Abstract 140: The Effects of Modest Dietary Salt Reduction on Vascular Function and Blood Pressure in Overweight and Obese Adults

Abstract

Short term sodium restriction improves endothelial function as measured by flow-mediated dilatation (FMD), however the longer term effects of a modest reduction in dietary salt intake on vascular endothelial function in overweight and obese persons is unknown. Our objective was to determine the effects of a reduction in dietary sodium to 100mmol Na/day compared with 160mmol Na/day on measures of vascular function, and plasma and urinary nitrate/nitrite concentrations and 24hr ambulatory blood pressure in overweight and obese subjects. In a 6 week randomised cross-over trial of 100 Na mmol/day compared to 160mmol Na/day (achieved by giving sodium tablets) overweight and obese subjects had measurements of flow-mediated dilatation (FMD), 24hr BP, augmentation index (AIx), pulse wave velocity (PWV) and plasma and urinary nitrate/nitrite concentrations at the end of each intervention. Twenty five overweight and obese subjects aged 57±7 years (BMI 31.58±3.93kg/m 2 ; SBP 128±11mmHg; DBP 76±5mmHg) completed the intervention. Urinary sodium decreased from 155±58mmol/24hr to 113±45mmol/24hr (p=0.002). Weight and 24hr urinary potassium excretion were not different between interventions (p>0.05) as planned. Following sodium reduction there was a significant improvement in FMD from 3.54±2.83% to 5.63±2.79% (p<0.001). Daytime DBP decreased from 77±6mmHg to 75±7mmHg (p=0.087) with sodium reduction. Endothelium-independent vasodilatation, AIx, PWV and plasma and urinary nitrate/nitrite concentration were not significantly different between treatments (p>0.05). Change in FMD was significantly related to the urinary sodium to creatinine ratio (R = -0.470 P=0.018). Modest sodium reduction has beneficial effects on vascular function in overweight and obese subjects but does not alter nitrate/nitrite concentration in the urine or plasma. Further work is needed to explore the mechanisms by which salt affects vascular function in overweight and obese adults.