This is actually a thing I wish existed, but I don't have time and energy to make it right now. I'd pay $25 a month or more.
Basically it's an application that lets you do self-experiments like this, properly blinded and with good statistics. A challenge-dechallenge-rechallenge study is one of the ones I like, but if you want to do one you essentially have to design the study anew each time, and it would be convenient to run multiple at once if that's possible.
I'm not interested in generalizing, I just want to know if (for example) taking Vitamin D every day at 1000 iu is enough, or whether I should be taking more or less. I can get labs done on this, of course, but again I'm more interested in subjective wellbeing than blood levels beyond avoiding deficiency or hypervitaminosis.
Maybe such an app exists and I simply don't know about it.
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