Critical review of studies on salt and hypertension.

The importance of salt intake for blood pressure homeostasis is critically surveyed, from a physiological point of view. Both ordinary rats and the great majority of mankind appear to tolerate quite a wide range of intakes at only minor effects on blood pressure. Further, both species seem to have their "physiological setpoints" at closely similar levels, if only differences in body size and metabolic rate are considered. No doubt risks increase towards both end of the intake spectrum, where those at low intakes have been much neglected though they were recently explored in rats, also concerning the mechanisms involved. In both species, however, genetic differences affect also the salt balance, where a minority of human beings shows various degrees of "salt sensitivity", apparently more often so in e.g. American blacks than in whites. This may well reflect a relative dominance for mechanisms favouring salt conservation which, in some environments, seems to be of vital importance. However, when such individuals are confronted with the more liberal salt consumption in modern society, their particular setting of salt balance may rather serve to aggravate or even precipitate hypertension, especially when other predisposing elements are at hand. It is tentatively discussed how to best handle such situations without interfering too much with consumption habits and "quality of life" for the great majority of "salt resistants"; further that more research should be directed towards identification and further analyses of salt sensitive subgroups.