Betaine (Tmg) for Exercise Performance

Research suggests that betaine supplementation may offer modest benefits for exercise performance, with the most consistent signals appearing in endurance contexts, as demonstrated by a 2025 RCT showing improved cycling time trial performance, and some reviews identifying positive effects on endurance, strength, and body composition across athletic populations. However, the evidence is genuinely mixed: a systematic review of seven RCTs found that only two reported meaningful improvements in muscle strength or power, and a CrossFit-based RCT found no significant ergogenic effect on aerobic or anaerobic performance, while one crossover study found no support for the proposed nitric oxide mechanism. The available literature includes a combination of RCTs, systematic reviews, and narrative reviews, with the latter tending toward more favorable interpretations than the controlled trial data strictly supports. Studies indicate that while betaine shows some promise, particularly when combined with regular physical activity, the inconsistency across study designs, populations, and outcome measures means that clear conclusions about its ergogenic value remain elusive.