Effects of curcumin supplementation on inflammatory biomarkers in patients with Rheumatoid Arthritis and Ulcerative colitis: A systematic review and meta-analysis

Background: Although previous studies have examined the impact of curcumin supplementation on cytokine levels in patients with autoimmune disorders, we were unable to find a systematic review of the effect of curcumin supplementation on inflammatory biomarkers such as CRP and ESR in patients with rheumatoid arthritis or ulcerative colitis; therefore we conducted this systematic review and meta-analysis. Methods: Relevant studies published from inception to December 2020 were systematically searched through the PubMed, SCOPUS, and google scholar databases. We conducted our systematic review and meta-analysis according to the 2020 PRISMA guidelines. The quality of the papers were assessed by using the Cochrane Collaboration's risk of bias tool. Included studies were randomized clinical trials on the effects of supplementation with curcumin or its derivative on inflammatory factors in patients with rheumatoid arthritis and ulcerative colitis. Pooled effect sizes were calculated using a random-effects model and reported as the weighted mean difference (WMD) and 95 % CI. Results: In all, six studies met the inclusion criteria for this study. Curcumin supplementation in doses of 250-1500 mg/day over 8-12 weeks was observed to be associated with decreases in CRP and ESR in adult patients with rheumatoid arthritis and ulcerative colitis in comparison with the control group (WMD: -0.42; 95 % CI: -0.59, - 0.26, I2 = 94.3 %; WMD: -55.96; 95 % CI: -93.74, -18.17, I2 = 99.7 %, respectively). Significant findings were also observed based on subgroup analyses by the study sample size, duration, participants' age, curcumin dosage, and type of disease. Conclusions: Curcumin supplementation was associated with significant reductions in levels of CRP and ESR in patients with rheumatoid arthritis and ulcerative colitis. Earlier studies reported curcumin as a safe complementary therapy for several diseases. However, a handful of studies were found on the effect of curcumin on autoimmune diseases despite our comprehensive search. Further studies are therefore warranted in this area.