Cutting Salt Intake Restores Blood Vessel Health

Patients with moderate hypertension who were put on a sodium-restricted diet showed significant improvements in markers of vascular endothelial function, according to a new study.

Researchers at the University of Colorado (Boulder, USA) conducted a randomized, crossover study involving 17 volunteers (11 men and 6 women; mean age, 62 years) who completed a four-week period of both dietary sodium restriction (DSR) and normal sodium intake. Participants were first randomized to take slow-release salt pills daily, totaling 2,300 mg of sodium, intended to bring total daily intake to 3,600 mg, or matching placebo pills for 4 weeks. After a 2-week washout, participants were switched to the other pill type. Vascular endothelial function, as measured by endothelium-dependent dilation (EDD), nitric oxide (NO)/tetrahydrobiopterin (BH4) bioavailability, and oxidative stress-associated mechanisms were assessed following each condition.

The results showed that urinary sodium excretion was reduced by about 50%, and conduit and resistance artery EDD were 68% and 42% (respectively) higher following DSR. Low sodium markedly enhanced NO-mediated EDD without changing endothelial NO synthase expression/activation, and increased circulating superoxide dismutase activity. These effects were independent of the change in systolic blood pressure (SBP). Other subject characteristics, dietary factors, and endothelium-independent dilation were unchanged. The study was published ahead of print on October 25, 2012, in the Journal of the American College of Cardiology.

“Endothelial dysfunction seen when their diet contained roughly 3,600 mg/day of sodium was reversed when their intake was closer to 1,200 mg/day,” concluded lead author Douglas Seals, PhD, of the University of Colorado, in Boulder, and colleagues of the department of integrative physiology. “Our findings support the emerging concept that DSR induces ‘vascular protection’ beyond that attributable to its BP-lowering effects.”

Vascular endothelial dysfunction develops with advancing age and elevated SBP, contributing to increased cardiovascular risk. DSR lowers BP, but its effect on vascular endothelial function and the mechanisms involved are largely unknown. According to the study, the effect appears to be mediated by increasing the bioavailability of NO and BH4, and by reducing oxidative stress.

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