Using Diet to Lower Your Blood Pressure

Individuals with high blood pressure should not only put away the salt shaker, but eat more fruits, vegetables, and fat-free or low-fat dairy products, according to a statement from the American Heart Association (AHA) in today's Circulation: Journal of the American Heart Association.

One in four American adults has high blood pressure, which increases risk of stroke, heart attack and kidney failure.

For the first time, the American Heart Association's Nutrition Committee recommends adding fruits, vegetables and low-fat or fat-free dairy products to a reduced-salt diet to help prevent or lower high blood pressure.

In its statement, the Nutrition Committee recommended a diet rich in potassium, calcium and magnesium and low in total fat, saturated fat, cholesterol and sodium.

"First, this report reaffirms the importance of lowering and avoiding excess salt in the diet," says Theodore A. Kotchen, MD, author of the report and Professor of Medicine (Endocrinology) at the Medical College of Wisconsin. Dr. Kotchen, a member of the Medical College's Cardiovascular Research Center, is nationally known for his work on high blood pressure. "Secondly, it indicates that dietary components other than salt are also important in the control of high blood pressure," he says.

The committee's statement cites the Dietary Approaches to Stop Hypertension (DASH) trial, which found that a salt restricted diet rich in fruits, vegetables, and fat-free or low-fat dairy products produced the greatest reduction in systolic (top number) and diastolic (bottom number) blood pressures than the other two study diets.

The American Heart Association Nutrition Committee estimates that even a small reduction of just two points in diastolic blood pressure could lower a person's stroke risk by as much as 15% and lower heart disease risk by 6%.

Dr. Kotchen says that even though the DASH study relates a healthy diet to lower blood pressure, the specific nutrients in the DASH diet that lower blood pressure are only a guess.

Vegetables, fruits and dairy products are high in electrolytes, naturally occurring minerals such as potassium, magnesium and calcium. Dr. Kotchen says earlier studies have shown that individuals eating diets high in potassium that include foods such as bananas, dates, potatoes, and raisins tend to have lower blood pressure.

However, the Nutrition Committee is unable to say for sure whether the blood pressure lowering capacity of diets high in fruits, vegetables and low-fat dairy products is explained entirely by their electrolyte content.

For the general population, the AHA recommends that the average consumption of salt not exceed six grams daily. The committee says people with high blood pressure may need to limit their salt intake even more as recommended by their physician.

The AHA Nutrition Committee also recommends that individuals manage their weight and avoid having more than two alcoholic drinks per day.

Although the Nutrition Committee does not recommend high intake of calcium to prevent high blood pressure, calcium is still an important part of the diet for the prevention of other health problems such as osteoporosis.

"Nutritional strategies for the prevention and treatment of high blood pressure should address overall diet, rather than focusing exclusively on any single nutrient," Dr. Kotchen says. "Avoiding a high-salt diet, weight reduction in overweight individuals, and restricting alcohol intake are important."

Researchers on the DASH trial studied three diets in 459 adults with mild hypertension and high-normal blood pressure over an eight-week period. The first diet controlled potassium, magnesium and calcium levels and was used as a "control," or standard, for comparison with the two "study" diets. The study diets were either rich in fruits and vegetables or a combination of fruits, vegetables, and fat-free or low-fat dairy products. All three diets included 7.5 grains of salt daily.

The researchers found that participants on the "combination" diet lowered systolic blood pressure by an average of 5.5 mm/Hg, and diastolic by three mm/Hg. The fruit and vegetable diet lowered systolic by an average of 2.8 mm/Hg, and diastolic by 1.1 mm/Hg.

Coauthor of the statement is David A. McCarron, MD, of Oregon Health Science University, Portland.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.