Introduction Nitric oxide (NO) is a systemic- and pulmonary-vasodilator. NO synthesis in vivo can be facilitated by reduction of dietary nitrate (NO₃) to NO independent of NO synthase in a process that is upregulated under certain clinical conditions, possibly providing therapeutic effect. Multiple cardiorespiratory pathologies are associated with perturbations in NO, including uncontrolled hypertension (HTN) and obstructive sleep apnoea syndrome (OSAS). To extend findings from our preliminary studies, we hypothesised that dietary NO₃ may have utility in cardiorespiratory disorders associated with decreased NO bioavailability and elevated blood pressure (BP).

Methods We conducted 2 separate double-blind, randomised, placebo-controlled, crossover trials of daily NO₃supplementation as concentrated beetroot juice compared to matching nitrate-depleted beetroot juice placebo (PL) for 7 d among a group of well-characterised, uncontrolled hypertensives and subjects with newly diagnosed OSAS on ambulatory BP and biochemical parameters.

Results We recruited 20 uncontrolled hypertensives (mean age = 63 y, mean BMI = 31 kg/m², mean no. of antihypertensives = 2) as well as 12 adults with severe OSAS (mean apnoea-hypnoea index = 74, mean age = 52 y, mean BMI = 31 kg/m²). Assessments were conducted on three occasions, baseline (day 1), midpoint, (day 8) and endpoint (day 15) – before and after each intervention period and included plasma nitrate as well as 24 h ambulatory blood pressure monitoring (Table 1).

Conclusions Daily dietary nitrate was well-tolerated, safe and led to increased plasma NO metabolites and decreased BP profiles in uncontrolled hypertensives and OSAS. Dietary nitrate has potential as a novel therapeutic, adjunct strategy in difficult to treat BP. Considering the low cost and safety profile of dietary nitrate containing foods and supplements, this concept appears promising as an adjunct therapeutic strategy for cardiovascular diseases.