NEUROHORMONAL AND METABOLIC EFFECTS OF SEVERE AND MODERATE SALT RESTRICTION IN NONOBESE NORMOTENSIVE ADULTS

Objective: The effects of severe and moderate sodium restriction on bl ood 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 d iet of 85 or 200 mmol/day sodium for 4 weeks each in random order. Res ults: After severe salt restriction 19% of the subjects had a signific ant decline (salt-sensitive group), 15% showed a significant rise (cou nter-regulator group) and 66% exhibited no change in blood pressure (s alt-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 correctio n for haematocrit, only the changes in total and low-density lipoprote in-cholesterol remained significant. The rise in plasma renin activity during salt restriction was steeper in the counter-regulator group th an in the other groups, whereas the changes in plasma noradrenaline co ncentrations were similar in all groups. During moderate salt restrict ion, plasma renin activity and noradrenaline concentration were signif icantly increased, but serum lipid concentrations and blood pressure d id not change. Conclusion: In non-obese normotensive adults, severe an d moderate salt restriction stimulates neurohormonal activity. In cont rast to severe salt restriction, a moderate reduction in dietary salt intake does not influence blood lipids in normotensive subjects.