A national program to reduce dietary salt could prevent tens of thousands of heart attacks, strokes and deaths and trim as much as $24 billion from the U.S. health-care tab, according to a study published Wednesday in the New England Journal of Medicine.

The study, a computer simulation, suggests the impact would be similar to prevention strategies such as quitting smoking, lowering cholesterol or modest weight-loss.

But significant cuts in salt from the diet could be challenging for individuals without action from food manufacturers. Some 75% of dietary salt intake comes from processed foods, according to the researchers.

A salt-reduction program in the U.S. could save an estimated $10 billion to $24 billion in annual health costs.

Their findings add to a growing body of research suggesting that lowering dietary salt could be an effective weapon against high blood pressure and cardiovascular disease. “The time is right now to consider efforts to…achieve population wide reduction in salt” intake, says Kirsten Bibbins-Domingo, first author of the study and an associate professor of medicine and epidemiology at the University of California, San Francisco.

Last week, the New York City Health Department said it would encourage packaged food makers and restaurants to cut salt by 25% over five years. Many food manufacturers have long sold “low sodium” versions of products, but generally they haven’t been popular with consumers. Some companies have recently begun cutting sodium content without highlighting it on product labels.

Morton Satin, technical director of the Salt Institute, a nonprofit group of salt producers, says few data exist linking salt intake and disease. He is skeptical that reducing salt will yield important health benefits.

Americans consume far more than the recommended daily salt intake. The average adult male consumes more than 10 grams of salt a day, according to the U.S. National Health and Nutrition Examination Survey. On Wednesday, the American Heart Association published new guidelines calling for all Americans to reduce their daily intake of sodium—a key component of salt—to 1,500 milligrams, equivalent to 3.8 grams of salt. Previously, that was the recommended limit for higher risk individuals; the regular limit had been 2,300 milligrams of sodium, or 5.8 grams of salt.

A typical sandwich, with two slices of bread and meat or peanut butter, has about half the daily recommended amount of salt, Dr. Bibbins-Domingo says.

In the computer simulation, which included data from the U.S. Census, the Centers for Disease Control and Prevention and other national studies, Dr. Bibbins-Domingo and her colleagues estimated the effect of lowering salt in the daily American diet by a small amount—up to three grams a day—in adults age 35 and older.

Based on other research, they assumed a three-gram reduction in salt would lower systolic blood pressure by 3.6 to 5.6 millimeters of mercury; a one-gram reduction would reduce the level by 1.2 to 1.9 millimeters. (Systolic is the higher number in a blood-pressure reading. People whose level is 140/90 or more are considered to have high blood pressure.) Such modest blood-pressure reductions are associated, in other studies, with significant lowering of risk of death, heart attack and stroke.

In the current study, researchers found that lowering salt intake by three grams a day would cut new cases of heart disease annually by a third—an estimated 60,000 to 120,000 cases per year—heart attacks by 54,000 to 99,000 cases and strokes by 32,000 to 66,000 cases. It would reduce about 100,000 deaths a year in the U.S.

Based on a cost of $1 a person for salt-reduction strategies projected by the World Health Organization, researchers estimated a U.S. program could save from $10 billion to $24 billion in annual health costs. Such projections can be imprecise because they are based on assumptions that may differ from disease that would develop in real life.

But even if these numbers are off, the results still indicate that sodium reduction is important, said Clyde Yancy, president of the American Heart Association and medical director of the Baylor Heart and Vascular Institute in Dallas. “We can go beyond saying that too much salt is a bad thing,” said Dr. Yancy. “We can say, yes, too much sodium is related to disease. By reducing sodium we can reduce disease.” By Shirley S. Wang, The Wall Street Journal