Are curcuminoids effective C-reactive protein-lowering agents in clinical practice? Evidence from a meta-analysis

Background: Inflammation plays a pivotal role in the pathogenesis of atherosclerosis and cardiovascular disease (CVD). In this context, C-reactive protein (CRP) has been identified as a strong predictor and independent risk factor of CVD. Curcuminoids are multifunctional natural product with promising cardioprotective and anti-inflammatory properties. Curcuminoids have been suggested to lower circulating levels of CRP, but clinical findings have not been consistent.

Objectives: To pool the published results of clinical trials on the impact of supplementation with curcuminoids on circulating levels of CRP.

Methods: PubMed/MEDLINE and SCOPUS databases were searched for clinical trials reporting circulating CRP changes in individuals receiving curcuminoids. Effect sizes with 95% confidence intervals (CI) were calculated using a random-effects model. Inter-study heterogeneity was assessed using Cochran's Q and I(2) tests. Sensitivity analyses were conducted using leave-one-out method.

Results: Six trials comprising 172 subjects in the curcuminoids group and 170 subjects in the placebo group fulfilled the eligibility criteria and included in the meta-analysis. Compared with placebo, supplementation with curcuminoids was associated with a significant reduction in circulating CRP levels (weighed mean difference: -6.44 mg/L; 95% CI: -10.77 - -2.11; p = 0.004). This significant effect was maintained in subgroups of trials that used bioavailability-improved preparations of curcuminoids and had supplementation duration of ≥4 weeks, but not in the subgroups without these characteristics.

Conclusions: Supplementation with curcuminoids may reduce circulating CRP levels. This effect appears to depend on the bioavailability of curcuminoids preparations and also duration of supplementation. Future well-designed and long-term trials are warranted to verify this effect of curcuminoids.