The science for fish oil capsules is all over the map. Some show they are helpful; some show no benefit. Like Christian, I eat fish periodically instead of capsules.
I just sear liver briefly on both sides (if you get a whole liver, attempt to cut as thin as you can – Not easy!), and that’s basically it. Though if you’re new to liver, liver and onions are good, and there are plenty of items with liver in them.
As for these people who eat X and that’s it, like Shawn Baker’s “I only eat steak”, I have a hard time with that. For one, I can’t imagine (and right now cannot afford) to eat only steak. For two, I can’t see how that’s healthy. There are tons of meats out there, just had leg of lamb last night that I grilled/smoked. Delicious. There’s shrimp, mussels, other seafood, etc. Why limit yourself to one food? (Except for those people who have to do so because of disease.)