Curcumin supplementation improves flow mediated dilation and endothelial function; A meta-analysis.

Background
Endothelial dysfunction is an early marker of atherosclerosis. Flow mediated dilation (FMD), measured by ultrasonography, is used to non-invasively assess endothelial dysfunction. Curcumin is a naturally occuring pigment molecule found in turmeric. Curcumin supplementation may improve FMD and thus endothelial dysfunction. We did a systematic review and meta-analysis to analyze the effect of curcumin on endothelial dysfunction.

Methods
Five randomized clinical trials met the inclusion criteria for meta-analysis. Primary outcome was improvement in FMD after curcumin supplementation compared to placebo. Standardized mean difference and Hedges’s G were used for effect size measurement. An effect size of 0.2-0.5 is considered small, 0.5-0.8 is medium and more than 0.8 is large. Publication bias was studied too.

Results
We found curcumin supplementation had an overall effect size (standard difference in means) of 1.379 (95% CI 0.485-2.274, P 0.003) on FMD (Figure 1). The overall Hedge’s g was 1.353 (95% CI 0.47-2.235, P 0.03). This analysis suggests a positive and large ES of curcumin on FMD using a random effect model. Orwin’s fail-safe N showed an additional 63 studies with an intervention effect of 0 would be needed to make the ES of the meta-analysis trivial (<0.1). This suggests a low chance of negative studies having not been reported. Smokers had a smaller increase in FMD compared to non-smokers (ES 1.6 vs. 0.37, p 0.03).

Conclusions
Curcumin supplementation significantly increases the FMD compared to placebo and thus has a beneficial effect on endothelial function. This effect is not strongly noticed in smokers.