Acute ingestion of beetroot juice increases exhaled nitric oxide in healthy individuals

BACKGROUND AND OBJECTIVE: Nitric oxide (NO) plays an important role in the airways’ innate immune response, and the fraction of exhaled NO at a flow rate of 50mL per second (F(E)NO(50)) has been utilized to capture NO. Deficits in NO are linked to loss of bronchoprotective effects in airway challenges and predict symptoms of respiratory infection. While beetroot juice supplements have been proposed to enhance exercise performance by increasing dietary nitrate consumption, few studies have examined the impact of beetroot juice or nitrate supplementation on airway NO in contexts beyond an exercise challenge, which we know influences F(E)NO(50). METHODS: We therefore examined the influence of a beetroot juice supplement on F(E)NO(50) in healthy males and females (n = 38) during periods of rest and in normoxic conditions. F(E)NO(50), heart rate, blood pressure, and state affect were measured at baseline, 45 minutes, and 90 minutes following ingestion of 70ml beetroot juice (6.5 mmol nitrate). Identical procedures were followed with ingestion of 70ml of water on a control day. RESULTS: After beetroot consumption, average values of the natural log of F(E)NO(50) (lnF(E)NO(50)) increased by 21.3% (Cohen’s d = 1.54, p < .001) 45 minutes after consumption and by 20.3% (Cohen’s d = 1.45, p < .001) 90 min after consumption. On the other hand, only very small increases in F(E)NO(50) were observed after consumption of the control liquid (less than 1% increase). A small subset (n = 4) of participants completed an extended protocol lasting over 3 hours, where elevated levels of F(E)NO(50) persisted. No significant changes in cardiovascular measures were observed with this small single dose of beetroot juice. CONCLUSION: As NO serves a key role in innate immunity, future research is needed to explore the potential clinical utility of beetroot and dietary nitrate to elevate F(E)NO(50) and prevent respiratory infection.