I would like to know if the omega 3 ALA and omega 6 LA oils in vegetables, nuts and seeds are destroyed when cooked, and if so to what degree? I understand that refined sources of omega 3 should not be heated such as flax seed oil but I was wondering if there is any damage done with whole foods like vegetables or nuts and seeds when cooked.
Destroyed, no. Damaged, yes. But! All food degrades to some degree when cooked. Fats go rancid, carbohydrates burn/char and are chemically converted to various nasties, proteins also are chemically transformed into nitrosamines and such that cause disease.
Cooking food often does more good than bad, so do not fret too much. Best guideline is to simply not burn your food.
In general, fats degrade the most upon cooking (cmp to carbs and proteins). It not just PUFA, also MUFA and SFA. Solution: forego fried foods in particular and even sautéed foods. Eat baked, boiled, long simmered and raw foods. BBQ foods are probably OK. IMHO, the damage to fats in broth in particular is zero.
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