Influence of dietary inorganic nitrate on blood pressure and vascular function in hypertension: prospective implications for adjunctive treatment

Dietary inorganic nitrate (nitrate) is a promising adjunctive treatment to reduce blood pressure and improve vascular function in hypertension. However, it remains unknown if the efficacy of nitrate is dependent upon an elevated blood pressure or altered by medication in patients with hypertension. Therefore, blood pressure and vascular function, measured by passive leg movement (PLM) and flow-mediated dilation (FMD), were assessed following 3 days of placebo (nitrate-free beetroot juice) and nitrate (nitrate-rich beetroot juice) administration in 13 patients (age: 53 +/- 12 yr) with hypertension taking antihypertensive medications (study 1) and in 14 patients (49 +/- 13 yr) with hypertension not taking antihypertensive medications (study 2). In study 1, plasma nitrite concentration was greater for nitrate than placebo (341 +/- 118 vs. 308 +/- 123 nmol/L, P < 0.05), yet blood pressure and vascular function were unaltered. In study 2, plasma nitrite concentration was greater for nitrate than placebo (340 +/- 102 vs. 295 +/- 93 nmol/L, P +/- 0.01). Systolic (136 +/- 16 vs. 141 +/- 19 mmHg), diastolic (84 +/- 13 vs. 88 +/- 12 mmHg), and mean (101 +/- 12 vs. 106 +/- 13 mmHg) blood pressures were lower (P < 0.05), whereas the PLM change in leg vascular conductance (6.0 +/- 3.0 vs. 5.1 +/- 2.6 mL.min(-1).mmHg(-1)) and FMD (6.1 +/- 2.4% vs. 4.1 +/- 2.7%) were greater (P < 0.05) for nitrate than placebo. The changes in systolic blood pressure (r = -0.60) and FMD (r = -0.48) induced by nitrate were inversely correlated (P < 0.05) to the respective baseline values obtained in the placebo condition. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive medication status, per se. NEW & NOTEWORTHY Dietary nitrate (nitrate) is a promising intervention to improve blood pressure and vascular function in hypertension. We demonstrate that these beneficial effects of nitrate are inversely related to the baseline value in a continuous manner with no distinction between antihypertensive medication status. Thus, the efficacy of nitrate to improve blood pressure and vascular function in hypertension appears to be dependent on the degree of blood pressure elevation and vascular dysfunction and not antihypertensive mediation status.