I wonder if, to whatever extent, there are some that don't feel as if they have any other option. With so many people lacking health insurance in the US, doctors fees being high, salaries being low, and then even if they do spend the money to see a doctor it's can sometimes feel like the doc comes in, barely listens (or just flat out doesn't believe what you tell him/her **), writes a prescription for god only knows what, and then runs out.
I guess I can just understand the frustration, and the feeling of "well who knows me better than me? I'll figure this out!"
And on top of that, I think there is also a trust issue going on. Take "my plate" for example. All those grains would make me sick, but it's supposed to be "healthy" for me. So I guess I also wonder how much self experimentation is born out of realizing that just one piece of mainstream medical advice is wrong and then having that trust broken.
Is it valid? I don't see how it's any less valid than anything else. When it comes down to it, you only have the one life to live. So either you can figure out how you, personally, can really enjoy your time here, or you can do things that don't work for you because someone says it should and spend your life (possibly) miserable.
** Just as an aside: I have a lower body temperature than most. I always have. I've had thyroid tests and they all came back fine. This is just the way I am. Over the years when I've told doctors this, they've rolled their eyes at me or told me I was full of ----. Seriously, of all the things I could possibly lie to a doctor about, why would I pick that?!