By Steven Reinberg
NEW YORK (Reuters Health) – Individuals who follow the Dietary Approaches to Stop Hypertension (DASH) diet and also reduce their salt intake have significantly greater reductions in blood pressure (BP) compared with those who only follow the diet or reduce salt intake, researchers report in the Annals of Internal Medicine for December 18.
"The combination of the DASH diet and low sodium lowered BP in all the subgroups we studied including young and old, men and women, African-Americans, non-African-Americans, and those with and without hypertension," Dr. William M. Vollmer from the Center for Health Research, Portland, Oregon, told Reuters Health.
Dr. Vollmer and colleagues randomly assigned 412 men and women to the DASH diet, a low-fat diet with high levels of fruits and vegetables, or to typical US diet, for three consecutive 30-day periods. For each 30-period, sodium intake was 50 mmol/day, 100 mmol/day or 150 mmol/day.
The trial participants had untreated systolic BP of 120 mm Hg to 159 mmHg and diastolic BP of 80 mmHg to 95 mmHg, the researchers note.
An analysis of the subgroups showed that all patients on the DASH diet, as well as all of those who reduced their sodium intake, had significant drops in BP. For example, nonhypertensive subjects older than 45 years of age who were on the control diet reduced mean BP by 7.0/3.8 mm Hg, while those 45 years of age or younger reduced their mean BP by 3.7/1.5 mm Hg (p < 0.05).
"Following the DASH diet and reducing salt intake was better than doing either one alone," Dr. Vollmer added. Overall, systolic BP reductions ranged from 7 to 12 mmHg, with the greatest reduction seen among patients older than 45 years of age and in women.
"Vollmer and colleagues' trial advances knowledge concerning the magnitude and certainty of short-term effects of low-salt and very-low-salt diets on blood pressure," Dr. Cynthia Mulrow from the University of Texas Health Science Center, San Antonio comments in a journal editorial.
"But given the difficulty of achieving and maintaining very-low-salt diets, the uncertain clinical benefits of either low-salt or very-low-salt diets, and the fact that other therapies have clearer proven clinical benefits, these findings do not give clinicians reason to move salt restriction to the top of the list of items to be discussed with hypertensive adults," Dr. Mulrow writes.
However, Dr. Mulrow adds that identification of patients on high-salt diets is easy, and these individuals may benefit and are unlikely to be harmed by eating fruits and vegetables and reducing dietary salt.