One of the main things to consider when evaluating whether it is OK to heat any oil for cooking is the smoke point of the oil. The smoke point is the temperature at which visible gaseous vapor from the heating of oil becomes evident. It is traditionally used as a marker for when decomposition of oil begins to take place. Since decomposition incurs chemical changes that may not only result in reduced flavor and nutritional value but also the generation of harmful cancer causing compounds (oxygen radicals) that are harmful to your health, it is important to not heat oil past its smoke point. Inhaling the vapors can also be damaging.

The following table presents smoke points of various fats:

Choosing Ghee, Mustard Oil, Rice Bran, Safflower oil and Extra Light Olive oil are some preferred options when it comes to frying.  Avoid heating any oils unto their smoke points.