Influence of acute beetroot juice supplementation on cold-induced vasodilation and fingertip rewarming.

Abstract

Vasoactive ingredients in beetroot (BR) such as nitrate are known to induce vasodilation in temperate conditions. This study investigated the effect of BR ingestion on cold induced vasodilation (CIVD) and rewarming of finger skin temperature (Tfing) during and after hand immersion in cold water. Twenty healthy males (mean ± SD; age 22.2 ± 0.7 years, height 172.6 ± 6.0cm, body mass 61.3 ± 11.7kg) repeated a hand cold water immersion test twice with prior BR or water beverage ingestion (randomised order). They rested for 2h in thermoneutral conditions (27°C, 40% relative humidity) after consuming the beverage, then immersed their non-dominant hand in 8°C water for 30min. They then rewarmed their hand in the ambient air for 20min. Skin temperature at seven body sites, Tfing, finger skin blood flow (SkBFfing), and blood pressure were measured. During hand immersion parameters of CIVD (Tfing and SkBFfing) were not different between BR and water conditions although skin temperature gradient from proximal to distal body sites was significantly smaller with BR (P < 0.05). During rewarming, SkBFfing and cutaneous vascular conductance were significantly higher with BR than with water (P < 0.05). The rewarming speed in Tfing and SkBFfing was significantly faster with BR at 15- (BR 1.24 ± 0.22 vs water 1.11 ± 0.26°C/min) and 20-min rewarming (P < 0.05). Additionally, individuals with slower rewarming speed with water demonstrated accelerated rewarming with BR supplementation. BR accelerated rewarming in Tfing and SkBFfing after local cold stimulus, whereas, CIVD response during hand cold immersion was not affected by BR ingestion.