High Dose EPA Reduces Arterial Stiffness That Accompanies High-Fat Meals
Various studies have reported that consumption of fish or fish oils may affect vascular function in ways that increase forearm blood flow and arterial elasticity, while reducing blood pressure. However, there is some disagreement about the effects on vascular relaxation of docosahexaenoic acid (DHA), a long-chain omega-3 polyunsaturated fatty acid (n-3 LC-PUFA), in spite of its association with improved endothelial function.
High-fat meals can impair endothelial function and flow-mediated dilation within 3 to 4 hours, the time when peak postprandial lipemia, the rise in blood fats following a meals occurs. Different fatty acids also affect flow-mediated dilation, at least in individuals with type 2 diabetes, with saturated fatty acids reducing it and n-3 PUFAs increasing it. However, others have reported increased forearm blood flow and flow-mediated dilation in healthy volunteers following a fatty meal, changes that were not associated with impaired endothelial nitric oxide release. Increases in flow-mediated dilation may offset reductions in blood flow, helping to maintain healthy vascular reactivity. Diminished endothelial function is believed to contribute to atherosclerosis and diabetes. In this report, the effect of eicosapentaenoic acid (EPA), an n-3 LC-PUFA, on postprandial vascular function, including oxidative stress, nitric oxide production, was examined in 21 healthy, non-smoking, young men, aged 18 to 35 years. Seventeen men completed the study.
After an overnight fast, participants were given a high-fat test meal containing 51 g of fat mainly from high-oleic sunflower oil that included either 5 g of EPA (and about 700 mg DHA) or 7 g of additional oleic acid. Measurements of blood pressure, digital volume pulse to assess arterial stiffness and vascular tone, and plasma isoprostanes, triglycerides and fatty acids were obtained at baseline, 3 and 6 hours after consumption of the test meal. Participants consumed a second high-fat meal containing 44 g fat (26 g saturated fat) after 4 hours to enhance any lipemia-induced change in arterial function and mimic typical eating behavior.
Men consuming the EPA-enriched meals exhibited a steep increase in plasma EPA that peaked 5 hours after the test meals (Figure 1). There was a small, but statistically significant, increase in DHA as well. Neither fatty acid concentration was altered by consumption of the placebo high-oleic acid meal. Arterial stiffness calculated from the digital volume pulse measurements was significantly reduced 6 hours after the EPA test meal, but not after the placebo meal. Vascular tone decreased at 6 hours in both groups, suggesting vasodilation, but did not differ between the two meals. Plasma 8-isoprostane F2α concentration, a marker of lipid peroxidation, increased after 6 hours in the EPA group, but the two groups did not differ significantly. Lack of group difference is likely attributable to the small number of participants. Total nitrate and nitrite, metabolites of nitric oxide, decreased in both groups compared with baseline values, but changes did not differ between the groups. There were no significant differences in blood pressure and heart rate either.
The reduced arterial stiffness observed with increased consumption of a high dose of n-3 LC-PUFAs—5 g of EPA—supports previous reports of improved endothelial function with n-3 LC-PUFAs (vasodilation, brachial artery dilation) in healthy individuals and patients with type 2 diabetes and hyperlipidemia. The marked increase in plasma 8-isoprostane F2α suggests increased lipid peroxidation not specific to EPA. Overall, the study suggests that consumption of EPA contributes to improved endothelial function during postprandial lipemia that may offset the potentially harmful effects of high-fat meals associated with impaired vascular activity.
SOURCE: Hall WL, Sanders KA, Sanders TAB, Chowienczyk PJ. A high-fat meal enriched with eicosapentaenoic acid reduces postprandial arterial stiffness measured by digital volume pulse analysis in healthy men. J Nutr 2008;138:287-291. [PubMed]