Effects of betaine supplementation on inflammatory markers: a systematic review and meta-analysis of randomised controlled trials.

Several studies have suggested that betaine is closely related to inflammatory biomarkers that contribute to the development of metabolic diseases, but the effect remains controversial. This meta-analysis aimed to assess the effects of betaine supplementation on inflammatory markers based on randomised controlled trials (RCTs). PubMed, Web of Science and ResearchGate databases were searched up to March 2023. A total of 6 RCTs with 7 intervention trials involving 277 participants were included. Betaine supplementation led to a slight reduction in levels of circulating IL-1β of 0.65 pg/mL (95% CI, -1.23 to -0.06) with high heterogeneity (I² = 95%). Betaine produced a small but nonsignificant reduction in levels of circulating CRP (0.33 mg/L; 95% CI, -1.79 to 1.14), IL-6 (0.47 pg/mL; 95% CI, -1.13 to 0.18) and TNF-α (0.25 pg/mL; 95% CI, -0.98 to 0.48). The present meta-analysis does not provide sufficient evidence to conclude that betaine supplementation improved the inflammation state.