Flax seeds, 1 ounce (2.5 tablespoons) contains 6,388 mg omega-3 (11.8 g total fat, 1,655 mg omega-6, 8 g fiber)
Chia seeds, 1 ounce contains 4,915 mg omega-3 (8.6 g total fat, 1,620 mg omega-6, 11 g fiber)
Walnuts, 1 ounce contains 2,542 mg omega-3 (18.3 g total fat, 10,666 mg omega-6, 2 g fiber)
I threw walnuts in there as a reference because they’re often touted as being a good source of omega-3. Both chia and flax are higher in omega-3 than walnuts. Flax has the edge. Of course, these numbers are just ball park. You can’t measure a fatty acid down to the thousands of a gram in a natural food product. But it’s a good guide.
More telling here is that both chia and flax contain more omega-3 than omega-6, while walnuts have more omega-6 than omega-3. Walnuts have less fiber and more calories/ounce too. But, as we saw, it’s hard to determine the amount of fat (and, so, calories) absorbed from foods, especially when that food is a nut or seed in its natural form. (Can I use the word “natural” here?)
Really, they’re all good. I think a diet that includes nuts and seeds is better than a diet that doesn’t.