Christina M. Stark, MS, RD, CDN Responds:

Christina Stark, MS, RD, a nutrition specialist in the division of nutritional sciences at Cornell University, responds: Margarine has long been considered a better alternative than butter. Then studies began to suggest that the type of fat found in margarine might not be as healthful as earlier thought. This caused confusion, and many people assumed they should switch back to butter.

Butter contains mostly saturated fat, which increases LDL (bad) cholesterol, and thus the risk of heart disease. When margarine was developed as an alternative to butter, it contained a high level of trans fatty acids, or trans fat. The confusion about the healthier choice began when researchers discovered that trans fat not only increases LDL cholesterol, but also decreases HDL (good) cholesterol. In short, trans fat, like saturated fat, was found to increase the risk of heart disease. Today most experts believe the key is to watch the type of fat and the amount you're consuming. Polyunsaturated and monounsaturated fats are preferred to saturated or trans fats, and health experts still agree that less than 30% of daily calories should come from fat. As of January 1, 2006, FDA requires all food manufacturers to list the amount of trans fat on the nutrition labels of foods. (The amount of saturated fat has long been required.) This will make it much easier to minimize both saturated and trans fat in your diet. So what's the bottom line?

Some would suggest the healthiest solution is to switch from butter or margarine to mostly polyunsaturated and monounsaturated fats such as those in soybean, olive, and canola oils. Others point to nonstick cooking spray as a healthy alternative when preparing food. If you choose to stick with margarine, here's a hint: Soft or liquid versions are likely to contain less trans fat than solid margarines, though now there are many brands on the market that are free of trans fat. Butter and regular margarine have the same amount of total fat and calories per tablespoon. Cutting back on both helps you reduce saturated fat, trans fat, and total calories from fat—which is a good choice for your body.