Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function

Acute Effects of High-Fat Meals Enriched With Walnuts or Olive Oil on Postprandial Endothelial Function

Berenice Cortés, Isabel Núñez, Montserrat Cofán, Rosa Gilabert, Ana Pérez-Heras, Elena Casals, Ramón Deulofeu, Emilio Ros

A walnut diet has been shown to improve endothelial function in hypercholesterolemic subjects. In a crossover study in 12 normolipidemic controls and 12 hypercholesterolemic subjects, we compared the acute vasoactive effects of fatty meals (80 g fat, 35% energy as saturated fatty acids) enriched with either 25 g olive oil or 40 g walnuts. In both groups, brachial artery flow-mediated dilation worsened after the olive oil meal and improved after the walnut meal, but the circulating levels of oxidation and inflammation biomarkers decreased after either meal. Supplemental walnuts reverse the postprandial endothelial dysfunction associated with consumption of a fatty meal.

Objectives

We sought to investigate whether the addition of walnuts or olive oil to a fatty meal have differential effects on postprandial vasoactivity, lipoproteins, markers of oxidation and endothelial activation, and plasma asymmetric dimethylarginine (ADMA).

Background

Compared with a Mediterranean diet, a walnut diet has been shown to improve endothelial function in hypercholesterolemic patients. We hypothesized that walnuts would reverse postprandial endothelial dysfunction associated with consumption of a fatty meal.

Methods

We randomized in a crossover design 12 healthy subjects and 12 patients with hypercholesterolemia to 2 high-fat meal sequences to which 25 g olive oil or 40 g walnuts had been added. Both test meals contained 80 g fat and 35% saturated fatty acids, and consumption of each meal was separated by 1 week. Venipunctures and ultrasound measurements of brachial artery endothelial function were performed after fasting and 4 h after test meals.

Results

In both study groups, flow-mediated dilation (FMD) was worse after the olive oil meal than after the walnut meal (p = 0.006, time-period interaction). Fasting, but not postprandial, triglyceride concentrations correlated inversely with FMD (r = −0.324; p = 0.024). Flow-independent dilation and plasma ADMA concentrations were unchanged, and the concentration of oxidized low-density lipoproteins decreased (p = 0.051) after either meal. The plasma concentrations of soluble inflammatory cytokines and adhesion molecules decreased (p < 0.01) independently of meal type, except for E-selectin, which decreased more (p = 0.033) after the walnut meal.

Conclusions

Adding walnuts to a high-fat meal acutely improves FMD independently of changes in oxidation, inflammation, or ADMA. Both walnuts and olive oil preserve the protective phenotype of endothelial cells.

Abbreviations and Acronyms: ADMA, asymmetric dimethylarginine, ALA, α-linolenic acid, FID, flow-independent dilation, FMD, flow-mediated dilation, MUFA, monounsaturated fatty acids, NO, nitric oxide, PUFA, polyunsaturated fatty acids, sICAM-1, soluble intercellular adhesion molecule 1, SFA, saturated fatty acids, sTNF-R, soluble tumor necrosis factor receptors, sVCAM-1, soluble vascular cell adhesion molecule 1