A surprising new study by researchers at the University of Colorado at Boulder indicates that for postmenopausal women, reducing sodium may have a greater effect on lowering systolic blood pressure than regular exercise.
The study was carried out by researchers in the department of kinesiology and applied physiology under principal investigator and department Chair Douglas Seals. The results were published in a paper presented in the August Journal of the American College of Cardiology.
Systolic blood pressure is the first number given in a blood pressure reading. According to Seals, stiffness in the large elastic arteries -- primarily the aorta and carotid arteries -- tends to increase with age, and is often accompanied by a rise in systolic blood pressure.
This in turn is a major contributing factor to cardiovascular disease. The researchers speculate that restricting dietary sodium may play a much more active role than exercise in reducing the stiffness of the large elastic arteries.
The three-month study focused on 35 postmenopausal women with elevated systolic blood pressure. Half were asked to walk for 30 minutes per day, several days each week, while the other half were instructed to restrict their sodium intake to less than 2.4 grams per day, or less than 6 grams of salt.
The study found that both groups showed a decrease in systolic blood pressure, but for those who restricted their sodium intake the effects were "three-to four-fold greater," Seals said.
The study's results provide new insight for healthcare professionals, since there has been little research to date comparing the relative efficiency of various lifestyle changes as mechanisms for reducing blood pressure, he said.
"In treating patients with mild- to moderate- high blood pressure, physicians generally attempt to intervene with changes in lifestyle prior to placing them on a drug regimen," said Seals.
Primary care physicians generally have three options to choose from: regular exercise; reducing sodium intake in the diet; and weight loss. Physicians typically recommend that patients do all three, he said.
"Lifestyle interventions are merely tools to make the patient better," said Seals. "Of the two this study compared, dietary sodium restriction has the potential to produce the greatest reduction in blood pressure -- potentially normalizing systolic blood-pressure."
The subjects decreased their sodium intake by an average of 33 percent, which is considered a moderate reduction by experts in the field. The researchers believe that most older adults could undergo this level of change without imposing severe restrictions on their lifestyles.
Cardiovascular disease is the leading cause of death in the United States, according to the American Heart Association. Particularly at risk are older adults, whose percentage of the population will continue to rise as baby-boomers age.
After age 65, women have a greater prevalence of systolic hypertension than men, said Seals. "This was an important reason to focus on postmenopausal women in our study."
Approximately half of the subjects on each regimen also were on hormone replacement therapy. According to Seals, it was not obvious that hormone therapy had any effect on the relative effectiveness of the two lifestyle changes.
Other research groups participating in the study were the CU Health Sciences Center's department of medicine, The Colorado Prevention Center in Denver and the department of exercise and sport science at Colorado State University.