What amount of saturated fat is bad for the average person?

To understand what trans fat is, you first need a short primer on fats. Fats come in solid or liquid form and are a combination of saturated fat -- which is bad for your heart -- and unsaturated fat, which is not. Some fats are higher in saturated fat and others have more of the unsaturated variety.

Saturated fat, which raises cholesterol, is found in animal products -- think butter, whole milk, and steak -- and in troipical oils such as palm and coconut. Unsaturated fats, which can lower LDL (bad) cholesterol, are always liquid and found in vegetable oils. They come in two forms: monounsaturated (olive and canola oils) and polyunsaturated (safflower, sunflower, corn, and soybean oils). All fats are calorie dense, so eat even good ones in moderation.

No one knows how much trans fat a typical American eats -- estimates range from 2.6 grams to 12.8 grams per day, according to the American Heart Association -- or how much constitues a safe amount. In adjusting our diets, how low should we go? The Institute of Medicine of the National Academy of Sciences recommends that levels be kept as low as possible, as does the government's Dietary Guidelines for Americans.