A lot changed in the 70s and a lot of problems, coincidentally, came with them. Just completely swapping "vegetable" oils with something like lard/butter is kinda crazy the amount of change and improvement most people I've commit to it have experienced. There are plenty of other things as well, but that is definitely a big one in my experience.

This was one of the very first things we did when we started our journey about 15 years ago now.