Everybody knows that fat is bad for you. Right?

Well, not exactly. It is fat that has been most unjustly demonized. We have been suffering from a low fat craze for the last twenty years. Everybody (well not really everyone!) has been convinced that fat is bad for us and should be avoided at all costs. So what has happened? We got fatter! Obesity rates are going through the roof.

So yes, we need fats. They make up cell membranes and hormones, are required for absorption of the fat soluble vitamins (A, D, E, and K), are critical for infant brain development and the female reproductive system, and provide energy. Ever wonder why everyone seems to have a Vitamin D deficiency these days? Perhaps because they are not consuming the right fats for Vitamin D metabolism.

There are two types of fats – saturated and unsaturated (further defined as monounsaturated and polyunsaturated). One of the easiest ways to tell them apart is that saturated fats are solid while unsaturated fats are liquid at room temperature. Unsaturated fats are much more sensitive to oxygen, light and heat.

This sensitivity underlies the critical nature of fat you need to understand. When fats are heated or exposed to excess light and oxygen they oxidize. It is dangerous when we consume oxidized fats. Oxidation leads to inflammation which damages cells and is linked to a variety of diseases including heart disease.

Saturated fats are able to withstand greater temperatures before oxidation occurs. The most susceptible fats to oxidation are the unsaturated fats, particularly the polyunsaturated ones such as vegetable oil, corn oil, soybean oil, canola oil, and cottonseed oil. Note that margarine is made from various combinations of these oils.

Therefore, when cooking with fats and oils we want to use saturated fats such as butter, clarified butter (ghee), or coconut oil. For salad dressing or other room temperature uses olive oil is best.

Another fat we hear of are trans-fatty acids. These are formed during the process of hydrogenation. Hydrogenation is used to “stabilize” vegetable oils so they will not oxidize and was initially developed to lengthen shelf life of processed foods.

In the hydrogenation process polyunsaturated oils, usually corn, soybean, safflower, or canola, are heated to high temperatures and injected with hydrogen atoms. During the heating process the nutrients in the oils are destroyed, the oils become solid and have oxidized.

Trans-fats have been linked to many ailments, including cancer, heart disease, and reproductive problems. Trans-fats are commonly found in commercial baked goods, cookies, crackers, margarines, vegetable shortenings, and processed dairy products.

What fats should I eat?

Your sources of healthy fat include: butter (and please use organic butter); extra virgin olive oil, virgin coconut oil, fish oils, fresh flaxseed oil or ground flax seeds; and chia seeds.

Additional sources of healthy fats, although best to practice balance and moderation of these foods: eggs; nuts and seeds such as almonds, cashews, walnuts, pumpkin seeds, sunflower seeds, etc. (Please note that nuts and seeds are best raw and then dehydrated); dairy foods such as cheese, cottage cheese, and yogurt without added sugar (I recommend that all dairy be organic).

Avoid the following foods as they contain trans-fats and oxidized oils: margarine (yes, even the “smart” products); vegetable oil; corn oil; soybean oil; canola oil; safflower oil; and sunflower oil.

Bernard Rosen, PhD is a Nutrition Consultant and Educator. He works with individuals, groups, and at corporations to create individualized nutrition and wellness programs. His office is in Mequon, WI. To learn more or to schedule an appointment, e-mail at bernie@brwellness.com, call (262) 389-9907 or go to www.brwellness.com.