1. Twenty-one normotensive subjects were studied to assess any possible benefits of moderate salt restriction and of high potassium intake in the prevention of hypertension in man.
2. The effects of salt reduction from 200 to 50 mmol/day and/or of an increase of potassium intake from 80 to 200 mmol/day over a 2 week period, on blood pressure, plasma noradrenaline, adrenaline, vasopressin, renin and aldosterone, were measured both at rest and after mental stress. The effects of graded infusion of noradrenaline on blood pressure and heart rate were also studied.
3. Salt restriction lessened the increase of blood pressure during noradrenaline infusion; the combination with high potassium intake also reduced the pressure rise after mental stress. There were no major changes in plasma levels of vasopressin and adrenaline. Plasma noradrenaline increased during the low sodium diet.
4. High potassium intake improved baroreceptor function as revealed by the greater decrease in heart rate for a given rise in pressure after noradrenaline infusion.
5. The results of this study are compatible with a protective effect of a practicable low sodium/high potassium diet on the development of human hypertension.