The clinical efficacy of curcumin-containing nutraceuticals: An overview of systematic reviews

Background: The clinical efficacy of curcumin-containing nutraceuticals (e.g. turmeric preparations, curcumin, curcuminoids) for a range of conditions has been assessed by several systematic reviews, in some instances with contradictory conclusions. Our aim was to provide an up-to-date and rigorous synthesis of these data and to evaluate the quality of the available systematic reviews. Methods: Electronic searches were conducted (up to December 2017) to locate all systematic reviews (SRs) related to the use of curcumin-containing nutraceuticals for any condition. The quality of the retrieved SRs was assessed by using AMSTAR an OQAQ tolls. Results: Twenty-two SRs met our inclusion criteria. Overall, four SRs were of high quality using the AMSTAR scale, whereas twelve SRs achieved an high quality classification according to the OQAQ score. There is some evidence that curcumin-containing nutraceuticals can exert systemic antioxidant actions (1 SR) and may be effective i) in inflammatory conditions such as arthritis-related diseases and inflammatory bowel disease (12 SRs), ii) in reducing lipid levels and cardiovascular risk factors (5 SRs) as well as iii) in skin diseases (1 SR). Cautious preliminary positive results were reported for depressive disorders (3 SRs), while no efficacy was observed in Alzheimer's disease patients (1 SR). Curcumin-containing nutraceuticals appear to be safe, as assessed by the adverse events reported in twelve SRs. Conclusions: Based on the currently available SRs, the efficacy of curcumin-containing nutraceuticals has been demonstrated for several conditions; however, due to the poor quality of the primary trials and the low-to-moderate level of some SRs, there is still some uncertainty.