Americans who push their salt shakers away at home, only to be swamped by salt in take-out and restaurant fare, may get some help cutting back on the condiment. That's important, because we need salt to live - but in high doses, salt can worsen high blood pressure and increase the risk of heart disease and stroke.
The American Medical Association has adopted four recommendations seeking federal regulation of the salt in processed foods and restaurant meals. The doctors group is also calling for new public-education efforts and a new label - a red salt shaker - to warn consumers when food portions are high in salt.
The AMA wants the Food and Drug Administration to revoke salt's status as a food "generally recognized as safe," opening the door to regulation. It also hopes to work with the food industry to cut the salt in processed, take-out and restaurant food by at least 50 percent, but gradually, over 10 years.
The reason: An estimated 80 million Americans have high blood pressure, which can be triggered and worsened by high-salt diets, leading to increased risks for cardiovascular disease and death.
"That's almost half the population that (has) a condition that can be helped by industry doing things that are right, like letting consumers know how much of a potentially harmful substance is in the food they're buying and consuming in restaurants," said Dr. J. James Rohack, a Temple, Texas, cardiologist and immediate past chairman of the AMA's board of trustees.
Not everyone agrees. The Salt Institute, representing the nation's salt industry, says there is no scientific evidence that cutting everyone's salt intake will reduce overall mortality from cardiovascular disease - and the organization refers to some evidence that some people may be harmed.
"Following the AMA recommendation is scientifically unjustified and a waste of time and money," said Richard L. Hanneman, the institute's president. He called instead for carefully controlled studies of the health outcomes of dietary salt reductions.
Some salt is essential to human health. Chemically, table salt is sodium chloride (NaCl), composed of 40 percent sodium and 60 percent chlorine by weight. In nutritional discussions, however, salt and sodium are used almost interchangeably.
Mark Kurlansky, the author of "Salt: A World History," calls it "the only rock we eat." And we eat it because we have to.
Salt is vital to the body's regulation of water, acidity and the pressure within our cells. It is critical to nerve and muscle function, digestion and blood pressure.
Humans have long valued salt as a food preservative, flavoring and even as currency. It also tastes good, which helps ensure that we get enough.
The United States is the world's largest salt producer, according to the Salt Institute. The industry sold 32 million tons last year, worth a record $1.47 billion.
Most of that went to the chemical industry, or was used to de-ice highways. But nutritional salt production in 2005 totaled a record 1.6 million tons, worth $242.4 million.
Based on clinical studies, the federal government recommends that adults consume less than 2,300 milligrams of sodium per day. That's the sodium in just one-fifth of an ounce of salt.
The AMA report referred to studies suggesting a "substantial benefit" from reducing sodium intake to 1,500 milligrams per day. But more than 95 percent of American men ages 31 to 50 (and three quarters of the women) consume more than the recommended upper limit of 2,300 milligrams, the AMA said.
Seventy-five percent to 80 percent of our salt intake comes from the processed foods, take-out and restaurant food that Americans have turned to increasingly as the pace of our lives has picked up.
And we are paying dearly for it, Rohack said. He treats patients with hypertension and congestive heart failure every day, and nearly always starts by telling them to cut their sodium intake.
"Sodium is my life," he said.
Processors add salt to commercial foods to prevent spoiling and enhance flavor. As the salt enters the bloodstream, Rohack explained, the body retains water in order to maintain a proper salt/water balance.
"The simple way to know they got a lot of salt is when, a couple of hours after they eat the meal, they get thirsty," he said. That's your body saying it needs more water because "you've got too much salt on board."
Many of his patients will arrive home from a Texas barbecue and notice their feet and lower legs look puffy. That's salt-induced water retention.
For short periods, it's not an issue, Rohack said. The body will eventually rid itself of the extra salt and water. But a steady, high-salt diet "overloads the kidneys' ability to filter and get rid of the extra water," he said. The water increases blood volume, which increases blood pressure.
Hypertension is the most common cardiovascular ailment in the nation. In fact, after age 55, Americans have a 90 percent lifetime risk of developing high blood pressure.
High salt intake is especially troublesome in congestive heart failure, which is a weakening of the heart muscle and retention of fluids that can cause breathing difficulties. It's the No. 1 diagnosis among hospitalized Medicare patients.
Although there are many other risk factors to address - such as smoking, inactivity and obesity - Rohack says cutting salt intake gets results. "They wind up, many times, not requiring as many medications to control their condition. Especially for the heart failure patients, they don't have the 2 a.m. visits to the emergency room because they can't breathe."
It's not easy to avoid salt, he conceded. That's why the AMA wants to enlist government and the food industry to gradually reduce the salt all consumers encounter when they eat prepared foods.
But is it really a good idea?
Dr. Michael H. Alderman, a professor at Albert Einstein College of Medicine in New York and president of the International Society of Hypertension, doesn't think so.
There's no question, he said, that lowering blood pressure with medicine will "reduce the burden of strokes and heart attacks." It's equally clear that lowering salt intake will lower blood pressure.
But that, he argues, doesn't prove that cutting salt intake will, on the whole, save lives.
"The problem is that, when you change salt intake by that magnitude, other things change as well," he said. They include alterations in hormone systems that can increase risks of heart attack, stroke and diabetes.
"The health effects of any intervention, like salt, is the sum total of all its effects - good and bad effects," Alderman said. Individual salt requirements also vary widely according to occupation, climate and genetics.
"It's simplistic to say that all people, under all circumstances, all genes and behaviors should eat less salt. It sounds a bit dubious," he said.
In a review of 13 studies of the effect of salt reduction on patient mortality published in March by the American Journal of Medicine, Alderman and three colleagues found no clear consensus.
Unlike data on the health effects of cigarette smoking, which show overwhelmingly that smoking is "a killer," Alderman said, the epidemiological data on salt is "weak."
"That's why I think we need a clinical trial before we change the diets of 250 million Americans," he said. "I don't think we're facing a public health emergency."
The Salt Institute, which has engaged Alderman as an unpaid consultant and referred to his work in responding to the AMA, is likewise calling for more study of the issue.