Is a Low-Fat Diet Risky?

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What's wrong with this picture? Quite a lot, argues Dr. Scott Grundy of the University of Texas Southwestern Medical Center, an expert on the role of fat in heart disease. For starters, he says, there is no reason to believe that essential-fatty-acid deficiency is widespread. On average, Americans consume more of these fatty acids than their bodies require -- and that could be a problem. In laboratory animals, too much polyunsaturated fat has been linked to suppression of the immune system and the growth of malignant tumors. There is even reason to suspect that fatty acids derived from polyunsaturated oils might contribute to heart disease. Why? Fatty acids are components of the molecules that transport cholesterol around the body. But these acids are sometimes converted, scientists believe, into a form that may trigger the process of atherosclerosis. Polyunsaturated compounds, it turns out, are particularly prone to this sort of alteration.

So maybe people shouldn't swill soybean-oil cocktails just because of the Boston University report. "Give me a break," exclaims Dr. William Castelli, director of the Framingham Heart Study in Massachusetts. "This was a very, very tiny study." The observation that heart-disease patients have low levels of essential fatty acids is interesting and deserves follow-up, but it hardly provides proof of cause and effect. In time, perhaps, a more convincing link will emerge.

Meanwhile, all those aging couch potatoes concerned about their heart might as well tune out the cacophony of opinions that results from incomplete knowledge and focus on a few unchanging verities. The reputations of margarine and soybean oil may rise and fall many times over. But butter is still bad. Fruits and vegetables are still good. And most scientists still agree that Americans eat too much fat of all kinds.