Polyunsaturated vegetable oils, such as canola, corn or soy oils, become oxidized or rancid when heated. Consuming these oxidized oils can lead directly to vascular disease; therefore, these are not the oils one should be cooking with. Organic coconut oil is probably the healthiest oil to cook with because it is one of the least likely to oxidize when cooking at higher temperatures. We were told for years to cook with olive oil but it also can become oxidized when heated. Try to use it only if sautéing on low to moderate temperatures. Olive oil is actually best used unheated such as on salads. Try to use mostly coconut oil or olive oil, when needed, in your food preparation to obtain healthy fats. For some of you who just do not like the taste of coconut oil with certain foods when cooking with higher temperatures, “clarified” butter is another fat that withstands high heat. Just be practical and don’t use it too often. Go to any food website to learn how to clarify butter.
Most information came from Mercola.com.