People in isolated rain-forest communities tend to live on a largely vegetarian diet, and they eat little salt  Few of them suffer from high blood pressure, and their blood pressure does not tend to increase with age, as is common in industrialized countries  Such people often do develop high blood pressure when they move to cities and adopt high-salt diets
Though suggestive, these facts do not establish salt as the culprit in high blood pressure, however, because
there are changes in other aspects of diet when such people move to the city