The salt epidemic: old and new concerns.

Salt is the most suspected environmental factor which may influence arterial pressure. The recent demonstration that in the chimpanzee there is a strict dose-response relationship between salt added to food and arterial pressure and that the large majority of these animals are "salt-sensitive" is solid proof that salt has a central importance in arterial hypertension. The behavioral complexity of mankind is such that the issue of salt sensitivity is very difficult to study in man. This is probably the main reason why all attempts to validate the arterial pressure response to tests of salt sensitivity based on changes in salt intake have produced negative or inconclusive results. However our inability to reliably identify salt-sensitive individuals in no way implies that the pressor effect of salt is evenly distributed in the population or that it is intrinsically so variable that the scientific efforts aimed at defining its nature are bound to fail. We envisage that in the near future the individual "salt-sensitive risk profile" will be calculated on the basis of new scientific knowledge about hypertension genes and environmental risk factors influencing the pressor response to salt. The link between target organ damage and salt is even stronger than that between arterial pressure and salt. Left ventricular mass is closely related to salt intake. In the kidney there is evidence that high salt intake induces hyperfiltration and raises glomerular pressure. Of note the damaging potential of salt to the heart and the kidney seems to be largely independent of the ongoing arterial pressure response. A widespread reduction in salt intake at population level might in theory produce major health benefits but it seems unlikely that major public health actions will be undertaken in the near future.