Approximately one in three adult Americans have high blood pressure or hypertension. Hypertension is a risk factor for heart disease, stroke and kidney disease. Although some sodium in your diet is necessary for proper health, too much can increase your risk for high blood pressure, especially in individuals who are salt-sensitive.

Sodium attracts and retains water. Under normal conditions, sodium helps to regulate the fluid in your body, including blood volume, which effects your blood pressure. Too much salt can increase your blood volume and, therefore, your blood pressure. A sensitivity to salt means that you experience these effects to a greater degree than the general population. Fortunately, exercise can help reduce your sensitivity to salt according to research findings presented last week during the American Heart Association's Nutrition, Physical Activity and Metabolism/Cardiovascular Disease Epidemiology and Prevention 2011 Scientific Sessions.

The lead author of the study, Casey M. Rebholz, who is a medical student at the Tulane School of Medicine and doctoral student at the Tulane University School of Public Health & Tropical Medicine in New Orleans, studied 1,906 Han Chinese adults from the Genetic Epidemiology Network of Salt Sensitivity (GenSalt) project. The GenSalt project was designed to investigate the contributing factors to salt sensitivity, such as genetic and environmental factors. The subjects were placed on two one-week diets: a "low" sodium regimen (3,000 mg/day) and a "high" sodium regimen (18,000 mg/day). Their blood pressures were monitored during each testing week. Participants whose blood pressure rose more than 5 percent from the low-sodium diet to the high-sodium diet were labeled as having a high sensitivity to salt.

Subjects were further classified according to activity level. They were divided into four groups according to their responses to a physical activity questionnaire. These groups were: least activity; next-to-lowest activity; next-to-highest activity; and, most active group. The investigators found that a dose-response relationship existed between exercise and salt-sensitivity. That is, the more active the subject, the less likely he or she was to be classified as salt sensitive.

Investigators found that the least active group experienced a 5.27 mm HG rise in blood pressure from the low-sodium regimen to the high-sodium regimen, where as the most active group only experienced a rise of 3.88 mm HG between the two testing conditions. When compared to the least active group, the odds of being salt-sensitive for the most active group fell by 38 percent.

The authors concluded that "the more physically active you are, the less your blood pressure rises in response to a high-salt diet." They also noted that further testing is needed in other populations, but they suspect the results will be similar.

The American Heart Association recommends limiting your daily sodium intake to no more than 1,500 mg/day.

Note: Before beginning an exercise program or increasing the intensity level of a current routine, a physician's approval should be obtained, especially for older adults and those at risk for or who currently have chronic health conditions.

References
EurekAlert!; "Physical Activity Decreases Salt's Effect on Blood Pressure"; Public Press Release Date: 23-March-2011

Mayo Clinic: Sodium--How to Tame Your Salt Habit Now