While margarine's appearance on supermarket shelves has literally been a lifesaver for the millions of Americans with high cholesterol, new research has revealed that there is still room for improvement. A study released in August from the Department of Human Nutrition at Agricultural University in The Netherlands showed that a portion of the fat in hardened vegetable oils, found in most margarines and shortenings and in packaged cookies and crackers, not only raised total blood cholesterol, but also lowered high-density lipoproteins (HDL), the "good cholesterol."
When polyunsaturated liquid oils are converted to solid fats in a process called hydrogenation, trans-unsaturated fatty acids, stearic acid and monounsaturated fatty acids are formed. It is the trans-unsaturated fatty acids that the Dutch researchers, Dr. Ronald P. Mensink and Dr. Martijn B. Katan, found to be almost as harmful to cholesterol levels as saturated fat. The other two components of margarine--stearic acid and monounsaturated fat--do not raise the cholesterol level. "These new findings do not mean that people should switch to butter instead of margarine," said Dr. Scott M. Grundy, director of the Center for Human Nutrition. "Butter is still more damaging to cholesterol levels than any margarine because butter has much more cholesterol-raising saturated fat."
Dr. Grundy is calling upon food manufacturers to alter the way they make margarines and shortenings by cutting down on trans-unsaturated fat and increasing other safer components He also is urging the Food and Drug Administration to revise package labels to more accurately reflect new research into dietary fats. He outlined his proposals in the editorial accompanying the Dutch report in the Aug. 16 issue of The New England Journal of Medicine.
Industry needs to provide the public with healthier alternatives, he said. "One way to reduce the content of trans fatty acids in margarines and shortenings is to blend several natural fats to achieve the desired texture. Alternatively, the content of stearic acid can be increased at the expense of trans fatty acids by more complete hydrogenation," Dr. Grundy wrote.
Although stearic acid, found in beef fat and cocoa butter, is a saturated fat, Dr. Grundy and his associates showed in 1988 that it does not raise cholesterol like other saturates. It apparently is quickly changed into healthier monounsaturated fat. Dr. Grundy said one reason manufacturers are reluctant to change to stearic acid is that the U.S. Food and Drug Administration requires it to be labeled as a saturated fat. This might scare off some consumers who try to avoid saturated fats, which generally raise cholesterol levels. "The labeling scheme of fats needs to be changed," Dr. Grundy wrote. "It is no longer justifiable to identify saturated fatty acid as the dietary culprit responsible for raising LDL (low-density lipoprotein) cholesterol levels.
Instead, the various culpable acids should be grouped together as cholesterol-raising fatty acids, a group which includes trans-unsaturated fatty acids." The Dutch researchers estimate the average daily intake of trans fatty acids in the United States to be 8 to 10 grams, or 6 to 8 percent of total daily fat consumption. They suggest that eliminating all trans fatty acids from the diet might increase the level of HDL cholesterol by 2 milligrams per deciliter and decrease the level of LDL cholesterol by 4 mg/dL.
"Superficially," Dr. Grundy said, "trans fatty acids may appear to be of little importance because the diet contains relatively small amounts; however, the large quantities of all cholesterol-raising fatty acids consumed in the United States do not come from one or two sources but from a variety of foods. If a substantial reduction in the consumption of cholesterol-raising fatty acids is to be achieved, intake of all foods containing fat with a high proportion of trans fatty acids and food containing saturated fats must be curtailed."
