Neurohormonal and metabolic effects of severe and moderate salt restriction in non-obese normotensive adults

OBJECTIVE: The effects of severe and moderate sodium restriction on blood pressure, neurohormonal activity and serum lipids were studied in non-obese normotensive adults. METHODS: In the first part of the study, 163 subjects were randomly assigned to a diet of 20 or 300 mmol/day sodium for 1 week each. In the second part, 25 subjects were given a diet of 85 or 200 mmol/day sodium for 4 weeks each in random order. RESULTS: After severe salt restriction 19% of the subjects had a significant decline (salt-sensitive group), 15% showed a significant rise (counter-regulator group) and 66% exhibited no change in blood pressure (salt-resistant group). Severe sodium restriction increased plasma renin activity and noradrenaline concentration, as well as serum total and low-density lipoprotein-cholesterol and triglycerides. After correction for haematocrit, only the changes in total and low-density lipoprotein-cholesterol remained significant. The rise in plasma renin activity during salt restriction was steeper in the counter-regulator group than in the other groups, whereas the changes in plasma noradrenaline concentrations were similar in all groups. During moderate salt restriction, plasma renin activity and noradrenaline concentration were significantly increased, but serum lipid concentrations and blood pressure did not change. CONCLUSION: In non-obese normotensive adults, severe and moderate salt restriction stimulates neurohormonal activity. In contrast to severe salt restriction, a moderate reduction in dietary salt intake does not influence blood lipids in normotensive subjects.