A conjecture about the prevalence of essential hypertension and its high incidence in the black.

The high incidence in certain racial groups of essential hypertension is attributed to the advantage which this disease confers when the availability of sodium is deficient in the environment. This conjecture is supported by alterations in behaviour of sodium in the body economy of the hypertensive as evidenced by: the effects of sodium depletion on the blood pressure; the elevated sodium content of the tissues in the hypertensive; the reduced rate of sodium excretion in spontaneous and experimental hypertensive disease; the fact that hypertension can be induced in the offspring of rats subjected to a deficient sodium intake or to natriuretic drugs during pregnancy; the increased appetite for sodium observed in the hypertensive; and the effect of an increased sodium intake on the blood pressure. It is suggested that the substantial within-species variation in the incidence of essential hypertension reflects the availability of the sodium requirement of the individual suffering from the genetic mutation responsible for this disease.