NEJM Study Shows Diet, Low Sodium Intake Lowers Blood Pressure

BOSTON--It's a fact--an overload of salt may be bad for you. The New England Journal of Medicine (NEJM) (344 (1):3-10, 2001) published a study Jan. 4 stating the positive effects of reducing sodium uptake in conjunction with the Dietary Approaches to Stop Hypertension (DASH) diet. The DASH program, supported by the American Heart Association, is rich in vegetables, fruits, grains, low-fat and fat-free dairy products, fish, legumes, poultry and other lean meats.

In the NEJM study, 412 participants--with and without hypertension--were randomly assigned either a control diet mirroring the "typical," high-fat American diet or the DASH diet. Within each diet, participants consumed foods containing high (3,300 mg/d), intermediate (2,400 mg/d) and low levels (1,500 mg/day) of sodium for 30 consecutive days.

The researchers, led by Frank M. Sacks from the department of medicine at Harvard Medical School, noted that subjects with higher sodium levels at the start of the study experienced greater reductions in blood pressure levels. In the control group, researchers reduced sodium intake from a high to intermediate level, thereby reducing systolic blood pressure by 2.1 mm Hg (millimeters of mercury); in the DASH group, systolic blood pressure reduced by 1.3 mm Hg. By reducing sodium from an intermediate to low level, there was an additional reduction of 4.6 mm Hg in the control group and 1.7 mm Hg in the DASH group. The National Institutes of Health's (NIH) National Heart, Lung and Blood Institute sponsored the study and NIH noted that having blood pressure with even slight elevations above the recommended level of 120/80 mm Hg is unhealthy.

Compared to the control diet with a high sodium level, the DASH diet led to a mean systolic blood pressure that was 7.1 mm Hg lower in participants without hypertension and 11.5 mm Hg lower in participants with hypertension.

The researchers concluded that participants who reduced sodium to 1,500 mg per day (equivalent to 4 g or two-thirds of a teaspoon of table salt) and followed the DASH diet experienced the best results for lowering blood pressure levels. "Long-term health benefits will depend on the ability of people to make long-lasting dietary changes and the increased availability of lower-sodium foods," noted the researchers.

In an editorial in the same issue of NEJM, Philip Greenland, M.D. from Northwestern University Medical School, wrote that the researchers "address previously unanswered questions about the separate and interactive effects of a reduction in dietary sodium and the DASH diet on blood pressure." In addition, this was the first trial where sodium intake levels were varied.

Greenland also wrote that the people most affected by consuming a DASH diet along with reducing sodium intake included blacks, women, older people and people with hypertension. "The main message of this new trial, stated forcefully by the authors, is that the results appear to be applicable to most people in the United States," Greenland said, adding that observational studies indicate that an overall dietary pattern--as opposed to a single nutrient or food--is most effective in reducing the risk of chronic disease.

Media outlets widely reported the study results, while mainstream food organizations responded as well. The Grocery Manufacturers Association (GMA) noted that it "applauded" the study, adding that the key is "moderation, not martyrdom." The National Food Processors Association (NFPA), meanwhile, encouraged consumers to follow dietary guidance and use labels wisely. "It is important to know that the amount of sodium in foods is clearly labeled on food packaging," said Rhona Applebaum, executive vice president of scientific and regulatory affairs. "The wide variety of food products on the market--coupled with the information contained on nutrition label--are critical components that enable consumers to choose food products appropriate for their dietary needs."

For an abstract of the study, visit www.nejm.org.