New York ? There are plenty of things in Kentucky Fried Chicken that are bad for your health – cholesterol, saturated fat and salt, to name a few. But only one has the potential to get the colonel’s recipe banned in New York City.

That ingredient is artificial trans fatty acids, which are so common that the average American eats 4.7 pounds a year, according to the Food and Drug Administration. City health officials say these so-called trans fats are so unhealthy they belong in the same category as food spoiled by rodent droppings.

Today, the Board of Health will hold its first public hearing on a proposal to make New York the first U.S. city to ban restaurants from serving food containing artificial trans fats.

Eateries are scrambling for ways to get trans fats out of their food.

KFC Corp. said it was planning a “major announcement” in New York today about a change coming to all 5,500 of its U.S. restaurants. Franchise owners told several newspapers and magazines that KFC would stop using partially hydrogenated vegetable oil – the primary source of artificial trans fats.

Representatives of the company and its parent, Louisville, Ky.-based Yum Brands Inc., declined to comment, but the possible switch was applauded by the Center for Science in the Public Interest, which sued KFC in June over the trans fat content of its chicken.

“Assuming KFC goes through with it, it would be a tremendous improvement for the nutritional quality of their foods,” said the center’s executive director, Mike Jacobson.

McDonald's french fries have been cooked in partially hydrogenated vegetable oil since the company abandoned beef tallow in 1990. Today, New York City's Board of Health will hold its first public hearing on a plan to make New York the first U.S. city to ban restaurants from serving food containing artificial trans fats.

Invented in the early 1900s, partially hydrogenated vegetable oil was initially believed to be a healthy substitute for natural fats like butter or lard. It was also cheaper, performed better under high heat and had a longer shelf life. Today, it is used for deep frying and as a shortening in baked goods like cookies and crackers.

Ironically, many fast food companies became dependent on hydrogenated oil about 15 years ago when they were pressured by health groups to do something about saturated fat. McDonald’s emptied its fryers of beef tallow in 1990 and filled them with what was then thought to be “heart-healthy” partially hydrogenated vegetable oil.

Trans fats significantly raise the level of so-called “bad” cholesterol in the blood, clogging arteries and causing heart disease. Researchers at Harvard’s School of Public Health estimated that trans fats contribute to 30,000 U.S. deaths a year.

“This is something we’d like to dismiss from our food supply,” said Dr. Robert H. Eckel, immediate past president of the American Heart Assn.

Wendy’s, the national burger chain, already has switched to a zero-trans fat oil. McDonald’s announced in 2003 that it intended to do so but has yet to follow through.

If approved, New York’s ban would only affect restaurants, not grocery stores, and wouldn’t extend beyond the city limits. But experts said the city’s food service industry, with 24,600 establishments, is so large that any rule change is likely to ripple nationwide.

“It’s going to be the trendsetter for the entire country,” said Suzanne Vieira, director of the culinary nutrition program at Johnson & Wales University in Providence, R.I.