Canola oil stinks.
Its omega 3/6 ratio isn’t as bad as with other vegetable oils, and this is the only good thing about canola oil.
Let’s think about the structure of the molecules- what are monounsaturated (olive oil), polyunsaturated (vegetable oils), and saturated fats (butter, lard, coconut oil)? Saturated means the molecules are saturated with hydrogen, making the structure very stable. Mono has one hydrogen bond; polyunsaturated have two or more. Mono and poly are weaker - have you noticed how good olive oil (a monounsaturated fat) comes in a dark bottle? That’s because sunlight alone can break down the molecule.
When the molecules break down, it creates new molecules that are toxic, so we want to avoid this.
When you cook with canola or olive oil, they can certainly break down. You can look up information about smoke points, but in general you don’t want to cook with these on high heat. Medium-low heat should be okay, higher if you’re cooking with water.
But wait, there’s more. During processing, canola oil is in fact subjected to high heat- as high as 1200 degress F (think about what it takes to squeeze oil out of a vegetable. It’s not that easy, so they press it under high heat). What do you think happens? The molecules break down. The oil actually has to go through a deodorification process to get rid of the smell at the end of processing. This is disgusting.
Olive oil doesn’t have this problem - good olive oils are always cold pressed, so they don’t go bad. Olive oil is great.
When cooking at high heat, we should use saturated fats. They are much safer. These include butter, lard (preferably home made because the processed ones are traditionally loaded with trans fats), and coconut oil. People have been cooking with these for milennia; they are natural, whole foods and they are not the cause of heart problems. We need to get over our hangup on saturated fats. Look up the research of Weston Price to examine traditional peoples thriving on diets heavy in saturated fats- fascinating stuff. Clearly the omega 3 / omega 6 situation has a much greater impact than the saturated / unsaturated fat situation. Omega 6’s cause the inflammation that can lead to heart problems.
Here’s the vegetable oil article I wrote a while ago - http://newfoodview.wordpress.com/2008/11/30/whats-the-deal-with-vegetable-oil/