The more you exercise, the less your blood pressure rises after scarfing down a high-salt diet, according to new research presented recently at the American Heart Association’s Nutrition, Physical Activity and Metabolism/Cardiovascular Disease Epidemiology and Prevention 2011 Scientific Sessions.
Researchers put volunteers who had normal blood pressure on two one-week diets: low sodium (3,000 mg/day) and high sodium (18,000 mg/day). In the study, subjects whose average systolic blood pressure—the top number in the reading—increased 5 percent after switching from the low-sodium to the high-sodium diet were labeled salt-sensitive.
But when researchers took physical activity into account, they noticed that exercise blunted the harmful effects of salt. The most active volunteers had 38 percent lower odds of being salt sensitive compared to sedentary subjects. “We found the more activity, the better response to salt,” said lead study author Casey M. Rebholz, M.P.H., 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.
Scientists haven’t yet figured out why getting sweaty can counteract the effects of a salty diet. It could be because exercise lowers cholesterol and blood pressure, explains Aryan Aiyer, M.D., director of the heart center at Magee-Womens Hospital at the University of Pittsburgh Medical Center. Other possibilities: Exercise might enhance sodium excretion from the kidneys, or maybe heart-pumping workouts help blood vessels dilate and become more elastic, Aiyer says.
If you’re reasonably healthy, exercise regularly, and have normal blood pressure, don’t worry about cutting down on salt, Aiyer says. To safeguard your heart, watch your weight: Overweight and obesity are major, often-overlooked risk factors for high blood pressure.