Metabolic and orthostatic blood pressure responses to a low-sodium diet in elderly hypertensives
In view of the concern regarding the potential risks and benefits of sodium restriction, the effect on biochemical and orthostatic responses from a moderate reduction in sodium intake in elderly persons that is sufficient to lower systolic blood pressure (SBP) was examined. Seventeen hypertensive subjects aged 65–79 years entered a double-blind randomized placebo controlled cross-over trial of a low sodium diet plus placebo tablets vs a low sodium diet plus sodium tablets (80 mmols/day) each for 5 weeks. At the end of high and low sodium periods, two 24-h urine collections and venous blood samples were undertaken and supine and standing BPs were recorded. On the low compared to the high sodium phase (urinary sodium excretion 95 ± 36 vs 174 ± 40 mmols/24-h, respectively), clinic supine SBP fell by 8 mm Hg (95% CI: 1–15 mm Hg, P < 0.05) and diastolic bp (dbp) by 1 mm hg (ci: −3 to 5 mm hg); there was no change in total ldl- and hdl-cholesterol and triglyceride levels, serum calcium, phosphate, parathyroid hormone, glucose, creatinine clearance or urinary albumin excretion rate. serum urate was significantly higher during the low compared to high sodium intake (304 ± 56 vs 277 ± 44  μ mols/l). Orthostatic BP responses during the high and low sodium intakes were unchanged. In summary, after 5 weeks of moderate sodium restriction no adverse effects other than an increase in serum urate was seen in elderly hypertensive persons.