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July 12 2007 12:00 AM

Nearly 10 years after public interest groups first petitioned for change, the Food and Drug Administration now requires food manufacturers to spell out for consumers how much trans fat is in the foods they are buying. Since January 1, 2006, food companies have had to include trans fat content on their nutrition labels.


The new regulations are a compromise between food companies, which had argued against listing trans fat grams, and consumer advocates, who had petitioned for the labeling and the establishment of a daily recommended trans fat allowance. The FDA failed to find a standard but has long acknowledged that the fats -- also known as trans fatty acids -- have a remarkable potential to clog arteries. Many people continue to eat large amounts of trans fats without knowing it. But with or without the labels, we should all take steps to limit this fat in our diets.


What are trans fats?

Almost all of the trans fats in our diet are artificial. They're produced when liquid vegetable oils are mixed with hydrogen and heated in a process called partial hydrogenation. (Trans fats are also made when food ferments in the digestive tract of cows, so small amounts of the fats show up in beef and non-skim dairy products.)


Trans fats are unsaturated, meaning they aren't completely packed with hydrogen, but they are twisted in a way rarely seen in nature. Their unusual structure allows them to pack tightly together, which is why shortenings and margarines made with trans fats are solid at room temperature.


How dangerous are trans fats?

You've always heard that unsaturated fats are relatively healthy compared to saturated fats. Trans fats are the exception to the rule.


According to the American Heart Association, trans fats can damage the healthy balance of a person's cholesterol levels. Like saturated fats, trans fats boost LDL, or "bad" cholesterol. This is the type that can clog arteries and cause atherosclerosis and coronary heart disease. But that's only half of the story. Trans fats also reduce the levels of HDL cholesterol, the "good" cholesterol that helps keep arteries clear.


According to a report from Harvard University, this two-pronged assault makes trans fats roughly twice as dangerous as saturated fats. In 1994, Harvard researchers estimated that trans fats cause almost 30,000 premature deaths from coronary heart disease in the United States each year, although some scientists have disputed this figure.


Where are trans fats found?

Stick margarine and vegetable shortenings owe their texture to trans fats. And because fast food restaurants use partially hydrogenated vegetable oil for deep frying, french fries and other fried foods are often loaded with trans fats. (McDonald's recently reduced -- but didn't eliminate -- the amount of trans fat in their fries by switching to a different type of oil.) Trans fats are also found in many commercial baked goods like crackers, cookies, muffins, and pastries.


What took the FDA so long?

The FDA had trouble deciding exactly how trans fats should be labeled. The first plan was to list a percentage daily value, as is done with fat and saturated fat. But what should the recommended allowance of trans fat be? The National Academy of Sciences launched an in-depth study to answer the question. In a report released in July 2002, the NAS concluded that any amount of trans fats is more dangerous than none at all, so it couldn't determine a recommended allowance.


In June 2006, the American Heart Association weighed in with new guidelines on saturated fat and trans fat consumption. In the new guidelines, the Association lowered the recommended amount of saturated fat you should eat from less than 10 percent to less than 7 percent. It also established a limit on trans fat to less than 1 percent of the total calories you consume.


Does this mean you should try to excise trans fats from your diet completely? The FDA says no. To do that, you'd have to eliminate dairy products and meats containing fatty acids, which experts say could result in your not getting enough of the nutrients you need to stay healthy.


What you should do, says the FDA, is limit the amount of trans fat in your diet -- and the new label should help you do that. The label will show the number of trans fat grams in the product, right under the listing for saturated fat. (While other ingredients on the label show a percentage of daily value, trans fat will not, since no daily recommended allowance has been determined.)


According to the FDA, it takes about three years before lower LDL cholesterol levels result in a reduced risk of coronary heart disease. Based on this, the agency estimates that three years after the new labeling goes into effect and consumers are more savvy about trans fats, we'll see 600 to 1,200 fewer cases of coronary heart disease and 250 to 500 fewer deaths a year in this country.


What can I do now to limit trans fats?

According to the American Heart Association, a low-fat diet offers strong protection against trans fats. If you're already sticking to AHA guidelines and getting less than 30 percent of your calories from fat and less than 7 percent from saturated fat, you probably don't have to worry much about trans fats.


But if you're like most Americans, you'll need to take a closer look at what you eat. If doughnuts, french fries, store-bought muffins, and cookies are staples of your diet, it's time to cut back. Even before trans fats are listed on labels, a little reading will still go a long way. If the label lists hydrogenated or partially hydrogenated vegetable oil as a major ingredient, the product is bound to contain trans fats. When possible, choose foods made with naturally unhydrogenated oils such as canola or olive oil.


A quick word about the ongoing butter versus margarine debate: Because stick margarine contains trans fats, some people assume butter must be a healthier alternative. But butter also contains trans fats, not to mention loads of saturated fats. The American Heart Association recommends using soft margarines sold in tubs and bottles. The margarine should have no more than 2 grams of fat per tablespoon, and should have liquid vegetable oil as the main ingredient.


Trans fats may be out of sight for now, but they shouldn't be far from your mind. By watching your diet, you can avoid this hidden threat. You may miss out on a few doughnuts, but the health rewards are worth it.


Chris Woolston, M.S., is a health and medical writer with a master's degree in biology. He is a contributing editor at Consumer Health Interactive, and was the staff writer at Hippocrates, a magazine for physicians. He has also covered science issues for Time Inc. Health, WebMD, and the Chronicle of Higher Education. His reporting on occupational health earned him an award from the northern California Society of Professional Journalists.


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