New York City's health tsar, who has already waged war against tobacco, trans fats, and calories, appears to have chosen his next public enemy: salt.

Voicing cautionary tales about high blood pressure that can be caused by eating too much salt, officials from the city's Department of Health and Mental Hygiene in recent months have used editorials, public testimony, and educational campaigns to mount a push for regulation of sodium levels in food.

"In many ways, high blood pressure is a forgotten killer. It's the leading cause of early death in New York City and nationally," the city's health commissioner, Dr. Thomas Frieden, told The New York Sun. He cited a study by the health department, published last week in the journal Circulation: Cardiovascular Quality and Outcomes, which found that one in four New Yorkers, or 26% of adults, has high blood pressure, compared to 30% nationally. The rate among New Yorkers older than 65 is 71%.

"We've done some health education on salt, but the fact is that it's in food and it's almost impossible for someone to get it out," Dr. Frieden said. "Really, this is something that requires an industry-wide response and preferably a national response."

As health commissioner, Dr. Frieden has made a name for himself by enacting measures such as a ban on smoking in restaurants and bars, and for passing laws targeting unhealthy foods and eating habits. Since May, fast-food and chain restaurants in New York City have been required to post calorie information on their menus. In July, health officials began enforcing a ban on artificial trans fats, a type of fat derived from partially hydrogenated vegetable oil. Restaurants that violate either law can be fined $2,000.

In an editorial published in the August 27 issue of the Journal of the American Medical Association, city health officials promoted New York City's efforts so far regarding trans fats and calories, and they set their sights on new areas of health policy.

"It is more challenging  but even more important  to reduce consumption of sodium and sugar," the authors, the assistant commissioner for chronic disease prevention at the health department, Dr. Lynn Silver, and the department's deputy commissioner for health promotion and disease prevention, Dr. Mary Bassett, wrote.

Citing data showing that Americans consume nearly twice the recommended daily allotment of sodium of 2,400 milligrams, according to the Food and Drug Administration, Drs. Bassett and Silver argued that reducing the sodium content of food would save more lives than treating all hypertensive individuals with blood pressure medication.

"Processed and restaurant foods account for 77% of salt consumption, so it is nearly impossible for consumers to greatly reduce their own salt intake," they wrote. Similarly, regarding sugar, they wrote: "Reversing the increasing intake of sugar is central to limiting calories, but governments have not done enough to address this threat."

For their part, health officials last year launched a "Cut the Salt!" campaign to educate Brooklyn residents about the harmful effects of consuming too much salt.

However, their efforts are largely focused on a national solution. Last November, city health officials testified at an FDA hearing, urging the federal government to lower the sodium content of restaurant and processed foods. They also recommended a national labeling system to warn consumers about high sodium in certain food products.

Such comments prompted some critics to speculate that the health department will move forward with local regulation.

"Yes, I do believe this is the first foray in the department of health's camp to turn sodium into the next trans fats," the medical director of the American Council on Science and Health, Dr. Gilbert Ross, said.

Dr. Ross questioned whether city health officials would be satisfied with petitioning the food industry to offer lower sodium choices, because in the past their efforts to persuade restaurants to voluntarily adopt a certain health measure resulted in new laws. "The New York City department of health is looking for food hobgoblins everywhere," Dr. Ross said.

Critics said the city seems to be taking cues from an advocacy group, the Center for Science in the Public Interest, which advised the Department of Health and Mental Hygiene on its calorie labeling law. The group has petitioned the FDA to characterize salt as an "additive" that is subject to limits, instead of something that is "generally recognized as safe," and is not subject to limitations.

"If the government were serious about this, it could force industry to cut the salt," the center's executive director, Michael Jacobson, said. He pointed to a public education campaign in Britain that was designed to pressure the salt industry to lower sodium content in food, and called on the FDA to mount a similar campaign.

Absent federal action, Mr. Jacobson said local governments could find powerful roles. "Cities and states could certainly threaten warnings on the labels or on supermarket walls," he said. "Even New York City on its own is a little scary because they've seen menu labeling and trans fat," he said.

To be sure, medical doctors said salt is associated with increased blood pressure in many patients. The American Heart Association recommends that adults consume less than 1 teaspoon of salt daily, or about 2,300 milligrams. Doctors said most Americans consume far more sodium than the recommended allotment, and that foods high in salt also tend to have high calorie counts.

"The end result is whatever reason you have high blood pressure, and it's untreated, you're at a higher risk for heart attack and stroke. You're also at risk for kidney disease and eye problems," a New York City cardiologist who is the author of "The Women's Healthy Heart Program," Dr. Nieca Goldberg, said.

In 2006, the American Medical Association called for a 50% decrease over the next decade in the amount of sodium in processed foods and meals served in restaurants. The group also encouraged the FDA to develop warning labels for foods that are high in sodium.

Dr. Frieden said the AMA and others with similar stances "have it right."

"We should look for a steady, gradual salt reduction," he said.

He also hinted that regulating salt consumption would be trickier than passing laws banning trans fats or requiring restaurants to post calorie information. Sodium is considered to be an essential mineral, necessary for helping the body absorb major nutrients. "The problem is not putting salt on at the table," Dr. Frieden said. "The problem is salt that's mixed in."

Indeed, some doctors said putting the entire population on a low-salt diet could be harmful.

"Of the environmental factors, salt is one of the factors that clearly and significantly affects blood pressure in many," a professor of clinical medicine at NewYork-Presbyterian Hospital/Weill Cornell Medical Center, Dr. Samuel Mann, said.

He urged restraint. "The other question is, 'Can you do harm by salt-restricting everyone?' and the answer is, 'Yes.' Most people need little salt, but some need more, particularly those who tend to run a relatively low blood pressure, and as a result tend to crave salt," he said. He recommended moderate, rather than severe, reduction in the salt content of foods.

Critics of efforts to regulate salt voiced opposition to restrictions of any kind.

"We don't want to be blamed for a problem that we don't feel we're causing," the president of the Salt Institute, Richard Hanneman, said. The group represents major salt corporations, and on its Web site it said the industry produces 1.5 million tons of food-grade salt each year, with annual sales topping $286 million.

According to Mr. Hanneman, science has not shown there is a health benefit to widespread salt reduction, a view held by a minority of doctors. He further called for a federally funded study of the impact of salt reduction. "We're not saying if your doctor says to go on a low-salt diet that you shouldn't do it," he said. "We're saying for a healthy population, it's a mistake to ask everyone to reduce their salt."

In New York, the executive vice president of the New York State Restaurant Association, Charles Hunt, said his group has known for some time that the city's health department was eyeing salt as a possible target. He said any efforts to limit salt consumption should take place at home, as only about 25% of meals are consumed outside the home.

"I'm concerned in that they have a tendency to try to blame all these health problems on restaurants," he said, stressing that his members are concerned about the health of their customers.

"This nanny state that has been hinted about, or even partially created, where the government agencies start telling people what they should and shouldn't eat, when they start telling restaurants they need to take on that role, we think its beyond the purview of government," Mr. Hunt said.