Oral turmeric/curcumin effects on inflammatory markers in chronic inflammatory diseases: A systematic review and meta-analysis of randomized controlled trials

Turmeric extract or active component curcumin may have anti-inflammatory effects in people with chronic inflammatory diseases. The effect of turmeric or curcumin on a wide range of inflammatory markers has not been evaluated in a systematic review. We performed a systematic review of randomized controlled trials (RCTs) evaluating the effects of oral turmeric or curcumin on inflammatory markers (CRP, hsCRP, IL-1, IL-6, TNF) in patients with a wide range of chronic inflammatory diseases. Pubmed, EMBASE, Scopus, the Web of Science, and the Cochrane library were evaluated until June 2018. Random effects meta-analyses with inverse variance methods and stratified by turmeric or curcumin were performed. Effects were expressed as mean differences (MD) and their 95% confidence intervals (CI). Risk of bias of RCTs was evaluated with the Cochrane tool. Nineteen RCTs were identified; included patients had rheumatic diseases, advanced chronic kidney disease with hemodialysis, metabolic syndrome, and cardiovascular diseases. Turmeric was the intervention in 5 RCTs (n = 356) and curcumin/curcuminoids in 14 RCTs (n = 988). Follow up times ranged between 4 and 16 weeks. One RCT had high risk of bias. In comparison to controls, turmeric or curcumin did not significantly decrease levels of CRP (MD -2.71 mg/L, 95%CI -5.73 to 0.31, p = 0.08, 5 studies), hsCRP (MD -1.44 mg/L, 95%CI -2.94 to 0.06, p = 0.06, 6 studies), IL-1 beta (MD -4.25 pg/mL, 95%CI -13.32 to 4.82, p = 0.36, 2 studies), IL-6 (MD -0.71 pg/mL, 95%CI -1.68 to 0.25, p = 0.15), and TNF alpha (MD -1.23 pg/mL, 95%CI -3.01 to 0.55, p = 0.18, 7 studies). There were no differences between turmeric and curcumin interventions. High heterogeneity of effects was observed for all markers across studies, except hsCRP. Other inflammatory markers such as IL-1 alpha, TNF beta, IL-17, and IL-22 had scarce data. Turmeric or curcumin did not decrease several inflammatory markers in patients with chronic inflammatory diseases.