It's harder than that. Our food supply has changed; sixty years ago when cows ate grasses, beef naturally had some omega-3s in it. Now that their diet is largely corn, beef brings virtually all omega-6s.

Ditto for "shelf-stable" foods. Omega-3 fatty acids go rancid at room temperature, so many packaged products have had the omega-3-based fats removed so they'll last longer on the shelves.

Source: my wife, who has a PhD in nutrition.

My understanding (from investigating this a couple years ago) is that grass-fed beef, while higher in O3's than corn-fed beef, is not a particularly significant source of dietary O3.

I think that is accurate. I only meant to use beef as an example of how our food supply has changed, not to suggest that beef is any sort of good source for omega 3s.

Check out http://www.ncbi.nlm.nih.gov/pubmed/16500874

Correct me if I'm wrong, but it's not just that grass-fed beef is higher in Omega 3, but lower in Omega 6. So it's not just about Omega 3 intake, but the ratio between the two.

I believe that is the main reason it is labelled as such and more expensive than regular grain fed beef. Same with free range/cage-free eggs.

Wild Salmon should be a good omega-3 source, while Norwegian grown salmon is probably not.

Here is a link to small study about this.

> The results show a little more of the healthy long-chain marine omega-3 fatty acid forms known as EPA and DHA in farmed salmon than in wild salmon.

> [..]

> “Indeed, there is a larger amount of omega-6 in farmed salmon. You get nine times as much as when you eat wild salmon,” says Research Fellow Ida-Johanne Jensen at the Norwegian College of Fishery Science.

http://sciencenordic.com/farmed-salmon-retains-good-fats

So it says that farmed salmon has slightly more O3 and 9x more O6. But how are the absolute ratios, is the salmon O6 content enough to matter if we want to balance out the presumably much larger O6 already in our bodies?

There's a certain optimal ratio between the various omegas. You could get too much or too little from any particular kind. It just happens that modern diets have too much omega-6 and not enough omega-3.