The DASH diet emphasizes whole grains, fruits, vegetables and low-fat dairy products. (iStock)
The question

Healthy eating has long been an important factor in lowering blood pressure. That usually means keeping salt intake low and eating foods high in such nutrients as potassium, calcium and magnesium. Do such dietary methods work for everyone, regardless of their blood pressure level?

This study

The researchers reanalyzed data from an earlier study that included 412 adults (average age, 48) whose systolic blood pressure (the first, or top, number) indicated pre-hypertension (for this study, considered to be 120 to 130) or Stage 1 or Stage 2 hypertension (130 to 160). No one was taking blood pressure medication. The participants had been randomly assigned to consume a normal American diet or the DASH diet, specifically developed to help lower blood pressure. In addition, in four-week intervals, the amount of sodium in the participants’ diets was adjusted to either a high level (reflecting Americans’ average daily intake), medium level (the recommended amount) or a low level (less than the recommended amount).

Among people in both groups, blood pressure dropped as the amount of sodium in the diet was reduced. However, the higher a person’s blood pressure was initially, the greater the rate of decline in blood pressure as sodium was reduced. Overall, people with higher blood pressure achieved the greatest reductions. For instance, a DASH diet/low-sodium combination, compared with a normal diet/high-sodium combination, lowered systolic blood pressure by about 10 points for those starting with a blood pressure of 140 to 149, but by 20 points for those with an initial blood pressure of 150 or higher. The researchers described the reduction among participants with the highest blood pressure as “striking.”

Who may be affected?

Adults who need to lower their blood pressure. The researchers noted that the effect of the dietary interventions was comparable to or better than the average achieved by such medications as angiotensin-converting enzyme inhibitors, calcium-channel blockers and beta blockers. The DASH diet emphasizes whole grains, fruits, vegetables and low-fat dairy products; it also includes some fish, poultry and legumes and a small amount of nuts and seeds. Red meat, sweets and fats can be eaten in small amounts, and saturated fat, cholesterol and total fat should be restricted. About a third of adults in the United States have high blood pressure, with only about half of them having it under control.

Caveats

The findings may not apply to people with extremely high blood pressure because the study excluded people with a systolic pressure of 160 or higher. The study was relatively short in duration.

Find this study

Online Nov. 12 in the Journal of the American College of Cardiology (onlinejacc.org; under “Issues,” click on “Articles in Press”).

Learn more

Information on high blood pressure can be found at nhlbi.­nih.gov/health (click on “Health Topics”). Learn more about the DASH diet at dashdiet.org.

The research described in Quick Study comes from credible, peer-reviewed journals.