Lowering Blood Pressure: Diet or Exercise?

Both exercise and a low salt diet have been recommended for lowering blood pressure.   But results of a new study appearing in the Journal of the American College of Cardiology (Journal of the American College of Cardiology 2001;38:506-513) indicate that restricting dietary sodium may be the more important of the two. 

Blood pressure is recorded as two numbers — the systolic pressure, as the heart contracts, and the diastolic pressure, as the heart relaxes between beats. According to researchers, as the stiffness of the major arteries increases with age, so can systolic pressure — which is given as the first number in a blood pressure reading.

In the new study, investigators assigned 35 postmenopausal women with moderately high systolic blood pressure to take one of two measures: walk 3 to 4 days a week for 30 minutes a day or restrict their dietary sodium intake to less than 2.4 grams of sodium per day without changing their total calorie intake.  (NOTE: 1 tsp of salt has ~2200 mg of sodium chloride).

Dr. Douglas R. Seals from the University of Colorado Health Sciences Center in Denver and colleagues report that after three months women in both groups saw their blood pressure fall. But the reductions were three- to fourfold greater in women who restricted their salt in-take compared with those who walked.  For instance, the average drop in systolic pressure for women who cut their salt intake was about 16 mm Hg, compared with 5 mm Hg among those who exercised. Blood pressure that consistently stands at 140/90 mm Hg or above is considered high. Women in the study had systolic pressures ranging up to 159 mm Hg.

The results came as a surprise to Seals.  ”We expected regular aerobic exercise to produce similar or perhaps even greater reductions in blood pressure compared with moderate dietary sodium restriction. Instead, exercise did lower blood pressure, but the reductions with sodium restriction were much greater.”   But Seals also said that postmenopausal women will have the greatest impact on their blood pressure if they combine changes in diet with an exercise program and lose weight if they need to.

“It is important to emphasize the risk of disease associated with elevated systolic blood pressure for postmenopausal women, and actually middle-aged and older adults in general,” he noted.  “Only a few years ago it was believed that the diastolic blood pressure was the most important to control from the standpoint of predicting risk of future heart disease. We now know that in this population, elevated systolic blood pressure is the single most important risk factor for future development of heart disease.”

To lower dietary sodium, Seals advises people to refrain from adding salt to food and stay away from processed foods high in sodium.  “A lower-fat diet typically involves lots of fruits and vegetables and likely will achieve this goal, with the added benefit of reducing fat intake,” he said.

In Health Jeff