Something I wonder about, I have a bottle of hemp seed oil that came in an
opaque container like the flaxseed ones do. The labels on both the flaxseed
and hemp oil containers say, 'do not cook over 350 F'.

So I cooked with it at 350 F once. Then another time I cooked it at 400 F
(I won't do that again). I didn't smell anything 'acetone' like that I was
aware of, so I don't think the oil denatured.

However I am reading Dr. Weill's book on optimum health right now and he
says he doesn't recommend heating flaxseed/hemp oil at all. Says to use it
for cold stuff only (i.e. salads). He says you can tell when the fat has
gone bad by the smell changing to something acetoney and bitter like
linseed oil.

The stuff is really expensive too, so upon reflection, it's probably best
not to use it for baking food in the oven, and only reserve it for salads
until such a time as the price goes down. The labels on the bottle DO say
however temperatures of 350 F and under are fine and that is probably where
Cordain figured it's ok to use the oil in cooking, maybe his bottle said
400.