Abstract
BACKGROUND/OBJECTIVES: To compare the effects of supplemental inorganic nitrate (NO(3)) on microvascular endothelial function and blood pressure in younger vs. older participants. SUBJECTS/METHODS: 25 individuals participated in a double-blind, randomised, placebo-controlled crossover pilot study. Participants were stratified by age (18-35 and ≥55 years) and consumed a single dose beetroot juice (providing 6.4 mmol NO(3)) or NO(3)-depleted beetroot juice. Blood pressure, microvascular function (via Laser Doppler Flowmetry; LDF) and urinary NO(3) were assessed, and the effects of NO(3) supplementation on cardiovascular parameters were compared between participants and conditions using mixed-design ANOVA. RESULTS: Treatments and methods were well tolerated, and no adverse events were reported. Urinary NO(3) increased 3 h following ingestion in both groups, (P = 0.02). Levels remained elevated at 24 h post consumption in younger participants only (P = 0.02). Beetroot juice had no effect on blood pressure in either group nor on microcirculatory endothelial function. CONCLUSIONS: Beetroot juice had no effect on blood pressure or microvascular endothelial function in young and older individuals. Dosage and timing regimens for supplemental beetroot juice should be avenues for further inquiry.