Beet the cold: The effect of acute and chronic beetroot juice supplementation on extremity rewarming, endothelial function and anti-inflammatory status in people with Raynaud's phenomenon: A pilot, double-blind, placebo controlled, randomised crossover trial

Raynaud's phenomenon is characterised by recurrent transient vasospasm of the digits and lower nitric oxide (NO) bioavailability in response to cold stimuli. We investigated whether nitrate-rich beetroot juice (BJ) supplementation would (i) promote NO-mediated vasodilation, (ii) increase cutaneous vascular conductance (CVC) and skin temperature (Tsk) following cold challenge and (iii) reduce inflammation in individuals with Raynaud's phenomenon. Twenty-three individuals with Raynaud's phenomenon attended 4 laboratory testing sessions, in a crossover design, following acute (acute-BJ) and chronic (chronic-BJ; 14 days) BJ and nitrate-depleted BJ (acute-PL and chronic-PL) supplementation. At each visit, peripheral Tsk and CVC were measured during hand and foot cold sensitivity testing. This involved 2 minutes cooling in 15°C water, followed by 10 minutes rewarming in 30°C air and during transdermal delivery of acetylcholine and sodium nitroprusside on the forearm, finger and foot. Markers of inflammation were also measured. Plasma [nitrite] increased in the BJ conditions (P < 0.01). Plasma [interleukin-10] was greater, forearm endothelial function was improved. Following chronic-BJ and chronic-PL supplementation, thumb CVC was increased (P < 0.05) during and after a cold sensitivity testing, with no changes in Tsk between conditions (P > 0.05). Both acute-BJ and chronic-BJ supplementation can improve anti-inflammatory status, and endothelial function in individuals with Raynaud's phenomenon. CVC following a cold stimulus increased following chronic-BJ and chronic-PL supplementation, with no effect on Tsk.