flax is a varnish, you can get a gallon for about $ 20 and wipe it on wood for a nice protective coating.
eating flax seeds also gives the fiber and other things present, and the oil isn't in pure form so probably OK.
Same with fish. Cod liver oil will do the same thing. In nature, oil only occurs to minor percentage of the foodstuff and the other attendant materials guard against premature oxidation.