If saturated fat is good,
and the industrial seed oils are bad due to their oxidation,
then why are Avocados good since they turn brown in the air very quickly???
From what I understand, the turning-brown is oxidation.
If that's true, then how come Avocados are considered good?
(My butter doesn't turn brown in the air.)
Thanks for any insights on this, Mike
The browning of avocados is not due to its fat oxidizing ... it's due to an enzyme called polyphenol oxidase being exposed to oxygen. This is the same mechanism that causes other fruits (like apples or bananas) to brown too.
Checkout this Oil Comparison Chart. Not paleo-centric, but it will give you a good idea of where oils lay on the axes of healthy/unhealthy and for eating/for cooking.
Avocados are high in MUFAs (70% of FAs), and about an equal split of SFAs and PUFAs. Industrial seed and vegetable oils do tend to have higher PUFAs, and therefore do tend to spoil more readily that those high in SFAs.
The browning you are seeing is likely not because of fat oxidation.
EDIT: I think Beth nailed it wrt why avocados brown.