I've been reading up on flax seeds and oil & from what I've seen, the only way to guarantee that you're not getting rancid flax oil -- seems to go rancid very quickly-- is to buy seeds and grind them up yourself, then eat immediately. One of the articles I read said Budwig says you need about 3 times as much ground seed per tsp of the oil, and that the seeds are fattening so that's one reason to use the oil. Apparently the seeds keep for a very long time unground, but once the hull is broken they go rancid right away. When I lived in the States, I could get flax oil at Whole Foods which was fresh- they kept it refrigerated-- but here in Spain I've yet to find a store that does that, so the one I'm taking is probably rancid :(. I need to buy a coffee grinder!
do a search in altavista for "flax oil" and you'll find lots of info on this.