Curcumin on Human Health: A Comprehensive Systematic Review and Meta-Analysis of 103 Randomized Controlled Trials

The aim of this meta-analysis was to determine the effect of curcumin on a range of health outcomes. PubMed, EMBASE, Scopus, and Web of Science were searched from inception until September 2023. Randomized clinical trials (RCTs) that compared the effect of Curcuma longa L. with placebo were considered eligible. The risk of bias and overall certainty of evidence were assessed using the Newcastle-Ottawa Scale and Grading of Recommendations Assessment, Development, and Evaluation (GRADE), respectively. We meta-analyzed the effect sizes across eligible studies using the random-effects model. In total, 103 RCTs on 42 outcomes were included, incorporating a total population of 7216 participants. Overall, 23 out of 42 (55%) outcomes reported statistically significant effect sizes. The credibility of the evidence was rated as high for fasting blood sugar (FBS), C-reactive protein (CRP), high-density lipoprotein (HDL), and weight. The remaining outcomes presented moderate (waist circumference [WC], hip circumference [HC], body mass index [BMI], insulin, Homeostatic Model Assessment for Insulin Resistance [HOMA-IR], quantitative insulin-sensitivity check index [QUICKI], leptin, gamma-glutamyl transferase [GGT], glutathione [GSH], and superoxide dismutase [SOD]), low (14 outcomes), or very low (14 outcomes) evidence. In conclusion, curcumin supplementation can modify FBS and some glycemic indices, lipid parameters, as well as inflammatory and oxidative parameters. This updated summary of the accumulated evidence may help inform clinicians and future guidelines regarding medical and scientific interest in curcumin. However, due to limitations in the methodological quality of the included studies, well-designed and long-term RCTs with large sample sizes are needed. Trial registration: PROSPERO: CRD42021251969.