Updated on 3/31/2005
I don't keep butter in my own house, and I advise against using it regularly. I do, however, recommend butter over margarine, if that is the choice.
Butter is the most saturated of all the animal fats and contains the most cholesterol of all animal fat - more than twice that of beef fat! For cardiovascular health, it is a good idea to minimize consumption of butter and other sources of butterfat: cream, ice cream and whole milk products. Check labels carefully for the percentage of fat in all of them.
As I'm sure you know, diets high in saturated fats are associated with high cholesterol levels and the risk of coronary heart disease. Polyunsaturated fats found in vegetable oils lower cholesterol levels, but present dangers of their own. For example, margarine is made from liquid vegetable oils that are artificially saturated (with hydrogen) to make them semisolid. This process changes the fat molecules making them capable of damaging arteries and raising the risk for heart attack. I believe that these oils also promote cancer, inflammation, damage to the immune system and premature aging. Some of this harm is due to unnatural fat molecules (trans-fats) created in the hydrogenation process.
The monounsaturated fat found in olive oil and nuts is the healthiest fat of all and the type I recommend that you rely on the most. If you don't want too strong a flavor of olive oil, try one of the "light" brands or use a good, neutral-flavored oil such as grape seed oil.
I personally prefer olive oil for most of my cooking. If I had to choose between butter and margarine, I would choose butter, as I've said. Using small amounts of butter occasionally probably won't hurt you, but I wouldn't make a habit of it.
Andrew Weil, M.D.