Beet the cold: beetroot juice improves peripheral blood flow, endothelial function and anti-inflammatory status in individuals with Raynaud's phenomenon

Raynaud's phenomenon (RP) is characterised by recurrent transient peripheral vasospasm and lower nitric oxide (NO) bioavailability in the cold. We investigated the effect of nitrate-rich beetroot juice (BJ) supplementation on i) NO-mediated vasodilation, ii) cutaneous vascular conductance (CVC) and skin temperature (T_sk) following local cooling and iii) systemic anti-inflammatory status. Following baseline testing, twenty-three individuals with RP attended four times, in a double-blind, randomized crossover design, following acute and chronic (14 days) BJ and nitrate-depleted beetroot juice (NDBJ) supplementation. Peripheral T_sk and CVC were measured during and after mild hand and foot cooling, and during transdermal delivery of acetylcholine and sodium nitroprusside. Markers of anti-inflammatory status were also measured. Plasma [nitrite] was increased in the BJ conditions (P < 0.001). Compared to the baseline visit, thumb CVC was greater following chronic-BJ (Δ2.0 flux·mmHg^-1, P = 0.02) and chronic-NDBJ (Δ1.45 flux·mmHg-1, P = 0.01) supplementation; however, no changes in Tsk were observed (P > 0.05). Plasma [interleukin-10] was greater, pan endothelin and systolic and diastolic blood pressure (BP) were reduced, and forearm endothelial function was improved ,by both BR and NDBJ supplementation (P < 0.05). Acute and chronic BJ and NDBJ supplementation improved anti-inflammatory status, endothelial function and BP. CVC following cooling increased post chronic-BJ and chronic-NDBJ supplementation, but no effect on T_sk was observed.