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This article is from the WebMD News Archive
Trans Fats Tops List of Heart Unhealthy Foods
July 13, 2001 -- Before you start dunking that donut or licking the filling out of your favorite sandwich cookie, consider this: That treat you love probably contains trans fats, which not only affect your cholesterol levels, but also may harm the functioning of your blood vessels. This dangerous combination may increase atherosclerosis, the hardening of your arteries.
A diet high in trans fats appears to be unhealthier than a diet that's "just high in saturated fats," Nicole M. de Roos, MSc, a researcher at Wageningen University in the Netherlands, tells WebMD. She says that compared with a diet high in saturated fats, a diet high in trans fats can reduce normal blood vessel function by nearly one-third and reduce HDL cholesterol -- the so-called good cholesterol -- by more than 20%. Poor blood vessel function, when the vessels fail to expand or dilate properly, is a risk factor for heart attack and stroke.
Processing of vegetable oils such as corn or soybean oil creates trans fats. The process forces hydrogen into the oils so that at room temperature the product is solid not liquid. By hydrogenating the oil this way it become less perishable. That means that products prepared with hydrogenated oils have a longer shelf life, which is why restaurants use hydrogenated oils for frying, and the donuts, cereals, cookies, and crackers that line supermarket shelves are prepared with hydrogenated or partially hydrogenated oils.
In the study, which is published in the July issue of Atherosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association, 29 healthy men and women consumed a diet high in trans fats or high in saturated fats.
On the high trans fat diet, volunteers used a specially made margarine that cannot be purchased in any store. That special margarine was very high in fat -- almost 10% of the daily calories came from trans fat. "That would be the equivalent of about five donuts a day," says de Roos.
Saturated fat comes from animal products or certain oils, such as palm or coconut oil. The study participants on the high saturated fat diet used a margarine that was made with palm kernel oil.
After four weeks on the assigned diet, researchers measured blood vessel function and cholesterol in each person. Then all the volunteers crossed over and ate the other diet.
After four weeks on the second diet, the researchers again measured blood vessel function and cholesterol.
Alice H. Lichtenstein, DSc, professor of nutrition at Tufts University in Boston, tells WebMD that the study is interesting but "artificial." Lichtenstein, who is vice chair of the American Heart Association's nutrition committee, says that only about 2% of the fats consumed by Americans are trans fats, while as much as 12-14% of fat intake is from saturated fats. Keeping the emphasis on "reducing saturated fat intake" makes the most practical sense, she says.
The American Heart Association recommends limiting saturated fat intake to no more than 10% of total calories and limiting calories from fat to 30% of total calories.
"The very best advice is to focus first on increasing fruit, vegetable, and whole grain intake, " says Lichtenstein. "Cut down on meat and dairy products -- just lean meat and poultry."
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