If I am going to cook with oil, which is the best to use, and why are certain ones problematic?
Oils that are best to use for high heat cooking include those with higher smoke points. These would include high-oleic safflower oil (smoke point: 450ºF/232ºC), high-oleic sunflower oil (smoke point: 450ºF/232ºC), avocado oil (smoke point: 520ºF/271ºC), or refined coconut oil (smoke point: 450ºF/232ºC). Also, you may consider ghee, which has a smoke point of 400˚-500˚F (204˚-260˚C).
As you'll note, the only oil we include on our website is extra virgin olive oil. At the heart of the Mediterranean diet, extra virgin olive oil is rich in monounsaturated fats and polyphenol antioxidants and has found to be heart healthy. Yet, we don't like to cook with extra virgin olive oil (the highest we'll cook with it is up to 250˚F121˚C, which is fine for making sauces or heating up a dish but not high enough for sautéing).
The reason we don't like to heat extra virgin olive oil to higher temperatures is because it has a lower smoke point than the other oils mentioned. All vegetable oils are susceptible to heat damage-much more so than the whole foods from which they were pressed or extracted. But in the case of extra virgin olive oil, the susceptibility is especially great, notably in the destruction of its polyphenolic phytonutrients. Extra virgin olive oil has such a great flavor let alone an amazingly rich nutrient profile that we want to preserve so we don't like to cook with it but rather enjoy it as a salad dressing or drizzled on foods after they have been cooked.