This is an important topic and a serious reader will research it beyond what I have to say here.  The bottom line is that I use only certain fats in limited quantity  (organic butter, olive oil, coconut oil, flax seed oil, hemp oil).  I avoid all saturated, trans fats, and hydrogenated fats.   I have learned that:

• Omega 3 and omega 6 fatty acids are called “essential” because the human body cannot make them.
• The balance of Omega 3 and Omega 6 fatty acids is extremely important.  In Anti-Cancer, Servan-Schreiber says the quantity of omega 3s and omega 6s stems directly from the content of the food we eat and what the cows and chickens we eat have consumed.  It turns out that it is this dietary balance that has changed the most in the last 50 years. This ratio can be measured in a blood test.  In June, my ratio was 8.4   down from 13.3 six months earlier.

• Good fats are essential to good health.  Omega 3 fatty acids are mono unsaturated fats.   Examples are coconut oil and olive oil. Omega 3 fatty acids are found in small fish, such as sardines and salmon, nuts and seeds.
• Most of the American diet today is comprised of Omega 6 fat.  Omega 6 oils altered to become solid at room temperature are saturated fats, trans fats, hydrogenated and partially hydrogenated fats.  As mentioned in a previous post, food makers are motivated by profit and these fats do not go stale.  They have a longer shelf life.  Examples are margarine, Crisco, corn oil, vegetable oil, sunflower oil, soybean oil, and canola oil.

For more information:

http://www.livestrong.com/article/26035-list-omega-foods/

http://www.whfoods.com/genpage.php?tname=nutrient&dbid=84