The effects of curcumin on anthropometric and cardiometabolic parameters of patients with metabolic related diseases: a systematic review and dose-effect meta-analysis of randomized controlled trials

Objective:To perform a meta-analysis of published randomized controlled trials (RCTs) to assess the effects of curcumin supplementation with different formulations on anthropometric and cardiometabolic indices in patients with metabolism-related diseases (MRDs). Methods: Six databases, including PubMed, Embase, Web of Science, China national knowledge internet (CNKI), Wanfang and China Biology Medicine (CBM), were systematically searched to find relevant articles from 2011 to July 2021. The effect sizes were expressed as weighted mean difference (WMD) with 95% confidence intervals (CI). Between-study heterogeneity was assessed using I-2. Subgroup analysis was conducted to find possible sources of heterogeneity. Curcumin formulations in this study were divided as low bioavailability, high bioavailability and nanocurcumin. Results: Of the retrieved 1585 articles, 31 were included in the final analysis. Combined effect sizes suggested a significant effect of curcumin supplementation on reduced body weight (BW) (WMD: -0.94 kg, 95% CI: -1.40, -0.47) and body mass index (BMI) (WMD: -0.40 kg/m(2), 95% CI: -0.60, -0.19), respectively. The results also showed significant improvements of fasting plasma glucose (FPG) (WMD: -0.50 mg/dL, 95% CI: -0.72, -0.28), glycosylated hemoglobin (Hb1Ac) (WMD: -0.42%, 95% CI: -0.57, -0.26), insulin (INS) (WMD: -1.70 mu IU/mL, 95%CI: -2.03, -1.38), homeostasis model assessment-insulin resistance (HOMA-IR) (WMD: -0.71, 95%CI: -1.11, -0.31), high-density lipoprotein cholesterol (HDL-C) (WMD: 1.73 mg/dL, 95%CI: 0.78, 2.68) and high sensitivity C-reactive protein (Hs-CRP) (WMD: -1.11, 95%CI: -2.16, -0.05). Nanocurcumin showed a greater reduction in FPG (WMD: -1.78 mg/dL, 95% CI: -2.49, -1.07), INS (WMD: -1.66 mu IU/mL, 95% CI: -3.21, -0.11), TC (WMD: -12.64 mg/dL (95% CI: -23.72, -1.57) and LDL-C (WMD: -8.95 mg/dL, 95% CI: -16.51, -1.38). The dose-effect analysis showed that there were trends of first rising and then falling between the supplemented curcumin dose and BW, BMI, LDL-C, Hb1Ac, which were clearly distinguished at 80 mg/d due to the strong effect of nanocurcumin on outcomes. A slow upward trend between the dose of curcumin supplementation and HDL-C. No relationships between dose and outcomes were found for FPG and insulin, except for nanocurcumin at 80 mg/d. Conclusions: Our study showed some significant beneficial effects of curcumin supplementation on improving BW, BMI, and the levels of FPG, Hb1Ac, HOMA-IR, HDL-C and Hs-CRP in patients with MRDs. Nanocurcumin may have a greater effect on the reduction of FPG, INS, TC and LDL-C than other curcumin formulations. Considering the potential bias and limitations of studies included, further quality studies with larger sample sizes are needed to confirm these results.