When Good Fats Go Bad
Processing turns vegetable oil into what may be the worst fat of all.
Photography by Pornchai Mittongtare
Cereal, peanut butter, microwave popcorn, granola bars, flour tortillas, frozen waffles--these may sound like healthy, wholesome snacks. But many such prepared and processed foods have a dirty little secret: a health hazard called trans fatty acids, or trans fats.
Manufacturers love trans fats--which usually appear on labels under the guise of "partially hydrogenated vegetable oil"--because they help make packaged foods crunchy, crispy, and/or creamy and extend product shelf life at the same time. Yet the risk of TFAs to the heart may be even more serious than that posed by the saturated fats in meats, cheese, butter, and other animal products.
"We now have a large amount of scientific research documenting the association of trans-fat intake with heart disease," says Penny M. Kris-Etherton, Ph.D., professor of nutrition at Pennsylvania State University.
Weird Science
The genesis of trans fats started about 100 years ago, when manufacturers came up with the idea of turning inexpensive vegetable oils into solid fats that would function like more expensive butter or lard but have a longer shelf life. To achieve this alchemy, they figured out a way to add hydrogen atoms to unsaturated fatty acids in oils, enabling the oils to stay solid at room temperature. And so the process of hydrogenation was invented.
Soon the world had the first product made with hydrogenated fats: Crisco, introduced in 1911. But the chemical reaction involved produces a type of fatty acid with a twist in its chain of carbon atoms--a trans fatty acid.
Because of its unnatural shape, a trans fat behaves like a saturated fat, only worse. Both saturated fats and trans fats raise "bad" LDL cholesterol. But trans fats also lower "good" HDL cholesterol. This worsens the LDL-to-HDL ratio, a prime indicator of heart-disease risk. In addition, consuming trans fats increases levels of small, dense LDL cholesterol in the bloodstream; these particles enter arterial walls easily and promote the formation of artery-clogging plaque.
In an analysis of data collected in the 1980s during the large-scale Nurses' Health Study by the Harvard School of Public Health and Brigham and Women's Hospital in Boston, women with the highest intake of trans fatty acids had a 27 percent greater risk of heart disease than women with the lowest intake. In addition, researchers found that an increase of as little as 2 percent in TFAs resulted in a higher risk for type 2 diabetes; consuming polyunsaturated fats, such as safflower oil, reduced diabetes risk.
Guiding Light
In light of these findings, the government is including new trans fatty acid recommendations in the 2005 Dietary Guidelines for Americans set by the Department of Health and Human Services and the Department of Agriculture. The recommendation is to limit TFA intake to less than 1 percent of calories--that's just 2 grams per day for a 2,000-calorie diet. This is an ambitious goal, given that a single donut may contain more than 3 grams and a large order of french fries nearly 7 grams. Indeed, the average American's intake of trans fats is currently about 5.8 grams per day. (The numbers vary widely, from .5 gram or less for vegans to 10 grams or more for junk-food junkies.)
Managing your TFA intake will get easier starting in January 2006, when the FDA will require the number of trans-fat grams per serving to be listed on the Nutrition Facts panel of food labels. (Be aware, however, that when a product contains less than .5 gram of trans fats per serving, the manufacturer is permitted to list trans fats as grams.) Until then, your best way of knowing if a food contains trans fats is to find the words partially hydrogenated on the label.
You won't have far to look. More than 40,000 products contain these oils, especially commercial baked goods such as muffins, cookies, and crackers.
Trans Trimmers
Buy baked goods from your local bakery, which doesn't need to use hydrogenated oils to give its products a long shelf life. (To be sure, ask.) Trans fats occur naturally in animal products, so eat the leanest possible meats and go with reduced-fat dairy options. Stick margarine contains approximately 1.8 to 3.5 grams of trans fats per tablespoon, so switch to the tub form, which has about .4 to 1.6 grams, or choose a trans-fat-free vegetable oil spread. When eating out, skip fried items and order broiled or baked foods.
Better yet, cook your own meals and fill your plate with nutritious ingredients that never contained trans fats in the first place: fruits, vegetables, beans, nuts, and whole grains. You can ban trans fats from your diet and still have plenty of tasty options to enjoy--and we've provided four delicious TFA-free recipes to prove the point.
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