Short-term effects of nitrate-rich green leafy vegetables on blood pressure and arterial stiffness in individuals with high-normal blood pressure.

Evidence for a beneficial effect of dietary nitrate, through the nitrate-nitrite-NO pathway, on measures of cardiovascular function in healthy individuals is accumulating. It is less clear whether increased dietary nitrate intake from green leafy vegetables would have similar beneficial vascular effects in those at increased risk of developing hypertension. Our aim was to assess the effects of short term regular consumption of increased nitrate from green leafy vegetables on blood pressure and arterial stiffness in individuals with high-normal blood pressure. Thirty eight men and women aged 30-70 years with systolic blood pressure 120 to 139mmHg were recruited to a randomised controlled cross-over trial. The effects of a 7 day high nitrate diet intervention (increased nitrate intake by at least 300mg/day from green leafy vegetables) were compared to a 7 day low nitrate diet intervention. Outcome measures included pre and post salivary and plasma nitrate and nitrite concentrations, ambulatory, home and office blood pressure, augmentation index and carotid-femoral pulse wave velocity. The high nitrate diet intervention resulted in at least a fourfold increase in salivary and plasma nitrate and nitrite (P<0.001). Ambulatory, home and office blood pressure and arterial stiffness were not different between the high nitrate diet and the low nitrate diet. Increasing dietary nitrate intake in those with high normal blood pressure may not be an effective short-term strategy to lower blood pressure in those at increased risk of hypertension.