Evolutionary speaking, we are built to forage and hunt food. This meant that our diet was historically hugely varied - far more than it is today.

Personally, I believe that our best bet is to seek to eat as varied a diet as possible - and ideally not eating too much in terms of portions (ideally with a bit of fasting here and there).

I suspect that our main problem today in the Western world is over-nutrition!

But having said all that, I'm no medic or doctor so take everything i say with a pinch of salt (just not too much salt cos that would be bad for you ;) )