Effects of chronic betaine supplementation on exercise performance: Systematic review and meta-analysis

Zawieja E, Machek S, Zanchi NE, Cholewa J, Woźniewicz M · Journal of Sports Sciences

Betaine improved maximal strength (SMD 0.47, 95% CI 0.04-0.89), an effect carried by the lower body (SMD 0.49, 95% CI 0.01-0.98), and vertical jump after one low-quality study was excluded (SMD 0.36, 95% CI 0.03-0.69). Upper-body strength, cycling sprint power and muscular endurance did not move.

Population

Healthy people aged 15-60 across 17 chronic betaine trials (21% female)

Intervention

Chronic betaine supplementation for at least 7 days, typically 2.5 g/day

Comparator

Placebo

Limitations

317 participants across 17 mostly small trials with wide confidence intervals that nearly touch zero; heavily male; performance outcomes, not joint or cartilage outcomes.