The average American diet contains about 35 percent to 40percent of calories from fat. Not all of this fat is bad--in fact, some types of fat have a beneficial effect on blood lipids and may lower the risk of developing coronary heart disease or dying of it. But the prevalent type of fat in the American diet is saturated fat, the major dietary factor that raises blood cholesterol levels. In fact, saturated fat has a bigger impact on blood cholesterol levels than dietary cholesterol itself. Saturated fat includes mostanimal and dairy fats and some oils, such as palm and coconut oils. The simplest dietary measure to lower the risk of CHD and heart attack is limiting saturated-fat intake. The 2001 National Cholesterol Education Program guidelines recommend reducing total fat to between 25percent and 35percent of total calories and limiting the intake of saturated fat to less than 10percent of total calories in order to reduce blood cholesterol levels--specifically LDL cholesterol.

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The guidelines also recommend limiting dietary cholesterol to less than 300 mg per day. But if LDL cholesterol levels remain high, saturated fat should be further restricted to less than 7percent of calories, and cholesterol to less than 200 mg per day.

When fat is consumed, monounsaturated fats should be chosen whenever possible.Olive and canola oils, almonds, and avocados contain large amounts of monounsaturated fat. Polyunsaturated fats--found in safflower, sunflower, and corn oils--also lower LDL cholesterol levels.

Omega-3 fatty acids, another type of polyunsaturated fat, seem to have cardioprotective benefits beyond LDL cholesterol lowering. Of the three types of omega-3 fatty acids, two are found only infish (particularly fatty fish. These can reduce the tendency for blood to clot, decrease the risk of arrhythmias (abnormal heart rhythms), and lower triglyceride levels. The American Heart Association recommends consuming at least two servings of fish per week to benefit from the cardioprotective effects of omega-3 fatty acids.

Just as with saturated fats, people should minimize their intake of trans fats, such as margarine or partially hydrogenated oils. Indeed, the Institute of Medicine, a branch of the National Academy of Sciences, recommends that trans fat consumption be as low as possible.