My former GP had me read the Omega Diet when I first started seeing him. The book that started the Omega 3 awareness. It talks of the vegetable oils. Very roughly, there are the oils of the common grains that are Omega 6 sources and oils from the dark green veggies and some others like flax seed. And olive oil which has neither but is in many other ways, simply excellent. That author postulated that the optimum blend of human health was 6 parts Omega 6 to one part of Omega 3.
The 6:1 ratio makes it sound like getting enough Omega 3 is a breeze. It isn't. Agriculture has effectively tailored our food to be entirely Omega 6. Putting cows, goats and pigs out to pasture in fields and woods with a lot of the dark stuff isn't efficient. They fatten up far faster eating pure grain. And over-eaten fields have don't have much in the way of dark greens. Things have gotten better. Here in Portland, the stores offer what I call "goat food". Kale, chard, spinach greens, mustard greens ... The veggies that used to be just weeds.
I take a fish oil capsule every night for its 1000mg of Omega 3. Or, it that isn't to be had, flax oil capsules. Use peanut oil only when I need an oil that can handle the hot wok. For everything else, I use olive oil. I do love and consume peanut butter. I have access to freshly made, 100% peanut every Saturday at the farmer's market. A farmer's grand mother makes it. So thick it doesn't spread until it's warm. (Kept refrigerated.) I do a small jar a week.
The pursuit of the Omega 3s seems to work for me. The pasty 20 years I have felt much better than I did the 15 years prior. I've never matched the feeling of my 20s when I was a bike racer, totally in form and ate well, no meat, milk and little white powders. (Salt - very low, sucrose - next to none, little white flour, none bleached ...) Now I have to live with the crash damage I compiled then and later. Blah, blah blah. Aging sucks. But my gut works very well. I feel fully alive. Life is good.