Dietary Nitrate Supplementation Improves Vascular Function Similarly In Older Men And Women

Aging is accompanied by a reduced nitric oxide bioavailability and overall impaired vascular function. Dietary nitrate supplementation increases nitric oxide bioavailability and improves vascular function in older adults. However, it is unknown if there is a sex-dependent effect of dietary nitrate supplementation on vascular function in older adults. PURPOSE: Determine if there are sex-dependent effects of dietary nitrate supplementation on vascular function in older adults. METHODS: Ten older adults [5 men (70 ± 7 yr); 5 women (70 ± 7 yr)] participated in a double-blind, placebo-controlled, crossover study. In a quasi-randomized, counterbalanced order, participants were assigned to a 3-day nitrate supplementation (nitrate-rich beetroot juice, 12.9 mmol, 140 ml per day) and a placebo supplementation (nitrate-depleted beetroot juice, 0.05 mmol, 140 ml per day). Following supplementation, participants reported to the lab for measures of vascular function in the lower limb. Doppler ultrasonography was used to measure flow-mediated dilation (FMD) and post-occlusive reactive hyperemia of the superficial femoral artery in response to a 5-min bout of leg ischemia (250 mmHg). Post-occlusive reactive hyperemia was normalized to thigh lean mass obtained from a DXA scan. RESULTS: FMD was greater following nitrate supplementation (2.09 ± 1.38%) compared to the placebo supplementation (0.83 ± 1.26%) (p = 0.03, n2p = 0.48). FMD did not differ between sexes (p = 0.19, n2p = 0.21) and there was no sex-dependent effect of nitrate supplementation on FMD (condition x sex interaction effect; p = 0.77, n2p = 0.01). Peak post-occlusive reactive hyperemia did not differ between nitrate (235 ± 49 ml/min/kg) and placebo (247 ± 67 ml/min/kg) supplementations (p = 0.26, n2p = 0.21) nor between men and women (p = 0.76, n2p = 0.02). Similarly, there was no sex-dependent effect of nitrate supplementation on peak post-occlusive reactive hyperemia (condition x sex interaction effect; p = 0.23, n2p = 0.23). CONCLUSION: These preliminary results suggest that dietary nitrate supplementation in the form of beetroot juice improves FMD similarly in older men and women. NIH predoctoral TL1 (2TL1R001437) to BEA, AHA postdoctoral fellowship (909084) to TJF, NIA R01 (AG048262) to SKH & CWS.