Instructions: Two studies with new twists are shaking up the old salt debate.

The first study, called DASH, showed that eating a healthful diet lowers blood pressure signficantly and quickly. The second, called DASH-Sodium, has reignited controversy over whether eating less salt can reduce your chances of getting heart disease.

So far, the results seem to say the less salt the better - even if you dont have high blood pressure.

One in four adult Americans has high blood pressure, as do half of all Americans over age 60. Nearly 50 million Americans have "high normal"

blood pressure (130/85 and above).

High blood pressure raises your chances of having a stroke or heart attack.

But there are no symptoms, so high blood pressure, also called hypertension, is called the "silent killer."

At Portlands Kaiser Permanente Center for Health Research, the first DASH

(Dietary Approaches to Stop Hypertension) study found that people were able to lower their high blood pressure considerably by eating four to five servings each of fruits and vegetables every day.

The readings dropped even more when they also cut back on fat, saturated fat and cholesterol and ate more low-fat and nonfat dairy foods. Participants all got the same amount of sodium, about 3,000 milligrams - close to what Americans usually get each day.

Other studies nationwide have examined whether specific nutrients, such as magnesium and calcium, could lower or even possibly raise blood pressure. Many studies gave participants the nutrients as supplements rather than factoring them into the diet.

But there were no definitive answers from them, "despite the American publics penchant for a magic bullet," says Dr. William M. Vollmer, a senior investigator and statistician at Kaisers research center. Medical researchers guessed that different combinations of nutrients might affect blood pressure. After all, none of us eats only one food or nutrient at a time.

The $11.8 million DASH study, sponsored by the National Heart, Lung, and Blood Institute, examined that question - whether dietary patterns, not single nutrients, affect blood pressure.

The DASH-Sodium study showed that lower amounts of sodium made a big difference in blood pressure, and it led to creation of the Dash Diet (see accompanying chart).

Although both studies were coordinated by Kaiser in Portland, they enrolled participants in Baltimore, Boston, Baton Rouge, La., and Durham, N.C.

The 459 men and women participating in the first study were ages 23 to 75. Sixty percent were African Americans; in the general African American population, blood pressure rates are among the highest.

All of the participants had blood pressure readings above the ideal of 120/80 or below, but not high enough to require medication.

Participants followed the DASH Diet daily for eight weeks. The diet restricted saturated fat, and total fat accounted for only 28 percent of the

In general, Americans eat a diet in which 34 percent to 38 percent of the calories consumed are from fat. Researchers settled on 28 percent - certainly not the very low diet of 20 percent of calories from fat that is tough for most Americans to achieve.

But most important, people chowed down on four to five servings daily of both fruits and vegetables. (Before you blanch and say "No way!" at eating what seems like a truckload of roughage, remember that a serving is usually a half cup. You may be getting many more servings than you think.)

After eight weeks, researchers saw a "huge difference" as blood pressure readings dropped. "Clearly, it was not one nutrient," Vollmer notes, that made the difference. Best of all, there were significant drops within the first two weeks of the study.

In DASH-Sodium, salt was thrown into the research mix - and the results indicate that even those without higher blood pressure readings benefited from cutting back on sodium.

Americans get roughly 3,500 milligrams of sodium a day, mainly from processed foods, not just from the salt shaker. Sodium, naturally present at low levels in many foods, is added during processing.

When the 412 people in the DASH-Sodium study were restricted to only 1,500 milligrams of sodium, their blood pressure dropped more than that of the other participants. Of those, the participants who had had the highest blood pressure readings benefited the most. Thus, the Dash Diet recommends no more than 1,500 milligrams sodium daily - two-thirds the current limit of 1 teaspoon of salt

(2,400 milligrams sodium) suggested by health experts.

The big question remains: Can people use the DASH diet and make lifestyle changes like exercising more on their own to keep their blood pressure down?

A new study, Premier, will try to answer that when the results come out in about three years (see accompanying story). Roughly 800 participants are in Premier at four sites nationwide.

Most significantly, according to DASH dietitian Shirley R. Craddick of Kaiser, its results will help set national medical policy - the best ways to treat patients with high blood pressure and dispense practical advice to them.

The results may even guide the processed-food industry.

One way to reduce sodium may be to avoid processed foods. Instead of buying spaghetti sauce from a jar, Craddick advises, make it from fresh tomatoes. Njeri Karanja, a Kaiser center investigator with a Ph.D. in human nutrition, adds,

"Eat food as close to its natural form as possible.

"I dont think we need to be harping (for the food industry) to do this or that," Karanja says. "You make personal choices and the industry will respond." She points to McDonalds, which stopped buying genetically modified potatoes because consumers objected to this technology. (But as a side note, the chain still cooks with canola oil made from genetically modified rapeseed.)

In the meantime, most Americans might do themselves a favor by trying the DASH Diet, high in fruits and vegetables and low in sodium. "The DASH Diet" book will be published by Simon & Schuster Source this fall.

Some select groups - such as patients with kidney problems - should not try this diet without checking with their doctor.

Most important, if youre on blood pressure medicine, dont stop taking it.

Again, ask your doctor.

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