Raynaud's phenomenon (RP) is characterized 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 1) NO-mediated vasodilation, 2) cutaneous vascular conductance (CVC) and skin temperature (Tsk) following local cooling, and 3) systemic anti-inflammatory status. Following baseline testing, 23 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 Tsk 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 concentration ([nitrite]) was increased in the BJ conditions (P < 0.001). Compared with the baseline visit, thumb CVC was greater following chronic-BJ (Δ2.0 flux/mmHg, P = 0.02) and chronic-NDBJ (Δ1.45 flux/mmHg, 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 BJ and NDBJ supplementation (P < 0.05). Acute and chronic BJ and NDBJ supplementation improved anti-inflammatory status, endothelial function and blood pressure (BP). CVC following cooling increased post chronic-BJ and chronic-NDBJ supplementation, but no effect on Tsk was observed. The key findings are that beetroot supplementation improves thumb blood flow, improves endothelial function and anti-inflammatory status, and reduces BP in people with Raynaud's.NEW & NOTEWORTHY This is the first study to examine the effect of dietary nitrate supplementation in individuals with Raynaud's phenomenon. The principal novel findings from this study were that both beetroot juice and nitrate-depleted beetroot juice 1) increased blood flow in the thumb following a cold challenge; 2) enhanced endothelium-dependent and -independent vasodilation in the forearm; 3) reduced systolic and diastolic blood pressure, and pan-endothelin concentration; and 4) improved inflammatory status in comparison to baseline.
Keywords: antioxidants; blood flow; nitrate.