Connection Between Salt and Water Volume and in Blood Pressure Changes
Salt (sodium) is essential to our bodies. Normally the kidneys control the level of salt. If there is too much salt, the kidneys pass it into urine. But when our salt intake levels are very high, the kidneys cannot keep up and the salt ends up in our bloodstream. Salt attracts water. When there is too much salt in the blood, the salt draws more water into the blood. More water increases the volume of blood which raises blood pressure. Some people are more sensitive to salt than others. In some people too much salt will cause their blood pressures to rise, in others there will not be as large a change. About half of people are salt sensitive. African-Americans, the elderly and people with diabetes are more often salt sensitive. If you have high blood pressure, you can always benefits from decreasing your salt intake. Sodium has an important influence on blood pressure, but we are not sure exactly how it works. Since the systems that control blood pressure include dozens of complex vascular, neurological, and hormonal elements. Although the body can rid itself of excessive dietary sodium, it seems likely that eating salt expands your blood volume, at least to a subtle degree. In turn, the extra volume may signal your kidneys to trigger a cascade of hormonal and vascular effects that raise blood pressure. And some experts suspect that these hormones may have adverse effects on vascular health even if blood pressure remains stable. There is considerable evidence that salt is an important cause of hypertension. Primitive societies who ingest little or no salt have no hypertension. The blood pressure often falls toward normal. Unfortunately, when diets only moderately low in sodium have been given only minor reductions in blood pressure occur. Salt-induced hypertension has been produced in both man and experimental animals. The basic cause of the hypertension is an inability of the kidney to excrete the increased salt. Hemodynamic changes then occur which raise the blood pressure and so excrete the excess salt by pressure diuresis. The ability to excrete salt at normal levels of blood pressure varies from one individual to another. Those who require a higher than normal blood pressure are said to be “salt-sensitive”. Those who can excrete excess salt at normal levels of blood pressure are called “salt resistant”. The difference may be due to an inherited defect in the kidney to excrete salt. In any event, salt sensitive hypertension is effectively controlled with the administration of diuretics.