DIETARY TREATMENT OF HYPERTENSION. II. SODIUM DEPLETION AS RELATED TO THE THERAPEUTIC EFFECT 1

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Abstract
Restriction of dietary Na to 7 meq./day caused statistically significant reductions in the avg. blood pressures (B. P.) of 5 patients with uncomplicated hypertension. These reductions were due to the limitation of dietary Na, since no B. P. changes had been observed during a preliminary equilibration stage of 2-4 months'' duration in which the low-Na diet was supplemented with salt tablets (10 g./ day). Weight losses and large variations in the intakes of protein and of water during this time had no significant effects on the blood pressure. Following withdrawal of the salt supplement, the patients lost 14-20% of their exchangeable Na during the 1st month of adaptation and then apparently attained balance. On readministration of salt 10 weeks later, the patients reaccumulated Na approx. to the control level. On the supposition that the lost Na was derived from extracellular fluid, the losses of body water appeared to be disproportionately small. The interpretation offered was that the surplus extracelular water, not excreted with its Na, shifted into an intracellular position and thereby increased cellular hydration by about 5%. The reverse effects were observed following readmin-istration of salt. The hypothesis was advanced that the low Na diet exerted its beneficial effect in the hypertensive patients by causing an increase in cellular hydration.