Effects of dietary nitrate supplementation on the response to extremity cooling and endothelial function in individuals with cold sensitivity. A double blind, placebo controlled, crossover, randomised control trial.

Design: randomized, double-blind, cross-over, placebo-controlled trial. Participants: 13 cold-sensitive adults (4 women, 9 men); age 34.5 ± 13.2 years; height 1.77 ± 0.07 m; body mass 85.0 ± 15.9 kg; non-smokers; frequent exposure to cold environments.

Oral consumption of a single 140 mL beverage per visit: concentrated beetroot juice containing 11.9 mmol nitrate (nitrate supplementation) or nitrate-depleted beetroot juice (placebo) containing 0.02 mmol nitrate; consumed approximately 90 minutes before testing.

Plasma nitrite increased with nitrate supplementation compared with Placebo and Baseline (P<0.001). Resting blood pressure, skin rewarming rate, and endothelium-dependent vasodilation did not differ between conditions (P>0.05). Acute nitrate supplementation did not alter extremity rewarming, endothelial function, or blood pressure in cold-sensitive individuals after a local cold challenge. Authors conclude that acute inorganic nitrate via beetroot juice does not improve vascular function in this sub-population; chronic supplementation might hold potential, but was not demonstrated here.

Did not measure redox balance; small sample size with some missing data due to technical issues; acute, single-dose design; limited generalizability to chronic supplementation and to non-cold-sensitive populations.