This is a completely unproven and untested theory, which is why it's in a blog post and not a paper (and maybe there already is a paper).
- Assumption 1: Most health conditions, at least in the modern world, disappear on their own (e.g., colds and flu)
- Assumption 2: Most people don't like simply waiting for a health condition to resolve itself and try to do something to cure it.
Result: If you don't account for the fact that you would have gotten better without doing anything, almost anything you try will appear to improve your health (e.g., eating soup/lemons/capers, standing on your head, applying a warm compress to your back, etc).
I'm guilty of this myself. It's very tempting to think that some weird remedy "worked", but you have to ask yourself whether you would have felt better anyway.