But Bonnie Liebman, director of nutrition at the Center for Science in the Public Interest, an advocacy group that has taken a strong position against excessive salt consumption, worried that the public would get the wrong message.

“It would be a shame if this report convinced people that salt doesn’t matter,” Ms. Liebman said.

The American Heart Association agrees with her. Dr. Elliott Antman, a spokesman for the association and a professor of medicine at Brigham and Women’s Hospital in Boston, said the association remained concerned about the large amount of sodium in processed foods, which makes it almost impossible for most Americans to cut back. People should aim for 1,500 milligrams of sodium a day, he said.

“The American Heart Association is not changing its position,” Dr. Antman said. The association rejects the Institute of Medicine’s conclusions because the studies on which they were based had methodological flaws, he said. The heart association’s advice to consume 1,500 milligrams of sodium a day, he added, is based on epidemiological data and studies that assessed the effects of sodium consumption on blood pressure.

The Institute of Medicine committee said it was well aware of flaws in many of the studies of sodium, especially ones that the previous Institute of Medicine committee relied on for its 2005 recommendations. Much of that earlier research, committee members said, looked for correlations between what people ate and their health. But people with different diets can differ in many ways that are hard to account for — for example, the amount of exercise they get. And relying on people’s recall of how much salt they consumed can be unreliable.

Even the ways previous studies defined high and low sodium consumption varied widely.

“In one study, it was high if it hit 2,700 milligrams a day. In another study, it was high if it hit 10,000 milligrams a day,” said Cheryl A. M. Anderson, a committee member who is an associate professor of family and preventive medicine at the University of California, San Diego.

The committee said it found more recent studies, published since 2005, that were more careful and rigorous. Much of the new research found adverse effects on the lower end of the sodium scale and none showed a benefit from consuming very little salt.

Although the advice to restrict sodium to 1,500 milligrams a day has been enshrined in dietary guidelines, it never came from research on health outcomes, Dr. Strom said. Instead, it is the lowest sodium consumption can go if a person eats enough food to get sufficient calories and nutrients to live on. As for the 2,300-milligram level, that was the highest sodium levels could go before blood pressure began inching up.