t is becoming increasingly evident that antioxidants are able to favourably modulate high blood pressure. In particular, plant antioxidants such as the polyphenol class of compounds are able to cause blood pressure changes by increasing flow mediated dilation. For example, in one study published in the Journal of Nutrition1, researchers investigated the effects of freeze-dried grape polyphenol powder or a placebo on the blood pressure, flow mediated vasodilation and nitric oxide production in men between 30 and 70 years with metabolic syndrome. The results showed that grape supplementation increased flow mediated vasodilation and decreased systolic blood pressure, when compared to the placebo. The changes in blood pressure were negatively associated with changes in nitric oxide concentrations, illustrating the role of nitric oxide in blood pressure regulation. Grape powder and grape supplements may therefore favourable affect endothelial function.
When oxidative stress is high, nitric oxide synthase levels fall and this reduces nitric oxide production in the endothelial lining of arteries. Because nitric oxide is responsible for causing vasodilation, oxidative stress therefore can lead to vasoconstriction and blood pressure increases. Polyphenols are thought to reduce blood pressure because they can act as antioxidants in humans. This ability to inhibit free radical production allows them to prevent decreases in nitric oxide synthase and thus modulate raised blood pressure. Consumption of the Mediterranean diet is associated with lower blood pressure, and evidence suggests that this might be due to the antioxidants in the diet. In particular, studies show that the antioxidants in extra virgin olive oil and red wine can act in a similar way to grape polyphenols and cause increases in flow mediated vasodilation (here).
