Blood pressure can be unhealthy even if it stays only slightly above the normal level of less than 120/80 mmHg. The more your blood pressure rises above normal, the greater the health risk.
Scientists supported by the National Heart, Lung, and Blood Institute (NHLBI) conducted two key studies. Their findings showed that blood pressures were reduced with an eating plan that is low in saturated fat, cholesterol, and total fat and that emphasizes fruits, vegetables, and fat-free or low-fat milk and milk products. This eating plan—known as the DASH eating plan—also includes whole grain products, fish, poultry, and nuts. It is reduced in lean red meat, sweets, added sugars, and sugar-containing beverages compared to the typical American diet. It is rich in potassium, magnesium, and calcium, as well as protein and fiber. (See box 2 for the DASH studies' daily nutrient goals.)
Box 2: Daily Nutrient Goals Used in the DASH Studies (for a 2,100 Calorie Eating Plan)
Total fat: 27% of calories
Saturated fat: 6% of calories
Protein: 18% of calories
Carbohydrate: 55% of calories
Cholesterol: 150 mg
Sodium: 2,300 mg*
Potassium: 4,700 mg
Calcium: 1,250 mg
Magnesium: 500 mg
Fiber: 30 g
* 1,500 mg sodium was a lower goal tested and found to be even better for lowering blood pressure. It was particularly effective for middle-aged and older individuals, African Americans, and those who already had high blood pressure. g = grams; mg = milligrams
The DASH eating plan follows heart healthy guidelines to limit saturated fat and cholesterol. It focuses on increasing intake of foods rich in nutrients that are expected to lower blood pressure, mainly minerals (like potassium, calcium, and magnesium), protein, and fiber. It includes nutrient-rich foods so that it meets other nutrient requirements as recommended by the Institute of Medicine.
The first DASH study involved 459 adults with systolic blood pressures of less than 160 mmHg and diastolic pressures of 80-95 mmHg. About 27 percent of the participants had high blood pressure. About 50 percent were women and 60 percent were African Americans. It compared three eating plans: a plan that includes foods similar to what many Americans regularly eat; a plan that includes foods similar to what many Americans regularly eat plus more fruits and vegetables; and the DASH eating plan. All three plans included about 3,000 milligrams of sodium daily. None of the plans was vegetarian or used specialty foods.
Results were dramatic. Participants who followed both the plan that included more fruits and vegetables and the DASH eating plan had reduced blood pressure. But the DASH eating plan had the greatest effect, especially for those with high blood pressure. Furthermore, the blood pressure reductions came fast—within 2 weeks of starting the plan.
The second DASH study looked at the effect on blood pressure of a reduced dietary sodium intake as participants followed either the DASH eating plan or an eating plan typical of what many Americans consume. This second study involved 412 participants. Participants were randomly assigned to one of the two eating plans and then followed for a month at each of the three sodium levels. The three sodium levels were a higher intake of about 3,300 milligrams per day (the level consumed by many Americans), an intermediate intake of about 2,300 milligrams per day, and a lower intake of about 1,500 milligrams per day.
Results showed that reducing dietary sodium lowered blood pressure for both eating plans. At each sodium level, blood pressure was lower on the DASH eating plan than on the other eating plan. The greatest blood pressure reductions were for the DASH eating plan at the sodium intake of 1,500 milligrams per day. Those with high blood pressure saw the greatest reductions, but those with prehypertension also had large decreases.
Together these studies show the importance of lowering sodium intake—whatever your eating plan. For a true winning combination, follow the DASH eating plan and lower your intake of salt and sodium.
Who Helped With DASH?
The DASH studies were sponsored by the NHLBI and conducted at four medical centers. There was also a central coordinating center at Kaiser Permanente Center for Health Research in Portland, OR. The four medical centers were: Brigham and Women's Hospital, Boston, MA; Duke Hypertension Center and the Sarah W. Stedman Nutrition and Metabolism Center, Durham, NC; Johns Hopkins Medical Institutions, Baltimore, MD; and Pennington Biomedical Research Center, Baton Rouge, LA.