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

Jin Sook Kwak; Min young Park; Oran Kwon

doi:10.4163/jnh.2014.47.4.236

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

Research Article

Journal of Nutrition and Health 2014; 47(4): 236-246.

Published online: 31 August 2014

DOI: https://doi.org/10.4163/jnh.2014.47.4.236

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

Jin Sook Kwak^1,², Min young Park², Oran Kwon^2,³

¹BrofoodCRO Co., Ltd, Seoul 120-160, Korea.

²Department of Nutritional Science and Food Management, Ewha Womans University, Seoul 120-750, Korea.

³Biofood Network Center, Ewha Womans University, Seoul 120-750, Korea.

To whom correspondence should be addressed. tel: +82-2-3277-6860, orank@ewha.ac.kr

Received 20 July 2014 Revised 13 August 2014 Accepted 15 August 2014

(open-access):

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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).

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 = l0.039), 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).

Conclusion

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

Keywords: Meta-analysis, walnut, Juglans regia, blood lipid level, flow-mediated dilation

Figures and Tables

Fig. 1

Flow diagram of included and excluded studies.

Fig. 2

Forest plot results of the effect of walnut intake on A: total cholesterol, B: LDL-cholesterol, C: HDL-cholesterol, D: Triglyceride, E: Flow-mediated dilation.

Fig. 3

Funnel plot showing the effect of the walnut intake on changes in A: Total cholesterol, B: LDL-cholesterol, C: HDL-cholesterol, D: Triglyceride, E: Flow-mediated dilation.

Table 1

Details of randomized controlled trials included in this meta-analysis

1) CO: cross-over, SB: single-blind, DB: double-blind 2) HC: hypercholesterolemia, MetS: metabolic syndrome, DM: diabetes 3) TC: total cholesterol, LDL-C: low density lipoprotein cholesterol, HDL-C: high density lipoprotein cholesterol, TG: triglyceride, FMD: flow-mediated dilation

Table 2

Results of subgroup analysis by dosage, duration and, subject

1) TC: total cholesterol, LDL-C: low density lipoprotein cholesterol, HDL-C: high density lipoprotein cholesterol, TG: triglyceride

2) CI: confidence interval

^*: p < 0.05

Table 3

Restriction sensitivity and heterogeneity analysis

1) TC: total cholesterol, LDL-C: low density lipoprotein cholesterol, HDL-C: high density lipoprotein cholesterol, TG: triglyceride

2) CI: confidence interval

^*: p < 0.05

Notes

This work was supported by the Rural Development Administration in 2014 (PJ008450022014).

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