Science is amazing, but it ignores reality all too often in trying to isolate variables. Common sense - as unscientific as it might seem - trumps isolated data. It might take science ten years to prove that flies eat poop. They'd have to set down tons of parameters, develop intrumentation to gather data, set up scenario after scenario to test, retest, peer review and verify the validity of each experiment. It might take weeks to define "flies", "eat" and "poop", and how they relate. And they'd uncover a lot of interesting - but largely useless - data along the way. But we both know flies eat poop. So when reports come out on both sides of the fence declaring flies don't eat poop, and flies do eat poop, you know where to stand.
Same for dietary science. We KNOW what humans eat. Plants, animals, each other, some dirt, some rotten fruit, bugs, etc. That's how we came about as a species, by eating everything in sight that didn't kill us off right away, and adapting to the rest, the mild toxins, and reproducing before dying.
Steak, eggs, potatoes - fruits, nuts, berries and forage. Coconut milk and potent herbs and spices. Tea instead of coffee now and teeny amounts of kelp daily. Let's see how this does! Not really had dairy much, and gut seems better for it.