• Hypertensive Disease
• Cardiology Clinical Trials
• Nutrition Physiology

• Hypertensive Disease
• Cardiology Clinical Trials
• Nutrition Physiology
• Cardiology

Mammals are unable to metabolize nitrate, but symbiotic bacteria on the dorsal tongue surface reduce dietary nitrate to nitrite, which is then converted to the potent vasodilator nitric oxide [Duncan C et al. Nat Med 1995]. Vikas Kapil, MD, PhD, William Harvey Research Institute, Queen Mary University, London, United Kingdom, presented results of The Chronic Effects of Beetroot Juice in Hypertensive Subjects study, which assessed whether a once-daily ingestion of dietary nitrate would exert a sustained effect on blood pressure (BP) in hypertensive patients [NCT01405898].

A total of 68 patients with stage 1 hypertension were enrolled in this randomized, double-blind, placebo-controlled trial. The patients were stratified according to whether they were treatment naïve or previously treated (not to target) for hypertension. Following a 2-week run-in period, the patients were randomized to a dietary supplement consisting of 250 mL/day of beetroot juice containing dietary nitrate (n=34) or to placebo consisting of nitrate-free beetroot juice (n=34) for 4 weeks.

The primary endpoint was change in clinic, ambulatory, and home BP. The secondary endpoints were pulse-wave velocity (PWV), endothelial function assessed by measurement of flow-mediated dilatation, and plasma nitrite and nitrate concentrations. Clinic BP was measured 3 times every 15 minutes for 1 hour. The second and third readings at each time point were averaged overall. Ambulatory BP was measured once every 20 minutes during the day and every 60 minutes during the night. Home BP was measured daily, in triplicate, with the second and third readings averaged.

Baseline characteristics were similar between the 2 treatment groups. Two patients in each arm dropped out of the study. Ingestion of dietary nitrate increased plasma nitrite by a mean ± SD of 0.52±0.37 mmol/L compared with a decrease of 0.01±0.16 mmol/L after ingestion of placebo (p<0.001). Plasma nitrate was also significantly increased after ingestion of dietary nitrate, as shown by an increase in plasma cyclic guanosine monophosphate of 2.52±3.30 compared with a decrease of 0.91±2.80 after ingestion of placebo.

Clinic systolic BP was significantly reduced by 8.7± 8.2 mm Hg after ingestion of nitrate compared with a reduction of 1.0±8.4 mm Hg after ingestion of placebo (p<0.001). Clinic diastolic BP was significantly reduced by 3.2±5.4 mm Hg after ingestion of nitrate compared with a reduction of 0.7±4.2 mm Hg after ingestion of placebo (p<0.050).

Ambulatory systolic BP was significantly reduced by 6.6±6.5 mm Hg after ingestion of nitrate compared with an increase of 0.8±4.9 after ingestion of placebo (p<0.001). Ambulatory diastolic BP was significantly reduced by 4.3±6.0 mm Hg after ingestion of nitrate compared with an increase of 0.9±3.8 mm Hg after ingestion of placebo (p<0.001). Patients in the dietary nitrate group versus those in the placebo group had significant reductions in home systolic (p=0.001) and diastolic (p=0.036) BP.

Ingestion of dietary nitrate versus placebo significantly improved PWV (+0.59±0.93 vs +0.01±1.11 m/s, p=0.031) and vessel dilatation (+0.9±1.3% vs +0.1±0.6%, p=0.005).

In this study, dietary nitrate lowered systolic and diastolic BP by about 8 and 4 mm Hg, respectively, improved endothelial function, and reduced arterial stiffness in hypertensive patients. According to Dr. Kapil, these results highlight the therapeutic potential of a high-nitrate diet for the prevention and treatment of hypertension. The results might also explain in part the cardioprotective effects of a fruit and vegetable rich diet.

• © 2014 MD Conference Express®