re: Cordain says canned fish is devoid of vitamins and toxic:

I personally have not come across this theory in any other info source.
I have been eating canned salmon and sardines for a while, and don't
find any side effects personally. The only bit of info I have come
across is related to eating large amounts of canned tuna which could
increase mercury levels if the fish was caught in a contaminated area.

Of course fresh is better than canned, but canned fish seems to be quite
tame. I can also only find canned fish in salt water or oil here.. maybe
in US they can it with other things such as nitrites etc. (as with
everything there).

re: never heat flax oil

Yes.. this one I have come across. Actually one source said to not heat
or fry ANY oil except maybe olive oil. Butter etc. are all no-no's when
cooked apparently and fats can turn rather toxic when heated. I don't
know the validity of this, but i eat fats and oils raw.
 
Apparently Flax oil is usually rancid even when it is in the store. For
this reason, I don't buy it / use it. I immagine heating it wouldn't do
any good for it.

reg.,
D.