Effects of acute dietary nitrate supplementation on cold-induced vasodilation in healthy males.

Abstract

Cold-induced vasodilation (CIVD) is a paradoxical rise in blood flow to the digits that occur during prolonged cold exposure. CIVD is thought to occur through active vasodilation and/or sympathetic withdrawal, where nitric oxide (NO) may play a key role in mediating these mechanisms. Beetroot juice (BRJ) is high in dietary nitrate (NO3-) which undergoes sequential reduction to nitrite (NO2-) and subsequently NO. Using a double-blind, randomized, crossover design, we examined the effect of acute BRJ supplementation on the CIVD response in 10 healthy males. Participants had a resting blood pressure measurement taken prior to ingesting 140mL of nitrate-rich BRJ (13mmol NO3-) or a NO3--free placebo (PLA). After 2h, participants immersed their hand in neutral water (~ 35°C) for 10min of baseline before cold water immersion (~ 8°C) for 30min. Laser-Doppler fluxmetry and skin temperature were measured continuously on the digits. Compared to PLA (100 ± 3mmHg), acute BRJ supplementation significantly reduced mean arterial pressure at -30min (96 ± 2mmHg; p = 0.007) and 0min (94 ± 2mmHg; p = 0.008). Acute BRJ supplementation had no effect on Laser-Doppler fluxmetry during CIVD (expressed as cutaneous vascular conductance) measured as area under the curve (BRJ: 843 ± 148 PUmmHg-1s; PLA: 1086 ± 333 PUmmHg-1s), amplitude (BRJ: 0.60 ± 0.12 PUmmHg-1; PLA: 0.69 ± 0.14 PUmmHg-1), and duration (BRJ: 895 ± 60s; PLA: 894 ± 46s). Acute BRJ supplementation does not augment the CIVD response in healthy males.