Sodium (or salt) reduction – combined with either a typical U.S. diet or the DASH diet – substantially lowered blood pressure in people with high blood pressure and in those with slightly elevated blood pressure. That is according to a study by the National Heart, Lung, and Blood Institute of the National Institutes of Health. The DASH diet is one that is rich in vegetables and fruit, includes low-fat dairy products, and is low in total and saturated fat.
The DASH-Sodium study found that the lowest blood pressure levels were in those whose sodium intake levels were 1,500 milligrams a day or less and who also ate the DASH (Dietary Approaches to Stop Hypertension) diet. People who followed the DASH diet and kept their sodium level low, reduced their blood pressure more than those who only followed the DASH diet or only lowered their sodium intake.
"The DASH-Sodium study lays to rest the long-standing controversy over whether sodium reduction lowers blood pressure in people who do not have hypertension, more commonly called high blood pressure. The study also has important implications for the treatment of hypertension, which affects 50 million people in this country," says former NHLBI Director Dr. Claude Lenfant.
"These results challenge Americans to eat the DASH diet and to reduce sodium consumption, and challenges the food industry to reduce sodium levels in foods. Meeting these challenges, along with other lifestyle changes, could prevent the rise of blood pressure with age, and allow patients to control their hypertension with fewer or even no drugs," adds Dr. Lenfant.
Limit Salt to 1,500 mg Daily
"Following the DASH diet at the 1,500 mg of sodium level may prevent the development of high blood pressure and the increase in systolic blood pressure that typically occurs as people age," said Dr. Eva Obarzanek, the NHLBI Project Officer of the DASH-Sodium study. Other longer-term studies suggest that the benefit on blood pressure is likely to persist over the long term as long as people continue to follow the DASH diet and keep their sodium intake low, she adds.
How does one get to a daily level of 1500 mg of sodium (the equivalent of four grams or 2/3 teaspoon of table salt)? According to Dr. Obarzanek, the best way for people to lower sodium in their diets is to start by making a few simple changes:
- Buy unsalted or reduced-salt varieties of foods and condiments (crackers, soy sauce, pretzels)
- Take the salt shaker away from the table
- Don't use salt in food preparation
- Eat fewer processed foods – a major source of sodium. Or use lower-sodium versions, if available. This means cutting back on regular commercially prepared frozen dinners, packaged mixes, and canned soups or broths.
To gauge the sodium level of processed foods, read nutrition labels for sodium content and the percent daily value. Dr. Obarzanek suggests choosing foods that are less than five percent of the daily value for sodium. You can also select foods by milligrams of sodium per serving. For example, a food with 140 mg of sodium or less per serving is considered "low sodium," one with 35 mg sodium or less per serving is "very low sodium," and a food that has 0.5 mg sodium or less per serving is "sodium free." These are the definitions used to label food products.
Dining Out the Salt-Smart Way
Dr. Obarzanek has several suggestions for dining out. "Plan ahead and bank your sodium," she says. "If you know you're going to have a high sodium dinner at a restaurant, have a lower sodium breakfast and lunch." Other tips include "downsizing" – ordering the "kiddie" meal, which will have less sodium because it's a smaller portion; avoiding fried dishes since batter is salted; and ordering sandwiches with lettuce and tomato instead of mayonnaise, sauces, and condiments.
Healthy lower-sodium eating based on the DASH diet isn't just about restrictions, according to Dr. Obarzanek. To follow this plan, people should eat eight to 10 servings a day of fruits and vegetables (fresh, frozen, dried, or unsalted canned), seven to eight servings of grains and grain products, and two to three daily servings of low-fat or fat-free dairy foods. The DASH diet also calls for two or less daily servings of meat, poultry, and fish, and four to five servings a week of nuts, seeds, and dry beans.
Just as with sodium reduction, making small changes is the easiest way to begin following the DASH diet. Start out by trying to have two servings of fruits and/or vegetables at each meal and as snacks. Use fruit as dessert. To increase dairy foods, try to have one low-fat or fat-free dairy serving at each meal. Treat meat as part of the whole meal, not the focus, and emphasize vegetables, whole grains, and dry beans instead.
To add flavor to foods, use herbs, spices, lemon, lime, and vinegar rather than salt. Good snack options include unsalted pretzels or nuts mixed with raisins, graham crackers, low-fat and fat-free yogurt, plain popcorn, and raw vegetables.
Details of the Study
In the DASH-Sodium study, 412 people were randomly assigned to eat either a typical U.S. diet (the control diet) or the DASH diet, which is low in saturated fat, cholesterol, and total fat and emphasizes fruits, vegetables, and low-fat dairy foods. The DASH diet also reduces your intake of red meat, sweets, and sugar-containing drinks. It is rich in potassium, calcium, magnesium, fiber, and protein.
The DASH diet was initially used in the first DASH study, which examined the effect that whole dietary patterns had on blood pressure rather than looking at the effect of individual nutrients. The DASH diet was found to substantially reduce a person's blood pressure without necessitating a decrease in salt intake.
Participants in the DASH-Sodium study had all of their food provided. They ate their assigned diet for 30 days at each of three sodium levels: 3,300 milligrams per day (the average level consumed by Americans); an intermediate level of 2,400 milligrams per day; and a lower intake of 1,500 milligrams per day. At the start of the study, participants had systolic blood pressure (the top number in a blood pressure reading) between 120 and 159 mm Hg, and diastolic blood pressure of between 80 and 95 mm Hg. These ranges are similar to about 50 percent of the U.S. adult population. About 57 percent of the study participants were women and about 57 percent were African Americans. About 41 percent of study participants had high blood pressure (defined as total blood pressure over 140/90 mm Hg).
The DASH diet lowered blood pressure at each of the three levels of sodium intake. In addition, lower sodium intake resulted in lower blood pressure for those on both the typical and the DASH diets. This result applied to men, women, African Americans, Caucasians, and those with or without high blood pressure. Neither the DASH diet nor lower sodium intake caused undesirable effects.
"The combination of eating the DASH diet at a lower sodium level is a significant effect – equal to or greater than the result you would expect from treatment with a single hypertension medication," says Dr. Frank Sacks, chair of the DASH-Sodium Steering Committee and Associate Professor of Medicine at Brigham and Women's Hospital and Harvard Medical School. "However, the long-term health benefits of the low-sodium DASH diet will depend on whether the American public is willing to make long-lasting dietary changes, including choosing lower sodium foods, and whether the food industry makes available a greater number of lower-sodium food products," adds Dr. Sacks. |
