Results from the Dietary Approaches to Stop Hypertension (DASH) trial show that dietary changes could affect blood pressure reductions on a par with drug therapy in persons with mild hypertension. The DASH diet emphasizes eating increased amounts of fruits and vegetables, and using low-fat dairy products. Sacks and colleagues report on a study that coupled the DASH diet with a reduction in sodium.
During the short-term (five-week) study, 412 adults were randomly assigned to either the DASH diet or a control diet designed to reflect typical consumption by many persons in the United States. Sodium intake for both groups varied from high (150 mmol) to intermediate (100 mmol) to low (50 mmol), in random order. The study group comprised approximately 55 percent blacks, 40 percent whites and 5 percent other ethnic groups. Mildly hypertensive and nonhypertensive persons were included. The average age of the patients was 48 years.
The biggest reductions in blood pressure were seen when the DASH diet was compared with the control diet, confirming the positive results of the previous DASH–diet study. In addition, a blood-pressure lowering effect was seen for each decrement in sodium intake in both groups. Not surprisingly, patients eating the less healthy control diet benefited more than those eating the DASH diet from sodium reduction. A combination of the DASH diet and low sodium intake reduced systolic pressure on average by 9 mm Hg, which favorably compares with reductions with usual drug monotherapy of mild hypertension. Diastolic blood-pressure lowering was more modest, with a maximum reduction of 4.5 mm Hg between the lowest and highest groups.
The study investigators conclude that a clinically significant additional blood-pressure lowering effect occurred as a result of reduced sodium intake in addition to that already seen with the healthful DASH diet. In an accompanying editorial, Greenland points out that the study was short (five weeks). He notes that while a 3-mm reduction in systolic blood pressure and a 1.6-mm decrease in diastolic blood pressure are clinically small effects, they are significant when viewed from a population-wide perspective. Observational studies suggest that even a 2-mm Hg reduction translates at a population level to a 17 percent decrease in the prevalence of hypertension and perhaps a 15 percent reduction in stroke and transient ischemic attack.