A diet rich in fruits, vegetables and low-fat dairy products can reduce blood pressure as much as the most commonly used hypertension drugs, eliminating the need for the expensive drugs in many patients with mild hypertension, according to a major multicenter study published today.
Previous studies had shown that reducing weight, lowering salt consumption and minimizing alcohol use also could reduce blood pressure. But the new study, published in the New England Journal of Medicine, is the first to show that changing the overall diet will reduce blood pressure independently of those other factors.
Widespread adoption of the combination diet, the team said, could potentially reduce the risk of heart disease by 15 percent and the likelihood of stroke by 27 percent.
"With nearly 50 million Americans having hypertension, and considering the billions of dollars spent each year on blood pressure medications, these findings have important public health considerations," said Dr. George Blackburn, president of the American Society for Clinical Nutrition.
"This is one of the best pieces of news for people in this country in a longtime," said Dr. David McCarron of the Oregon Health Sciences University. "We've never had a dietary intervention that gives this kind of effect in terms of improving life expectancy."
The study was not designed to identify which components of the diet were responsible for its beneficial effects, but McCarron and others speculate that the calcium in milk may confer the greatest blood pressure-lowering benefits. Many blood-pressure drugs, such as diuretics and calcium-channel blockers, work by increasing calcium retention.
"It's reasonable to assume that the dairy products in the diet are doing the same thing," McCarron said.
"This has important implications for the African American community," he said. Blacks have two to three times the normal level of hypertension and consume fewer dairy products than caucasians.
"This is also important for men, who have more hypertension than women," he added. "Most men are not getting enough calcium, and they need to get serious about it. Even if they don't worry about their bones, they should start worrying about their hearts."
High blood pressure is one of the primary risk factors for heart attacks and stroke.
According to the American Heart Association, at least 24 percent of Americans have blood pressure greater than the ideal level of 120/80. Four out of every five of those have moderate hypertension, meaning their blood pressure is between 160/95 and 120/80.
The trial, called Dietary Approaches to Stop Hypertension, or DASH, was sponsored by the National Institutes of Health. The team enrolled 459 people with blood pressures below 160/95 - about two-thirds with moderate hypertension and one-third with borderline normal blood pressure - in centers in Baltimore, Boston, Durham, N.C. and Baton Rouge, La. Almost half were women and 59 percent were black. None were taking medications to control their blood pressure.
Participants received all their food from the study for 11 weeks, and on weekdays they ate their main meal at the clinics to ensure compliance. For the first three weeks of the study, each participant received a "typical American" control diet, then was randomly assigned to one of three groups.
One group continued to receive the control diet; one received a diet rich in fruits and vegetables; and one received the combination diet, rich in fruits, vegetables and low-fat dairy products and reduced in saturated fat. All diets contained the same amount of salt.
The effects of the diet were obvious within one week and reached their maximum value within two weeks. Blood pressures then remained stable for the final six weeks.