(11-03-10) Dietary salt loading impairs arterial vascular reactivity1,2,3

Alwyn S Todd, Robert J MacGinley, John BW Schollum, Richard J Johnson, Sheila M Williams, Wayne HF Sutherland, Jim I Mann and Robert J Walker

1 From the Departments of Medical & Surgical Sciences (AST JBWS WHFS JIMRJW)PreventiveSocial Medicine (SMW) University of Otago Dunedin New Zealand; the Deakin University Medical School Deakin University Geelong Australia (RJM);the Division of Renal DiseasesHypertension University of Colorado Denver CO (RJJ).
2 Supported by the National Heart Foundation of New Zealand and the Otago Medical Research Foundation. AST was the recipient of a Neige Todhunter Award from the New Zealand Dietetic Association and a Unilever Research Scholarship.
3 Address correspondence to RJ Walker, Department of Medical & Surgical Sciences, University of Otago, Great King Street, PO Box 913, Dunedin 9015, New Zealand. E-mail: [email protected] .
Background: Studies of sodium have shown improvements in vascular function and blood pressure (BP). The effect of chronic sodium loading from a low-sodium diet to a Western diet on vascular function and BP has been less well studied.
Objective: The objective was to examine the effects of dietary salt intake on vascular function and BP.
Design: Thirty-five hypertensive volunteers met the inclusion criteria. After a 2-wk run-in with a low-sodium diet (60 mmol/d), the participants maintained their diets and were randomly assigned to receive sequentially 1 of 3 interventions for 4 wk, with a 2-wk washout between interventions: sodium-free tomato juice (A), tomato juice containing 90 mmol Na (B), and tomato juice containing 140 mmol Na (C). The outcomes were changes in pulse wave velocity (PWV), systolic BP (SBP), and diastolic BP (DBP).
Results: The difference in PWV between interventions B and A was 0.39 m/s (95% CI: 0.18, 0.60 m/s; P 0.001) and between C and A was 0.35 m/s (95% CI: 0.13, 0.57 m/s; P 0.01). Differences in SBP and DBP between interventions B and A were 4.4 mm Hg (95% CI: 1.2, 7.8 mm Hg; P 0.01) and 2.4 mm Hg (95% CI: 0.8, 4.1 mm Hg; P 0.001), respectively, and between interventions C and A were 5.6 mm Hg (95% CI: 2.7, 8.4 mm Hg; P 0.01) and 3.3 mm Hg (95% CI: 1.5, 5.0 mm Hg; P 0.001), respectively. Changes in PWV correlated with changes in SBP (r = 0.52) and DBP (r = 0.58).
Conclusions: Dietary salt loading produced significant increases in PWV and BP in hypertensive volunteers. Correlations between BP and PWV suggest that salt loading may have a BP-independent effect on vascular wall function. This further supports the importance of dietary sodium restriction in the management of hypertension. This trial was registered with the Australian and New Zealand Clinical Trials Registry as ACTRN12609000161224.

Source: Am J Clin Nutr 91: 557-564, 2010

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