I've been worried about grass fed beef, specifically our lack of it. It's difficult to get in Prague and expensive. Whereas the local butcher is just a couple of blocks down the street and they are pretty friendly. So I was happy to come across something that seemed to show my fears were unfounded, at least as far as ω−3 is concerned. Beef contains so little PUFA anyway that it doesn't matter all that much.
But being the curious type, I decided to do a little research of my own. Here's a table I lifted from a paper by Cordain, et al.
And here's a table I shamelessly scanned from my copy of Mary Enig's, Know Your Fats: The Complete Primer for Understanding the Nutrition of Fats, Oils and Cholesterol.
100 grams of beef steak has 9.3 grams of fat (according to Dr Enig). If it was pastured that would mean 10% of it would be PUFA and the n-6/n-3 ratio of 2.2 so 291 mg of n-3 and 638 mg of n-6 (according to Dr Cordain). This gives us 83 mg/oz omega-3 and 182 mg/oz of omega-6 (notice that Dr Enig's table lists beef steak as having only 5.7 mg/oz ω−3!). It's not lost on me the silliness of mixing metric and imperial units.
Grain fed beef has 7% PUFA with a 5.19 ratio which gives us 100 mg of n-3 and 550 mg of n-6. This gives us 28.5 mg/oz of omega-3 and 157 mg/oz of omega-6
So a half pound grass fed steak would give one 664 mg of n-3 and 1456 mg of n-6, while the same size grain fed steak would supply 228 mg of omega-3 and 1256 mg of n-6.
Of course 100 grams of Atlantic Salmon has 2.2 grams of n-3 (at least according to Dr Enig's book) and only half a gram of n-6, the ω−3 equivalent of 26 ounces of grass fed beef!
While grass fed beef can't hold a candle to fatty fish superstars like salmon and herring (at least in the ω−3 arena) I don't think that the difference between grass fed and grain fed beef can really be called negligible. Not to mention the fact that grass fed is healthier in other aspects and very likely more humane. Too bad I don't have much access to it. Now I can go back to feeling bad about eating grain fed beef.