There is general agreement by now that trans fats increase the risk of heart disease by raising LDL cholesterol and lowering HDL cholesterol.

Legislation has been passed in some cities that prohibits restaurants from using trans fats, and such laws may eventually spread nationwide. But first, replacements must be found for these artery-clogging fats.

One easy switch is to use canola or soybean oil for frying some foods. But these oils cannot be used in the preparation of baked goods such as piecrusts, cookies, pastries, and pizza crusts. Another tempting approach is to substitute animal fats like butter or lard, but these contain mostly saturated fats, which are almost as bad for us as trans fats. Animal fats raise LDL cholesterol but do not lower HDL cholesterol.

So manufacturers are struggling to find healthy substitutes for trans fats while chefs and food chemists are checking the taste of other naturally occurring and chemically modified fats that can replace trans fats in these products.

Even when suitable substitutes are found, growing the necessary crops that contain these fats will take some time, as will determining whether the next generation of fats are really safer than animal fats or trans fats.

Meanwhile, don't be misled by food packaging that boasts a product is "trans fat-free" — you must read the label to find out which fat has replaced the trans fats.

A trans-fat-free margarine, for example, is still going to be composed almost entirely of fat. And if the trans fats have been replaced by saturated fats, such a margarine can hardly be called heart healthy.