(P03-092-23) The Influence of Daily Walnut Intake on Vascular Function and Lipid Metabolism in Overweight and Obese Postmenopausal Women

Objectives: Previous studies report that daily walnut intake can reduce total and low-density lipoprotein (LDL) cholesterol and improve vascular function. Walnut-derived essential polyunsaturated fatty acids (PUFA), linoleic and alpha linolenic acids, may mediate some of these health benefits. Metabolites of these fatty acids, called oxylipins, are known for their biological effects including regulation of inflammation, vasodilation, and platelet reactivity. The purpose of this study was to assess the influence of incorporating 40g/d of walnuts into the habitual diet for 12 weeks on microvascular function and lipid metabolism.

Methods: Twenty overweight and obese, postmenopausal women, aged 45 to 65 years, were enrolled in an 18-week dietary intervention trial. The trial consisted of 4 study visits scheduled 6 weeks apart. This study design allowed for data collection from an individual’s habitual diet for 6 weeks followed by 12 weeks of daily walnut intake. The primary endpoint was microvascular function as measured by reactive hyperemia index (RHI). Secondary outcome measures included plasma cholesterol and plasma and lipoprotein-esterified oxylipins assessed by liquid chromatography–mass spectrometry. Each participant’s 12-week supplemental walnut period was compared to their initial 6 weeks of habitual diet, with interindividual changes evaluated using repeated measures analysis of variance.

Results: Preliminary findings suggest a significant increase in RHI (p=.03) with daily consumption of 40g/d walnuts for 12 weeks. When considering only those whose RHI was at or below the median (2.4) at baseline, statistical significance increased (p=0.00023). Over the course of the trial, total cholesterol and LDL-cholesterol did not significantly change (p=.20 and p=.19, respectively), although the overall trend was towards reduced levels. Participants with elevated total cholesterol (TC >200 mg/dL) and LDL-cholesterol ( >130 mg/dL) at baseline experienced more pronounced reductions (P=.10 and p=.14, respectively) than those in the optimal range.

Conclusions: Daily addition of walnuts to the habitual diet improved vascular health and lipid profile in overweight and obese, postmenopausal women, particularly in those at higher cardiovascular risk at baseline.

Funding Sources: California Walnut Commission