Which fats are healthful and which are unhealthful?

Fat is classified into saturated fats, polyunsaturated fats, and monounsaturated fats.

Saturated fats appear to increase your risk for heart attacks when you take in more calories than you burn.

Monounsaturated fats are considered healthful because they form LDL cholesterol that is resistant to oxidation; plaques are formed by oxidized LDL. Good sources include olive oil and avocados.

We used to think that all polyunsaturated fats help to prevent heart attacks when they replace saturated fats, but now we have different information. Polyunsaturated fats are classified by their structures into omega-3s and omega-6s, and you need both types; these are called the essential fatty acids because you cannot make them in your body and must get them from your food.

For most of the time humans have been on earth we have eaten foods that contain omega-6's and omega-3's in a ratio of about 2:1. However, over the last 50 years in North America, the ratio has changed; it now ranges from 10:1 to 20:1. Today our diet includes huge amounts of oils that are extracted from plants and used for cooking or in prepared foods. These oils (such as corn oil, safflower oil, cottonseed oil, peanut oil, soybean oil) are primarily omega-6s. We have decreased our intake of omega-3's, found primarily in whole grains, beans and other seeds, and seafood. Eating too much omega-6 and too little omega-3 causes clots and constricts arteries to increase risk for heart attacks, increases swelling to worsen arthritis, and aggravates a skin disease called psoriasis. It may block a person’s ability to respond to insulin, causing high insulin and blood sugar levels and obesity. It increases hormone levels of insulin like growth factor-1 that causes certain cancers.

To get your ratio on omega-6s to omega-3s back to a more healthful 2:1, eat seafood, whole grains, beans and other seeds, and reduce your intake of foods made with or cooked in vegetable oils.

The most unhealthful fats are the polyunsaturated oils that have been processed to form trans fats (partially hydrogenated vegetable oils)

Dr. Gabe Mirkin's Fitness and Health E-Zine
September 25, 2005