Effect of curcumin on proinflammatory cytokines: A meta-analysis of randomized controlled trials

It has been suggested that curcumin has the potential for lowering inflammation. In the current meta-analysis, we attempted to clarify the efficacy of curcumin/turmeric supplementation in reducing concentrations of interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-α in patients with an inflammatory background. The main databases were searched to identify eligible trials evaluating the effect of curcumin in reducing IL-1, IL-6, IL-8, and TNF-α in serum up to March 2021. The effect sizes for weighted mean difference (WMD) and 95% confidence intervals (CI) were calculated. Overall, 32 randomized controlled trials (RCTs) were included. There was a significant decrease in the serum levels of IL-1 (WMD = -2.33 pg/ml, 95% CI = -3.33 to -1.34, P < 0.001) and TNF-α (WMD = -1.61 pg/ml, 95% CI = -2.72, -0.51, P < 0.001) compared to the placebo group following treatment. Nonetheless, curcumin/turmeric supplementation was non-significantly associated with reduced levels of IL-6 (WMD = -0.33 pg/ml, 95% CI = -0.99-0.34, P = 0.33) and increased levels of IL-8 (WMD = 0.52 pg/ml, 95% CI = -1.13-2.17, P = 0.53). The dose-responses analysis indicated that curcumin/turmeric supplementation resulted in IL-1 and IL-8 alteration in a non-linear model. Subgroup analysis according to duration and dose of treatment and target population revealed diverse outcomes. Curcumin could have a beneficial effect in reducing the proinflammatory cytokines IL-1 and TNF-α, but not IL-6 and IL-8 levels.