Butter, which has been around for thousands of years, is made from animal products. This makes it high in cholesterol and saturated fat, which have been linked to heart disease.
Margarine, on the other hand, is made from 'good' fats - polyunsaturated and monounsaturated vegetable oils. These types of fat help reduce low-density lipoprotein (LDL), or "bad," cholesterol, when substituted for saturated fat.
Most people assume that makes margarine heart-healthy. Well, not exactly. The process of turning polyunsaturated oils into semisolid table spreads creates trans fats, which are just as bad as saturated fats, if not actually worse. Like saturated fats, trans fats increase blood cholesterol and the risk of heart disease. In addition, trans fats can lower high-density lipoprotein (HDL), or "good," cholesterol levels.
When choosing a margarine, experts advise to try find one with the lowest trans fat content possible and less than 3 grams total of saturated plus trans fats. Manufacturers are now required to list saturated and trans fats separately on food labels. Many varieties of margarine now contain water or liquid vegetable oil instead of partially hydrogenated vegetable oil. This can make them virtually free of trans fats. Even better, experts say, is to choose an alternative, like olive or canola oil.
There are also bread spreads that contain phytosterols, natural plant compounds that have been shown to reduce LDL cholesterol levels by 6 percent to 15 percent when eaten in recommended amounts. So, butter your side of the bread keeping these facts in mind.