Oils to Avoid:
First and foremost, try to buy certified organic oil to avoid negative effects of genetically engineered organisms. Also, steer clear of oils that have been bleached, deodorized, refined, or hydrogenated.
Additionally, anytime you cook a food, you run the risk of creating heat-induced damage. The oils you choose to cook with must be stable enough to resist chemical changes when heated to high temperatures, or you run the risk of damaging your health. As the oil is heated and mixed with oxygen, it goes rancid. Rancid oil is oxidized oil and should not be consumed—it leads directly to vascular disease. You should avoid GMO vegetable oils such as canola, corn, and soybean oil.