM any more than placebo did. And six weeks of betaine in trained CrossFit athletes changed nothing meaningful in strength or body composition.

Why the results scatter

Doses, training status, and rep schemes vary across these studies, and most samples are small - a dozen to two dozen people per trial. Lower-body, multi-joint lifts hold up more consistently than isolated power tests, but with this little data that could just be where the noise happens to land rather than a real biological pattern.

Bottom line

If you’re already taking 2.5 g a day, it isn’t doing harm and might nudge lower-body strength a little, especially early in a training program. It isn’t reliable enough to build a program around, and don’t expect it to touch your bench or your sprint.