SCIENCE / MEDICINE : New Study Questions Benefits of Low-Salt Diets : Health: Limited research indicates that some people may actually need more salt to lower their blood pressure.

Trust no one until you have eaten much salt with him.--Cicero

In ancient times, salt was highly prized. Once it traded ounce for ounce with gold. Soldiers were paid in salt, giving rise to the modern term salary. It also served as an ancient preservative, a way of keeping food from decay.

Salt sharply flavors foods otherwise bland. Americans have developed an appetite for it, with adults consuming from seven to 10 grams of salt a day.

But in these modern times, salt has lost its savor. It has gone from something of value, and even necessary for life, to something that is considered harmful to health.

But a recent study has called the current scientific stance into question.

In the last 2 1/2 decades, studies of cardiovascular disease risk factors among large populations have associated high-salt diets with high blood pressure. High blood pressure raises the chances of dying from a stroke or heart attack. That led the U.S. Public Health Service to recommend that all of the nearly 60 million Americans with high blood pressure cut down on salt. And, tacitly, so should everyone else.

The fact is, not everyone is sensitive to salt, says Michael J. Horan, associate director for cardiology at the National Heart, Lung and Blood Institute. Only 30% of the American population has high blood pressure, and only half of these--or 15% of all Americans--are sensitive to salt. That means something like 85% of the population--including half of those with high blood pressure--can eat salt with impunity.

Because there is no easy way to tell whether a person is sensitive to salt, physicians reasoned it was better to recommend that all those at risk keep their hands off the shaker, since the avoidance of salt did not disclose any ill effects. That, however, may not be true. A recent study shows that lowering salt may be bad for some people, actually raising their blood pressure.

In an admittedly limited, but interesting, study of 27 white men in their mid-30s--some with mildly high blood pressure and the rest with normal pressure--Brent M. Egan, director of the hypertension program at the Medical College of Wisconsin in Milwaukee, found some surprises when he varied their salt intake.

The expected: “We found that . . . 10 of the individuals (37%), when they were on high-salt diets, had higher blood pressure, at least five millimeters of mercury (a measure of blood pressure) higher than on the low-salt diet,” Egan said. “There is no doubt that there are people who are sensitive to salt. Their blood pressure goes up when they eat salt.”

The unexpected: Thirteen men (48%) had higher blood pressure when they ate less salt. Lowering salt also raised the cholesterol levels in their blood, according to the study.

What is clear, Egan said, is that “people are not all the same, and that they respond differently to dietary salt manipulations.” This study, and a few similar ones, are small and do not show consistent outcomes, Horan said, so he is not ready to advise changing the recommendations made to people with high blood pressure.

Why the blood pressure of some men went up, however, is not clear. Egan believes it has to do with the hormone system in the body that regulates the amount of salt retained.

Variations in that hormone system probably are under genetic control. High blood pressure has a genetic component, because it runs in families. Obesity also raises the chances of developing the disorder, as does aging, with individuals possibly becoming more and more sensitive to salt with passing time.

These conflicting results are, of course, controversial.

Researchers such as Jeremiah Stamler, a cardiologist at Northwestern University Medical School in Evanston, Ill., believe strongly that if the population lowered its salt consumption, it would lower its blood pressure and risk of stroke and heart attacks.

Stamler bases his beliefs on Intersalt, a survey of 10,000 men and women in 32 countries that linked higher salt consumption to higher blood pressure. Stamler believes cutting salt consumption to three grams per day would lower blood pressure at least two millimeters of mercury, and that would reduce deaths from heart disease by 4% and strokes by 6%.

Other experts disagree with Stamler. Even Horan said the National Institutes of Health was careful not to recommend that the entire population cut its salt consumption because the data simply is not strong enough to justify it.

“We say you should find out which individuals benefit from salt restriction,” Egan said.

Worse still, Horan said, fewer Americans eat home-cooked food, relying more and more heavily on prepackaged products or eating out. Much of that prepared food already is heavily salted.

In the meantime, the debate goes on.