DASH DIETS for BP

By P.L. Jennings
5/19/00 HeartInfo
A low-sodium diet can decrease systolic blood pressure by as much as 11.5 mm Hg, according to findings from a new study presented on Wednesday at the American Society of Hypertension (ASH) annual meeting in New York City.

The findings, which will be published later this year, are from the DASH-Sodium trial, a study supported by the National Heart, Lung, and Blood Institute (NHLBI), a division of the National Institutes of Health (NIH). "Earlier studies had differed in their designs, leading to uncertainty over how worthwhile it is to reduce dietary sodium for those who have not yet developed high blood pressure," said NHLBI director Dr. Claude Lenfant. "This well-controlled study had a diverse group of participants and its findings show that the benefit is substantial."

DASH is short for "Dietary Approaches to Stop Hypertension". The DASH-Sodium trial is a follow-up to an earlier study involving the effects of dietary patterns on blood pressure. Results of the original DASH study, published three years ago in The New England Journal of Medicine, indicated that a diet low in fat and cholesterol, which emphasizes fruits, vegetables, and low-fat dairy products can significantly reduce blood pressure. DASH-Sodium examined the relationship between blood pressure and sodium intake, both among those following the DASH diet and those adhering to a more typical American diet.

Dr. Frank Sacks, chair of the DASH-Sodium Steering Committee and Associate Professor of Medicine at Brigham and Women's Hospital and the Harvard Medical School, led the presentation of his team's findings.

According to Dr. Sacks, the study involved 412 adults over the age of 21. Participants had systolic blood pressures of 120-159 mm Hg and diastolic blood pressures of 80-95 mm Hg. Approximately 41 percent had hypertension. Participants were randomly assigned to one of two dietary plans, each of which included three sodium levels. The dietary plans included what was considered to be a typical American diet, and the DASH diet. Sodium levels included a high range of 3,300 milligrams per day, an intermediate range of 2,400 milligrams per day (the currently recommended level), and a low range of 1,500 milligrams per day. All food was provided to participants over the course of the 14-week study.

Dr. Sacks reported that the greatest reductions in blood pressure were found among those who followed the DASH diet at the low sodium level (1,500 milligrams per day). This was true of both those with and without hypertension. However, results showed that reducing dietary sodium lowered blood pressure for those receiving the typical American diet as well.

Overall, the DASH diet combined with low sodium intake reduced systolic blood pressure by an average of 8.9 mm Hg and diastolic blood pressure by an average of 4.5 mm Hg. In those with hypertension, the combination reduced systolic blood pressure by an average of 11.5 mm Hg; in those without hypertension, the combination reduced systolic blood pressure by an average of 7.1 mm Hg.

Asked if they would be making any official recommendations to the government based on their results, Dr. Eva Obarazanek, an NHLBI nutritionist and Project Officer for DASH-sodium, stated:

"The findings suggest that the current recommendation of how much dietary sodium Americans should consume may need to be lowered. By reducing their dietary sodium to 1,500 mg a day, all Americans, and especially those at a high risk for hypertension, can decrease their chance of developing high blood pressure as they age."