More than 50 studies have investigated the effect of altered sodium intake on blood pressure. A regression line drawn through the change in blood pressure and change in sodium intake indicates that blood pressure alters about 10 mmHg (1 mmHg = 133.322 Pa) for every 100 mmol/day alteration in sodium intake, a change similar to that observed in between-population "studies." The studies that have failed to show a change in blood pressure have usually been in people with a blood pressure less than 130/90 mmHg. Normotensive people appear to tolerate a higher intake of sodium before blood pressure rises, but if increased sufficiently, blood pressure rises in most people. Sodium restriction reduces blood pressure in people with severe hypertension, moderate hypertension and mild hypertension. It may be the cause of blood pressure increase associated with age and the reason for the higher prevalence of hypertension and vascular disease in Western communities. Sodium restriction should be used to treat people with elevated blood pressure.