"don't heat it much"
your body is almost 40C... PUFAs might take a lot longer to oxidize at that temperature than 200C but how long is it inside your body?
Discussion
I'm not a biologist .. but some rule of thumb states that the chemical reaction speed roughly doubles with 10 K temperature increase. So at 40 C the oxidation might run at ~ 1/64 speed compared to at 100 C.
Also, preventing oxidation of fatty acids in the body appears to be one function of vitamin E: https://en.wikipedia.org/wiki/Vitamin_E#Functions
so instead of a minute in the frying pan it takes an hour, by which point it has yet to be absorbed in the gut, much less expelled
Sounds like you're assuming that one minute in the frying pan at 100 C or one hour in the body at 37 C already leads to a degree of oxidation that flips the balance from "contains PUFA and is overall beneficial to the body" to "contains some PUFA but also oxidized FA and is overall detrimental to the body".
Are you familiar with any facts to base this assumption on?
I don't think there's any point at which seed oils are beneficial to the body
The main fatty acid in most seed oils is linoleic acid, which has a clear disease pathway:
Linoleic acid metabolism is suppressed in diseased individuals:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9722286/
Linoleic acid levels are significantly associated with HNE (which linoleic acid produces when oxidized as in cooking) in both the general population and even more strongly in diseased individuals:
https://www.sciencedirect.com/science/article/pii/S2213231713000979
HNE is "the most toxic" aldehyde and involved in "important neurodegenerative diseases such as Alzheimer's disease, Parkinson's desease, multiple sclerosis and other diseases such as cancer, diabetes, inflammatory complications, atherosclerosis, osteoporosis, cataract and age-related macular degeneration." :
Also I'm looking for specific claims about the rate of oxidation and not seeing a paper on that topic, but I am seeing plenty that claim various connections between (dietary) linoleic acid and disease:
https://openheart.bmj.com/content/5/2/e000898
https://pubmed.ncbi.nlm.nih.gov/10671267/
Thanks for the links. I'll check them out.
This article seems to show that 225C for 25 minutes produces toxic levels of oxidation products in seed oils:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3118035/
so that rules out using them as frying oil (IMO) but of course the dose makes the poison
225 C is quite harsh.
Compare that to my usual procedure when making use of oils such as native lin seed oil or native canola oil:
- storing the oil with the glass bottle tightly sealed, in the fridge
- using the oil not for cooking but instead adding the oil to the finished meal just before eating
This way, the oil will be heated to maybe 60-70 °C at most and only for a few minutes while it's subjected to oxygen/air.