February 1, 2010

The Health Benefits of Cutting Salt

Woman reading a nutritional label.

A computer model suggests that even a modest reduction in salt intake could significantly reduce the number of deaths nationwide from coronary heart disease.

High blood pressure, or hypertension, is a serious condition that can lead to coronary heart disease, heart failure, stroke, kidney failure and other health problems. About 1 in 3 adults in the United States has hypertension.

Blood pressure can be reduced by lowering dietary sodium. Experts recommend that people consume less than 2,400 milligrams of sodium a day—that's what's in about 6 grams of salt, or about a teaspoon. People with high blood pressure should shoot for 1,500 milligrams or less—about 3.7 grams of salt. However, the average man in the United States takes in over 10 grams of salt per day and the average woman over 7.

While some dietary sodium comes from people sprinkling salt on their food, about three-quarters comes from processed food, including breads and cereals, dairy products and processed meats. To limit dietary sodium, people need to read food labels carefully.

Some countries have reduced their populations' salt intake by using various strategies, such as regulating the salt content in processed foods, requiring labels on ready-to-eat foods and educating the public. Researchers led by Dr. Kirsten Bibbins-Domingo at the University of California, San Francisco, set out to explore the potential impact of a modest reduction in dietary salt on the health of the U.S. population.

The researchers built on the Coronary Heart Disease Policy Model, a computer simulation of heart disease in U.S. adults 35 to 84 years old. The data for the model came from several studies. These include the Centers for Disease Control and Prevention's National Health and Nutrition Examination Survey, the Framingham studies conducted and supported by NIH's National Heart, Lung and Blood Institute (NHLBI), and trials testing the effects of reduced salt on blood pressure and heart disease, such as NHLBI's Dietary Approaches to Stop Hypertension (DASH) trial. The new study was supported by NIH's National Center for Research Resources (NCRR) and the American Heart Association.

As reported in the January 20, 2010, online edition of the New England Journal of Medicine, the scientists found that reducing salt intake by 3 grams per day could cut the number of new cases of coronary heart disease each year by as many as 120,000, stroke by 66,000 and heart attack by nearly 100,000. It could also prevent up to 92,000 deaths each year. All segments of the population would benefit, with African-Americans having the greatest improvements overall. Women would particularly benefit from reductions in stroke, older adults from reductions in coronary heart disease and younger adults from lower mortality rates.

Reducing salt intake by 3 grams per day would save the country up to $24 billion in health care costs a year, the researchers estimated. Even a modest reduction of 1 gram per day between 2010 and 2019 would be more cost-effective than using medications to lower blood pressure in people with high blood pressure.

"Our study suggests that the food industry and those who regulate it could contribute substantially to the health of the nation by working toward reducing the amount of salt in the processed foods that all of us consume," Bibbins-Domingo says.

—by Harrison Wein, Ph.D.

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