Health Discovery: Salt’s Effect on Hypertension

STUDY FINDINGS
• Cutting back salt consumption by only a third is all it takes to make a potentially big difference in your health and, at the same time, help protect your kidneys and your bones.
• Salt can make blood pressure medications less effective.

Two recent studies provide new incentives for people with high blood pressure to give the salt shaker fewer shakes.

In the first study, researchers at St. George’s, University of London, tested the effects of reducing salt by a third for six weeks in the diets of 169 white, black and Asian men and women ages 30 to 75, all with untreated mild hypertension. In all three ethnic groups, those who consumed less salt had a significant drop in blood pressure—meaning many with borderline high blood pressure should be able to lower their blood pressure to a normal level without medication. The researchers found the lower-salt diet also may have a beneficial effect on kidneys and bone.

“In other words, a lower salt intake over the long term may help prevent renal disease, cardiovascular disease and osteoporosis,” says the lead author of the study, Graham A. MacGregor, M.D., professor of cardiovascular medicine at St. George’s.

In the second study, researchers in Australia found that a high-salt diet may reduce the effectiveness of blood pressure medications in people whose blood pressure remains high despite taking several medications to lower it. The researchers recorded sharp declines in blood pressure when subjects reduced salt in their diet. They speculated that water retention caused by a high-salt diet might dampen the effect of the medications. Twenty to 30 percent of patients with high blood pressure may be resistant to multidrug therapies, say the authors. Both studies were published in the July 20 online edition of Hypertension.

“Most people don’t realize that sodium is added to almost all prepared foods today, even ice cream, and it is hard to avoid. Lowering the amount you add to your food yourself, however, is under your control, and it can make a huge impact on your health,” says Martha Daviglus, M.D., professor of preventive medicine at Northwestern University’s Feinberg School of Medicine.

Joan Rattner Heilman writes about health and consumer issues.