A fat or oil’s Smoke Point is the temperature at which wisps of smoke appear, signaling that the oil is breaking down from the heat. Cooking in oil past its Smoke Point gives food an off flavor and can be unhealthy because many of the fatty acids have been destroyed and free radicals (toxic molecules) have been created by the excessive heat.
In general, temperatures above 320˚F (160°C) cause Unsaturated Fats to form Trans Fat, a type of fat not normally present in oils that can clog arteries and increase the risk of cancer. Continued consumption of burnt oils can lead to atherosclerosis, inflammatory joint disease, and the development of birth defects.
Consider the smoke point of your fats when baking because temperature is the ultimate arbiter of a fat’s smoke point and baking a fat past where it will break down can be trouble too.