The nutrition point is so difficult to evaluate - a lot of personal variation, many anecdotes, few good scientific studies, a lot of subjectivity and misattribution, people getting fired up online and turning it into ideology... it's very difficult to figure out what's true and what actually works for you.
I think it is mostly a case of scientific belief in a trial by error process: if you believe in trying a bunch of different ideas, you are likely to eventually hit on solutions that help or hinder. You do need some minimum set of ability and brain power to do this effectively. However, even prophylactic or placebo effects can be minor wins (so long as you can manage to avoid dangerous things, like too much https://en.wikipedia.org/wiki/Radithor ).
