A high salt meal does not impair cerebrovascular reactivity in healthy young adults

A high sodium (Na⁺) meal impairs peripheral vascular function. In rodents, chronic high dietary Na⁺ impairs cerebral vascular function, and in humans, habitual high dietary Na⁺ is associated with increased stroke risk. However, the effects of acute high dietary Na⁺ on the cerebral vasculature in humans are unknown. The purpose of this study was to determine if acute high dietary Na⁺ impairs cerebrovascular reactivity in healthy adults. Thirty-seven participants (20F/17M; 25 ± 5 years; blood pressure [BP]: 107 ± 9/61 ± 6 mm Hg) participated in this randomized, cross-over study. Participants were given a low Na⁺ meal (LSM; 138 mg Na⁺) and a high Na⁺ meal (HSM; 1,495 mg Na⁺) separated by ≥ one week. Serum Na⁺, beat-to-beat BP, middle cerebral artery velocity (transcranial Doppler), and end-tidal carbon dioxide (P_ETCO₂) were measured pre- (baseline) and 60 min post-prandial. Cerebrovascular reactivity was assessed by determining the percent change in middle cerebral artery velocity to hypercapnia (via 8% CO₂, 21% oxygen, balance nitrogen) and hypocapnia (via mild hyperventilation). Peripheral vascular function was measured using brachial artery flow-mediated dilation (FMD). Changes in serum Na⁺ were greater following the HSM (HSM: Δ1.6 ± 1.2 mmol/L vs. LSM: Δ0.7 ± 1.2 mmol/L, p <.01). Cerebrovascular reactivity to hypercapnia (meal effect: p =.41) and to hypocapnia (meal effect: p =.65) were not affected by the HSM. Contrary with previous findings, FMD was not reduced following the HSM (meal effect: p =.74). These data suggest that a single high Na⁺ meal does not acutely impair cerebrovascular reactivity, and suggests that despite prior findings, a single high Na⁺ meal does not impair peripheral vascular function in healthy adults.