Postprandial effects of a high salt meal on serum sodium, arterial stiffness, markers of nitric oxide production and markers of endothelial function

Abstract

Aim: The aim of the study was to determine if a high salt meal containing 65 mmol Na causes a rise in sodium concentrations and a reduction in plasma nitrate/nitrite concentrations (an index of nitric oxide production). Secondary aims were to determine the effects of a high salt meal on augmentation index (AIx) a measure of arterial stiffness and markers of endothelial function.

Methods and results: In a randomised cross-over study 16 healthy normotensive adults consumed a low sodium soup containing 5 mmol Na and a high sodium soup containing 65 mmol Na. Sodium, plasma nitrate/nitrite, endothelin-1 (ET-1), C-reactive protein (CRP), vasopressin (AVP) and atrial natriuretic peptide (ANP) concentrations before and every 30 min after the soup for 2 h. Blood pressure (BP) and AI were also measured at these time points. There were significant increases in serum sodium, osmolality and chloride in response to the high sodium meal. However plasma nitrate/nitrite concentrations were not different between meals (meal p = 0.812; time p = 0.45; meal × time interaction p = 0.50). Plasma ANP, AVP and ET-1 were not different between meals. AI was significantly increased following the high sodium meal (p = 0.02) but there was no effect on BP.

Conclusions: A meal containing 65 mmol Na increases serum sodium and arterial stiffness but does not alter postprandial nitrate/nitrite concentration in healthy normotensive individuals. Further research is needed to explore the mechanism by which salt affects vascular function in the postprandial period. This trial was registered with the Australian and New Zealand Clinical Trials Registry Unique Identifier: ACTRN12611000583943http://www.anzctr.org.au/trial_view.aspx?ID=343019.

Keywords: Arterial stiffness; Nitric oxide; Sodium.