Acute Dietary Nitrate Supplementation Improves Flow Mediated Dilatation of the Superficial Femoral Artery in Healthy Older Males

Aging is often associated with reduced leg blood flow, increased arterial stiffness, and endothelial dysfunction, all of which are related to declining nitric oxide (NO) bioavailability. Flow mediated dilatation (FMD) and passive leg movement (PLM) hyperaemia are two techniques used to measure NO-dependent vascular function. We hypothesised that acute dietary nitrate (NO₃⁻) supplementation would improve NO bioavailability, leg FMD, and PLM hyperaemia. Fifteen healthy older men (69 ± 4 years) attended two experiment sessions and consumed either 140 mL of concentrated beetroot juice (800 mg NO₃⁻) or placebo (NO₃⁻-depleted beetroot juice) in a randomised, double blind, cross-over design study. Plasma nitrite (NO₂⁻) and NO₃⁻, blood pressure (BP), augmentation index (AIx75), pulse wave velocity (PWV), FMD of the superficial femoral artery, and PLM hyperaemia were measured immediately before and 2.5 h after consuming NO₃⁻ and placebo. Placebo had no effect but NO₃⁻ led to an 8.6-fold increase in plasma NO₂⁻, which was accompanied by an increase in FMD (NO₃⁻: +1.18 ± 0.94% vs. placebo: 0.23 ± 1.13%, p = 0.002), and a reduction in AIx75 (NO₃⁻: −8.7 ± 11.6% vs. placebo: −4.6 ± 5.5%, p = 0.027). PLM hyperaemia, BP, and PWV were unchanged during both trials. This study showed that a dose of dietary NO₃⁻ improved NO bioavailability and enhanced endothelial function as measured by femoral artery FMD. These findings provide insight into the specific central and peripheral vascular responses to dietary NO₃⁻ supplementation in older adults.