Q: If you cook at a high heat with flaxseed oil does it oxidize and become bad for your arteries?
– Judy

A: While this is not my area of expertise, it is my understanding that when fats are overheated to their “smoke point” a part of the molecule begins to breakdown into a toxic substance called acrolein, which is volatile and highly irritating to mucous membranes and possibly arteries. Polyunsaturated fats are particularly susceptible to this process, so flaxseed oil, which is very polyunsaturated would be a prime target. Reusing the oil only makes matters worse (as in deep-fat frying). In addition, anytime you have heat, air, and fat, there are substances called free radicals (or oxidants) that are formed during cooking – process called oxidation. So a fried egg which is exposed to the air during cooking would contain more free radicals than a boiled egg still in its shell while being cooked. Excessively high heat would just speed up this process. Free radicals or oxidation are/is associated with numerous diseases, from heart disease and cancer to arthritis and reduced immunity.

The bottom line is: Don’t heat your cooking oil to the point that it smokes. There is no need to do that in good cooking and it could generate harmful substances. You also would destroy some of the properties of the flaxseed oil that are beneficial, so you would be defeating your purpose in using this expensive oil in the first place. Definitely DON’T reuse any oil that has already been used for cooking. – Elizabeth Somer