I guess they'll never thoroughly map the complexity of factors concerning healthy/unhealthy food. What is good for a population with this genetic heritage kills people with that genetic heritage.
North-Karelia Project in eastern Finland was once the Mother Of All Diet Surveys, a huge international
effort to make the folks there (especially men) change their killer diet, and to find out what-causes-what etc.
It gave a clear results: Fatty diary products and fatty meat (=hard fats) simply kill.
Now, the inuits have never eaten anything green, only hard fat, but cardiovascular diseases were unknown to them before they got aquainted with "white mans food".
Whatever you eat you go wrong from some perspectives, and right from other perspectives.
I believe the key is physical exercise. As long as you give your body a hard time in a constructive way, it will turn
any food into something healthy.