ndothelial dysfunction is characterised by a reduction in the synthesis of nitric oxide and a concomitant decrease in flow mediated dilation. This is thought to lead to increases in blood pressure, which is a risk factor for cardiovascular disease. Endothelial dysfunction is increasingly being linked to oxidative stress. Free radicals can block the production of nitric oxide because they inhibit the synthesising enzyme nitric oxide synthase. Foods that provide a high amount of antioxidants to the plasma are therefore of interest to nutritional scientists with regard endothelial dysfunction. Evidence to date suggests that a number of foods, known to be high in antioxidant, are beneficial at increasing flow mediated dilation through their modulating effect on nitric oxide synthase. Olives and grapes are two foods that have been shown to improve flow mediated dilation and to reduce blood pressure in humans. Recent evidence also suggests that walnut may be beneficial.
For example, in one study published in the Journal of the American College of Nutrition in 20121 investigated the effects of an eight week ad libitum walnut enriched diet or an ad libitum walnut free diet on the changes in flow mediated dilation of the brachial artery. The enriched diet contained 56 g of walnuts per day, and the study was designed with a crossover so that the 46 overweight subjects consumed both diets with a 4 week washout period in between. The results showed that flow mediated dilation improved significantly in the subjects consuming the walnut enriched diets when compared to the control diet. There were also trends to improved blood pressure measurements in the walnut group. Walnuts contain ellagic acid, a bioavailable polyphenol that may account for the positive effects on endothelial function. However, they also contain α-linolenic acid (ALA, C18:3 (n-3)), which may also have beneficial cardiovascular effects.