New study: reducing salt & following the DASH diet adds up to lower BP

stethoscope and blood pressure cuffGreat news for patients with hypertension: A new study from Beth Israel Deaconess Medical Center has found that the combination of cutting back on salt and eating the nutritionally-rich DASH (Dietary Approaches to Stop Hypertension) diet can significantly lower systolic blood pressure after just one month — with results equal to or better than some blood pressure medications, in some cases.

Recently published in the Journal of the American College of Cardiology, the results also found that individuals with the highest systolic blood pressure readings — at or above 150 mm/Hg — had the greatest improvements when they followed the two dietary recommendations, with systolic blood pressure dropping as much as 21 points.

(Blood pressure is measured in units known as millimeters of mercury, abbreviated as mm Hg.)

“Lifestyle measures such as restricting sodium intake, losing weight, and regular exercise are the first steps in reducing blood pressure,” says Joseph Kannam, MD (right), Chief of Cardiology at Beth Israel Deaconess Hospital-Needham. “This study illustrates the significant effect that diet and sodium restriction can have on blood pressure.”

“Eating too much salt and too many high-sodium processed foods are well-known risk factors for high blood pressure,” says study author Stephen Juraschek, MD, PhD, an internal medicine physician at BIDMC and Instructor in Medicine at Harvard Medical School.

The U.S. Food and Drug Administration (FDA) recommends a daily limit of one teaspoon of salt per day, approximately 2,300 milligrams of sodium.

Systolic blood pressure is the top number in the blood pressure reading and indicates how much pressure is being exerted by the blood against the artery walls every time the heart beats.

“Regardless of their starting blood pressure, participants in our study — a total of 412 people with pre-hypertension and stage 1 hypertension — on average saw their systolic blood pressure lowered when they either reduced salt or switched to the DASH diet,” says Juraschek. “But the patients with the least controlled blood pressure, who did both interventions, showed the greatest improvements.”

The DASH diet was developed by the National Heart, Lung and Blood Institute as part of a program to lower blood pressure.

Diet Changes Led to Significant Blood Pressure Drops

salt shakerThe participants in the study averaged 48 years of age. They were randomly assigned to eat the equivalent of either one-half teaspoon of salt, one teaspoon of salt or 1.5 teaspoons of salt per day over a four-week period.

Participants were also randomly assigned to either a diet typical of the American diet or to switch to the DASH diet, which emphasizes consumption of fruits, vegetables, whole grains, low-fat or fat-free dairy products, fish, poultry, beans, and nuts. 

The study findings showed that:

  • Eating the DASH diet, but continuing to eat higher amounts of salt, led to a drop in systolic blood pressure between 4.5 points and nearly 11 points for individuals whose initial systolic blood pressure averaged 135 mm/Hg.
  • For these same individuals, cutting back on salt, but maintaining a regular diet, led to a drop in blood pressure of between seven and 10 points.
  • Combining the two changes resulted in dramatic improvements, says Juraschek, particularly among the individuals who started with the highest blood pressure readings: “We found that these two changes combined could lower systolic blood pressure more than 20 mm Hg.”

“To place this in context, in order to approve a new anti-hypertensive drug, the FDA has said the drug should lower systolic blood pressure at least 3 to 4 mm Hg,” Juraschek adds.“Similarly, if you look at common classes of blood pressure medications like ACE inhibitors, beta blockers, or calcium channel blockers, they lower blood pressure, on average, by 10 to 16 mm Hg. The effects we observed from diet are of a similar magnitude — and in some cases are greater than blood pressure drugs.”

Above content provided by the CardioVascular Institute at Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.

Winter 2018