I dispute the 15-20%. It’s closer to 5% and only that high in women (lower in men, an enzymatic thing).
Thus this list I found in a quick internet search is total bullshit:
Top 10 Foods Highest in Omega 3 Fatty Acids
1.Flax Seeds.
2. Chia Seeds.
3. Fish (Salmon)
4. Walnuts.
5. Firm Tofu.
6. Shellfish (Oysters)
7. Canola Oil.
8. Navy Beans.
9. Brussels Sprouts.
10. Avocados.
https://www.myfooddata.com/articles/high-omega-3-foods.php
This list is appropriate (minus the non-fish items):
12 Foods That Are Very High in Omega-3
1. Mackerel ( 4,580 mg per serving)
2. Salmon ( 2,150 mg per serving)
3. Cod liver oil ( 2,438 mg per serving)
4. Herring ( 2,150 mg per serving)
5. Oysters (329 mg per serving)
https://www.healthline.com/nutrition/12-omega-3-rich-foods
I left the sardines & anchovies off the list because they’re typically canned, and the canning process destroys the fragile O-3. If you can find them fresh and tolerate them, go for it.
Fish must be cooked low & slow (think poached) to retain health benefit.
Otherwise all you’re eating is fish flavored chicken.
Cod liver oil must be fermented, otherwise the likelihood is that it’s been processed and had negligible O-3, if any at all.
Reminder: All supplements are unregulated. Most fish oil capsules are a total rip-off and likely unhealthy IMHO.
I prefer river trout because it’s low in mercury and not exposed to Fukushima contamination.
For supplements, I use ConsumerLab and Consumer Report for their independent tests of the oil and its rancidity.
Strangely, the best for the price is Walmart Spring Valley 1,000 and 2,000 mg Omega-3 fish capsules. Just under 9 cents a capsule in the 180 count bottle.
The problem is that no one really knows what FCLO is, or should be. The product promoted by the Weston Price Foundation was shown to be not cod-liver (it was pollock) and demonstrably putrid.
Supposedly, the Romans used FCLO, but there does not appear to be any agreement as to how this was made.
Holy Mackerel!