A surprising new report questions public health efforts to get Americans to sharply cut back on salt, saying it’s not clear whether eating super-low levels is worth the struggle.

Most Americans eat way too much salt. It’s not just from salt shakers; sodium is hidden in processed foods and restaurant meals. Tuesday’s report stresses that, overall, the nation needs to ease back on the sodium for better heart health.

But there’s no good evidence that eating very low levels — below the 2,300 milligrams a day that the government recommends for most people — offers benefits even though national guidelines urge that certain high-risk patients do just that, the Institute of Medicine concluded.

Also, there are some hints, albeit from studies with serious flaws, that eating the lowest levels might harm some people — those who are being aggressively treated for serious heart failure, the report added.

The prestigious group, which advises the government about health, urged more and better research to settle the best target range.

“We’re not saying we shouldn’t be lowering excessive salt intake,” said Brian Strom of the University of Pennsylvania, who led the IOM committee. But below 2,300 milligrams a day, “there is simply a lack of data that shows it is beneficial.”

The average American consumes more than 3,400 milligrams of sodium a day, equivalent to 1 ½ teaspoons. U.S. dietary guidelines say most people should limit that to 2,300 milligrams a day, while some people — those older than 50, African Americans, and people with high blood pressure, diabetes or chronic kidney disease — should aim for 1,500 milligrams.

Tuesday’s report sparked an immediate outcry from health organizations that have long battled to lower the nation’s salt consumption.

The American Heart Association said it stood by its recommendations, stricter than the government’s, that everyone eat no more than 1,500 milligrams of sodium a day. Studies make clear that eating less sodium helps lower blood pressure and that lower blood pressure in turn leads to less heart disease, said heart association spokesman Elliott Antman, a cardiologist at Boston’s Brigham and Women’s Hospital.

“We’re sticking where we have the most solid evidence,” Antman said.

What to study is key to the debate: The IOM committee was asked to examine whether eating less salt directly affects longer-term outcomes such as heart attacks and death. That’s harder to prove, especially because the panel stressed that many of the studies it reviewed had quality problems.

Debating how little salt is too little is a moot point, said nutritionist Bonnie Liebman of the Center for Science in the Public Interest.

“The average American is still in the red zone, the danger zone,” she said.

The salt industry, in contrast, has long opposed the push for sharp sodium reductions and welcomed the report.

“There is no scientific justification for population-wide sodium reduction to such low levels, and the recognition by the IOM experts that such low levels may cause harm may help steer overzealous organizations away from reckless recommendations,” said Morton Satin of the Salt Institute.

Some salt is necessary for good health, although it’s not clear exactly how much.

But today, it’s very hard to cut back to 1,500 milligrams unless you always cook from scratch or eat too little food in general because of illness, Liebman added. Three-quarters of people’s daily sodium comes from processed or restaurant food. The average sandwich in a restaurant has 1,000 milligrams or more, and some restaurant meals can provide a full day’s supply of sodium in one entree, she said.

The Food and Drug Administration is working on a program to get food manufacturers to gradually lower sodium levels in their products, thus helping shoppers who don’t scrutinize food labels to get closer to dietary guidelines. The FDA said Tuesday that it was reviewing the IOM report, calling it consistent with its efforts “to work toward achievable and reasonable voluntary reductions in the sodium content of the U.S. food supply.”

Some restaurants already are taking steps. The Boston Market chain, for instance, has begun reducing sodium in its most-sold items by about 20 percent — and removed salt shakers from the restaurant tables. “Where’s the salt shaker?” read signs sitting next to the pepper that explain the chain’s move to reduce sodium and advise that customers who really want an extra pinch will have to get up to find some at the counter.

— Associated Press