Polyunsaturated oils, which include vegetable oils like corn, soy, linola and canola are beneficial on their own. However, by making them into cooking oils, they are heavily refined and processed, rendering them rancid and toxic. For a long time now, these cooking oils have been mistakenly regarded as the “healthier” choice, but experts have now pointed out that this is a fatal mistake.
After refining and processing, these beneficial oils become oxidized as they get exposed to heat from the processing, resulting in the formation of trans-fat and damaging free radicals (this is a process called hydrogenation).
The truth is, coconut oil which have been regarded as unhealthy is the better choice for cooking. Unlike most unsaturated oils, coconut oil does not turn toxic when cooked.
Other alternatives are virgin (or extra virgin) olive oil for light cooking or sauteing, or grapeseed oil for high heat cooking.