The effect of walnut (Juglans regia L.) intake on improvement of blood lipid levels and vascular health: A meta-analysis

Purpose: Walnut is known to have unique favorable fatty acids, phytochemicals, and other nutrient profiles. As a result, there has been growing interest in evaluation of its health benefit related to cardiovascular disease (CVD). Although inverse associations of nut consumption and risk factors of cardiovascular disease have been reported in many epidemiological studies and qualitative reviews, few meta-analysis studies have been reported. This meta-analysis was conducted in order to evaluate the effect of a walnut-enhanced diet on CVD risk factors.

Methods: We searched Pubmed, Cochrane, Science Direct, and KISS (Korean studies Information Service System) through July 2014. A random-effects meta-analysis was conducted on 17 trials reporting total cholesterol (TC), 14 trials reporting LDL cholesterol (LDL-C), 15 trials reporting HDL cholesterol (HDL-C), 17 trials reporting triglyceride (TG), and four trials reporting flow-mediated dilation (FMD).

Conclusion: Findings of this meta-analysis provide consistent evidence that walnut-enhanced diet intake reduces the CVD risk factors.

Results: In meta-analysis, intake of a walnut-enhanced diet resulted in significantly lowered TC, LDL-C, and TG by -0.124 mmol/l (95% CI, -0.209, -0.039; p = 0.004), -0.085 mmol/lL (95% CI, -0.167, -0.004; p = 10.039), and -0.080 mmol/l (95% CI, -0.155, -0.004; p = 0.039), respectively. The overall pooled estimate of the effect on FMD was +1.313% (95% CI, 0.744, 1.882, p = 0.000). HDL-C was not affected by walnut intake. No statistical heterogeneity was observed for any analysis. Results of funnel plots and Egger's regression suggested a low likelihood of publication bias in all biomarkers (p > 0.05).