Q: What's the difference between extra virgin, virgin, and cold press olive oil?

A: For many years now, I've recommended people substitute olive oil (a monounsaturated fat) for butter, margarine, and other oils. Aside from being a satisfying fat alternative, olive oil offers unique health benefits -- it appears to protect against both cancer and heart disease (by increasing blood levels of HDL, the "good" cholesterol), and it has antioxidant activity. Buying olive oil, however, can be a confusing proposition. Unlike vegetable oils, there are many different types to choose from.

The best olive oil is made of a mixture of olives which are "cold pressed." (The oil is extracted from an application of pressure -- no chemicals are involved.) Olive oil made by the cold-pressing method is lower in acidity, probably the most important measure of olive oil quality. Of course, the color, flavor, and aroma are important, too. Here's an explanation of the various types of olive oil:

• Extra virgin: This comes from the first pressing of olives. Extra virgin oil is lowest in acidity (one percent) and is considered the finest, fruitiest type of olive oil. Not surprisingly, it is also the most costly. The color of extra virgin oil ranges from a pale yellow to bright green. Usually, the deeper the color, the more intense is the flavor. Use extra virgin oil for salad dressings or instead of butter for dipping bread at the table. Of course, you can use it for everything else, too.
• Virgin: This is a first press oil, but the acidity is slightly higher than extra virgin (about 3 percent).
• Fino (Italian for "fine" ): A blend of extra virgin and virgin oils.
• Light: The lightest in color of any kind of olive oil, light oil has no distinctive taste and is recommended for baking or cooking when you don't want an olive oil flavor. Although it is tasteless, it has the same amount of beneficial monounsaturated fats as other types of olive oil, But as a result of the refining process, loses some of the healthful qualities of unrefined types.

As far as prices are concerned, in very general terms, expensive olive oils tend to be more flavorful. I'd advise against buying large bottles (or cans) of olive oil -- once open, you should only keep olive oil for about six months. Store it in an airtight container.