Well.... alot of things are largely anecdotal. I believe I heard Robb state once that the existence of the universe is largely anecdotal. But in any case, research studies have also proven alot of BS. I've seen studies where they insisted that high carb diets were better. I've seen studies that found that eating meat was bad for you. At every family gathering, my vegan cousin brings me another study "proving" that eating meat is bad.
All I can say is what works for me. Eating more omega-3s makes me feel better whether it's from drinking fish oil or eating free range grass fed beef. I noticed the difference when I switched from conventional foods to foods with more omega-3s, and when I go on vacation and don't have those foods available, I can feel the difference then too.
If you want a case study, my 66 year old uncle lives on a farm in Kentucky and all the animals are free to roam, so the eggs, dairy, beef, chickens, goats, etc are all free range and grass fed. At 66, he can still do 30 dead hang pullups. I'd like to think that his diet plays some role in his health. You don't see too many men in their 60s who can do 10 pullups let alone 30.