[JohnsonB]

>This kind of thinking is simply not medically correct. The idea that eating a will lead to increase in b and then improve all these functions has no basis in evidence.

Well, sometimes it does, and I don't think the parent post made any sort of general point asserting that this was a universal principle. So if A is a necessary precursor to B and cannot be manufactured from more base components, we have a situation where low levels of B can impair some performance metric, and up to a point an increase in A will increase that metric. The body will maintain endogenous control of the various systems so long as it has the base inputs it requires. As an aside, even if A can be manufactured by cells e.g. cholesterol, there is the whole issue of whether the cells have enough energy/capacity to produce this compound in sufficient quantities at a given time along with all the other demands of them.

>Trust me. I'm a doctor :-)

You basically oversimplified the parent's post and presented it as a straw man, noting generically that we have low understanding of many processes in the human body without refuting his specific argument. That is not a well structured enough of an argument for you to be asking anyone to trust you just based on some imagined superiority in rank. (Hint: being an MD, even a PHD is not a refutation of an argument)