Salt, DASH, and Blood Pressure
Medical Editor: Leslie J. Schoenfield, M.D., Ph.D.
Patients often ask what changes in life style can contribute to improving their blood pressure. In response, we doctors often recommend that reducing body weight, decreasing intake of dietary salt, and limiting consumption of alcohol can be beneficial. However, we need to now also consider the increasingly publicized DASH diet. This diet can bring about a reduction in blood pressure in people with normal blood pressure or high blood pressure (hypertension). Furthermore, when combined with a restricted dietary intake of salt, DASH actually has an additive effect in reducing the blood pressure.
DASH stands for "Dietary Approaches to Stop Hypertension." This diet is rich in fruits, vegetables, and grain (cereal) products. It also includes low-fat and fat-free dairy products, fish, legumes (e.g., peas and beans), nuts, poultry, and lean meats. The diet contains only small amounts of red meat, sweets, and sugar-containing beverages and is low in fat. The DASH diet is higher in potassium, calcium, magnesium, dietary fiber, and protein than the typical American diet.
The average intake of salt (sodium chloride) in the U.S. is approximately 9 grams per day, which contains 150 mmol, or 3.5 grams, of sodium per day. Reductions in the daily sodium intake to 100 mmol (2.3 grams), and then to 50 mmol (1.2 grams), lead to sequential reductions in blood pressure. When dietary salt restriction is combined with the DASH diet, an even greater reduction in blood pressure occurs at each level of sodium intake. The studies have indicated that the groups who have the best response to this combined approach are people older than 45 years, patients with hypertension, and African-Americans. Importantly, it is also thought that younger people with normal blood pressures who follow these combined dietary guidelines may develop less hypertension as they get older.
Studies combining the DASH diet with dietary sodium reduction have shown that some blood pressure reduction is possible in all population sub-groups. In fact, these sub-groups include those people who are known to be not very responsive to dietary sodium reduction alone, such as younger adults, persons without hypertension, and whites. Moreover, it is thought that following these combined dietary guidelines can have profound effects in reducing the heart (cardiovascular) disease (morbidity) and death (mortality) resulting from hypertension. Notably, this preventive effect on heart disease can occur even though the average reduction in systolic (top number) and diastolic (bottom) pressure is less than 10 mm Hg. What's more, the combined diet alone may be enough to control mild hypertension. However, patients with moderate to severe hypertension are likely to continue to additionally require some anti-hypertensive medications.
Studies have indicated that the overall dietary intake, rather than the intake of any single nutrient, is the key to reducing the risk of chronic diseases such as hypertension and heart disease. Accordingly, the current American Heart Association guidelines for all individuals recommends a diet similar to the DASH diet and an intake of less than 6 grams of salt per day, which is about 2.3 grams or 100 mmol of sodium. (Think, "Just a dash.") But, in addition, the guidelines recommend the maintenance of a healthy body weight by exercise and controlled caloric intake, no smoking, reduced intake of fat and cholesterol, and reduced alcohol intake. Note also that prepared foods tend to be high in salt and need to be restricted in the diet. It is important, therefore, to learn to read the nutrition labels on foods.
The beneficial effects of a low salt and DASH diet could be enormous when one considers that in the U.S., approximately 50% of the adult population and 80% of those over 50 years of age have a blood pressure of at least 120/80. (Remember that 120/80 is considered to be the upper limit of optimal blood pressure by national hypertension study groups.) Thus, attention to all of the life style and dietary issues mentioned above may lessen the increases in blood pressure that are so common in our society. Reducing the blood pressure, in turn, may limit the development of heart (cardiovascular) disease that can result from even mild hypertension. The bottom line is that we need to care for ourselves in the best possible way by following an optimal life style.
Last Editorial Review: 10/5/2002