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.