Intro: Hypertension is a prominent risk factor for cardiovascular disease and arterial stiffness is a related predictor of both mortality and longitudinal onset of hypertension in normotensive individuals. Both vascular compliance and blood pressure have been shown to improve following dietary nitrate supplementation in some healthy and diseased individuals. Dietary nitrate supplementation increases plasma nitrite and may, therefore, enhance bioavailability of endothelium derived nitric oxide. Chronic increased flow mediated dilation (FMD) and reduction of pulse wave velocity (PWV) reduce a person’s long-term risk for developing endothelial dysfunction, atherosclerosis and hypertension.
Hypothesis: We hypothesized that an acute dose of dietary nitrate would improve FMD, decrease PWV and reduce central blood pressure (cBP) in healthy, young females.
Methods: Seven healthy, young (21 ± 2 years) females participated in a randomized, double blind, placebo controlled, crossover protocol. Participants had endothelial function measured via FMD, arterial stiffness via PWV and applanation tonometry, and cBP was determined non-invasively using pulse wave analysis following a 12-hour fasting period and 48-hour NIH approved low nitrate diet. Baseline values were measured the day before each treatment visit (placebo or nitrate-rich, separated by a 1-week washout period). Participants consumed either a placebo or nitrate-rich supplement (negligible and 6.2 mmol nitrate, respectively) 2 hours prior to their laboratory visit. Upon arrival, blood was drawn and participants assumed a supine position for 15 minutes. Then brachial artery FMD was assessed via high definition ultrasound imaging following 5 minutes of proximal forearm occlusion, followed by PWV and central blood pressure measurements.
Results: Plasma nitrite was elevated following consumption of the nitrate rich supplement compared to placebo (26.33 ± 15.76 and 1.18 ± 0.96 arbitrary units, respectively; p<0.05). However, there was no difference between nitrate rich and placebo treatments for endothelial function as measured by FMD (10.33 ± 1.82 and 9.11 ± 5.43%, respectively; p=0.70). No difference was present between nitrate and placebo groups for PWV (5.99 ± 0.85 and 6.16 ± 0.80 m/s, respectively; p=0.90), systolic cBP (101.57 ± 9.29 and 96.90 ± 20.95 mmHg, respectively; p=0.40) and diastolic cBP (72.57 ± 7.67 and 73.20 ± 5.01 mmHg, respectively; p=0.97).
Conclusion: While a single dose of dietary nitrate does increase plasma nitrite, supplementation has minimal effects on FMD, PWV and cBP in young healthy females. Future research should examine longer duration supplementation protocols as well as the changes in vascular health of patients with known disease such as hypertension or peripheral artery disease.