Health experts are making progress in their war on trans fat, the saturated fat that was heaped into much of the fast-food, baked goods and spreads consumed by far too many Americans. But these unhealthful fats are still out there, though in smaller quantities, and now there may be concern about products that are replacing them.

Research has shown a disturbing link between trans fatty acids and increased risk of cardiovascular disease. A study at Harvard found that eating just 5 grams of trans fat a day could increase the risk of heart disease by 25 percent. Researchers concluded that eliminating trans fat from the American diet could prevent nearly 228,000 heart attacks.

Virtually unheard of a decade ago, trans fat became the new villain of the health-conscious world. In 2006, the U.S. Food and Drug Administration (FDA) began requiring food manufacturers to list trans fat content greater than half a gram on nutrition facts label. Restaurants are not required to list their contents, but many of them (especially large fast-food chains) are voluntarily taking out or reducing the trans fat, at least in some products.

What are trans fats? They are substances produced when hydrogen is added to vegetable oil, a process called hydrogenation. This process makes some foods tastier and keeps them fresher longer on store shelves.

Trans fats have been used extensively in making cakes, pies and cookies and as the basis of many lards, spreads and solid cooking oils. You might think yummy, but there's a down side. Trans fats raise the low-density lipoprotein (LDL) blood levels in the body. That's the bad cholesterol responsible for clogging arteries and causing strokes and heart attacks. Trans fats also reduce the level of good cholesterol (HDL) in the blood. A double whammy.