PP.31.13

Abstract

Objective: Blood nitrate/nitrite indicate nitric oxide (NO) bioavailability and levels are typically lower in hypertensives compared to matched controls. Dietary nitrate has recently been shown to increase plasma nitrate/nitrite and decrease BP in multiple populations, including normotensives, subjects with peripheral vascular disease or COPD and recently in both treated and untreated hypertensives. The antihypertensive effect of dietary nitrate appears attributable to its in vivo reduction to nitrite and eventually NO. In this pilot study we wanted to assess the chronic effect of daily dietary nitrate supplementation among a group of hypertensives established on diverse antihypertensive regimens.Design and method: On day 0, eligible subjects wore an ambulatory BP monitor for 24 hours and fasting blood was taken. Subjects then consumed concentrated beetroot juice (140 ml), containing 12.9mmol nitrate for 14 consecutive days. On day 14 subjects consumed their last nitrate dose and again wore an ambulatory BP monitor for ∼24 hours and fasting blood was taken. Instructions not to alter activities which may affect NO kinetics was provided. Results: We recruited 21 subjects on anti-hypertensive treatment. Table 1 displays baseline demographics and changes in BP variables following nitrate supplementation. Despite significant increases in both serum nitrate and nitrite with nitrate supplementation, there was no overall effect on BP variables and a trend towards increase heart rate. In addition, we have commenced a double-blind, randomized, placebo-controlled, crossover trial to further examine the effect of dietary nitrate supplementation among treated hypertensives. Although we are still blinded to the treatment arms, interim analysis reveal conflicting responses in both arms. This trial will be completed in May 2015. Conclusions: Our results do not support the existing data suggesting an anti-hypertensive effect of dietary nitrate. Possible explanations may include co-existing morbidities, long standing hypertension with use of multiple anti-hypertensive agents and differing nitrate dosing. Further work is required to evaluate this therapeutic concept.