"Study Rates Stick Margarine as Unhealthiest," read the headline in a major newspaper a few weeks ago. It was referring to butter vs. margarine research led by Alice H. Lichtenstein, a heart disease scientist at the USDA Human Nutrition Research Center at Tufts University. But the headline "got it wrong," says Lichtenstein. "An argument about whether stick margarine is preferable to butter or vice versa is totally irrelevant. The point is that both are less preferable than all the other alternatives on the market," by which she means plain cooking oil, semiliquid margarines that you can squeeze out of a tube, and soft, spreadable margarines in tubs.

Alberto Ascherio, an epidemiologist at the Harvard School of Public Health, disagreed in a review paper that was published with Lichtenstein's research in the New England Journal of Medicine last month. He has no quibble with the argument that butter and the stick margarine used in her research are less healthful than all the other options available. But he feels the stick margarine proved to be the worst choice of all.

Why can't nutrition researchers get together on this "smear" campaign?

It comes down to which they think is more likely to result in heart disease: saturated fat, which is found in the highest levels in butter, or trans fatty acids, most abundant in stick margarine.

Saturated fat raises "bad," artery-clogging LDL cholesterol more than trans fatty acids. Not surprisingly, the saturated-fat-laden butter raised LDL cholesterol more than any other spread in Lichtenstein's study, as it has in others. Trans fatty acids, created when manufacturers harden oils to make, for instance, stick margarine, raise LDL cholesterol, too, but not as much as saturated fat. However, they also lower "good," HDL cholesterol, which works to keep arteries clear and thereby facilitates blood flow. As in other research, the stick margarine in Lichtenstein's study lowered HDL cholesterol more than any other spread, thereby creating the least favorable proportion of HDL in relation to total blood cholesterol. And therein lies the heart of the disagreement.

Ascherio says there are "plenty of epidemiologic data" showing that an undesirable ratio of "good" cholesterol to other types of cholesterol in the blood is a better predictor of future coronary heart disease than simply high LDL cholesterol levels, and that's why he believes stick margarine with lots of trans fatty acids is the worst choice.

But Lichtenstein maintains that the epidemiologic findings aren't conclusive and that "no one knows" which of the two spreads is more likely to lead to a heart attack or other heart disease. "We don't have an answer yet on whether ratios of one type of blood cholesterol to another are more or less important than LDL levels by themselves," she says. For that reason, she comments, you can't say that trans fatty acids are worse than saturated fat or, to put it into food terms, that hardened margarine is worse than butter.

Okay, while the scientists continue to duke it out on that point, what are consumers supposed to do? First, remember that those on both sides of the great margarine-butter divide recommend choosing soft spreads--and oils over spreads--whenever possible. The softer the fat (oil is fat in liquid form), the less it will tend to have of both saturated fat and trans fatty acids.

Second, and even more important, keep in mind that the question of butter vs. margarine should not be the front and center concern for those making a conscious effort to eat a heart-healthy diet. Those spreads amount to a small amount of the fatty calories we eat overall. The biggest contributors of saturated fat to the American diet are meat and whole-milk dairy foods, of which butter is only one. The biggest contributors of trans fatty acids are baked goods, fried fast foods and prepared foods, such as candy bars, crackers and other packaged items. The trans fatty acids in margarine, in fact, make up only a quarter to a third of the trans fatty acids we eat.

When Lichtenstein began her study, all stick margarine was high in trans fatty acids. Now, some stick margarines are available that have no trans fatty acids (and tout that fact on their labels).

Indeed, while trans fatty acids make up about 2 percent of Americans' calorie intake on average, some people are consuming much more because of their overall dietary pattern--but not because of a preference for margarine. For someone who eats 1,800 calories a day, for instance, a doughnut for breakfast and a large order of fries at lunch comes to 5 percent of total calories as trans fatty acids, according to Ascherio's paper. And some people consume up to 8 percent of their calories as trans fats, he notes. Add that to the 12 to 13 percent of calories that Americans are eating as saturated fat (which is supposed to make up less than 10 percent of our calories), and you've got a diet that's really hard on the heart.

"We really have to put this whole area into perspective," Lichtenstein says. "Before you worry about butter versus margarine or even about which type of fat you're eating more of, the first order of business," she comments, is for people to take a broad view of their eating habits across the board. "They should ask themselves whether they are having at least five servings of fruits and vegetables every day--and I don't mean french fries," she notes.

If you're eating a largely plant-based diet that includes not just produce but also grains (including some whole grains), you have a better chance of not going overboard on saturated fat or trans fatty acids.

If your diet is made up largely of high-fat animal products such as burgers and fatty cuts of meat, full-fat dairy foods such as whole milk, ice cream and full-fat cheeses--and if it also has lots of fast foods and processed foods, including everything from candy bars to crackers to baked goods--fussing over whether the fat you're eating is saturated or trans from butter or margarine is getting way ahead of yourself.

Labels Offer Clues to the Fats Inside

Look at any packaged food, and the "Nutrition Facts" label will tell you how many grams of saturated fat it contains. What it won't tell you is how many grams it contains of trans fatty acids--the kind that not only raise so-called bad cholesterol in the bloodstream but lower "good" cholesterol. That information is not required.

Researchers on both sides of the butter-margarine debate believe it's time to require food manufacturers to list trans fatty acids as a separate entity or lump them together with saturated fat. In the meantime, look on the ingredients list. If it contains the words "hydrogenated oil" or "partially hydrogenated oil," you can be sure trans fatty acids are in the product, whether it's crackers, candy bars, boxed cakes, TV dinners or other foods.

A diet low in trans fatty acids and saturated fat is the ultimate heart-healthy goal, experts say. Both fats are virtually absent from fruits, vegetables, grain-based foods like bread, pasta and minimally processed cereals, and nonfat dairy foods. Lean meats, skinless poultry and fish have relatively small amounts.