As usual when you attempt to defend whatever ridiculous belief you've picked up for no reason, you don't actually make any sort of actual argument: You just continue to just state things like doing so in and of itself makes you correct.
Again, your big brilliant argument here was that because the BBB is primarily made of a thing, it must be possible for that thing to move through it. How does this take into account that cholesterol is transported through the blood on lipoproteins? What about the parts of the BBB that aren't cholesterol? Why would it matter even if the BBB was 100% cholesterol?
And no, it is not a relatively recent theory. We've known since the 60s and 70s it wasn't possible. Davson's work in the 60s showed that the BBB required that things passing through needed to be lipid-soluble. Oldendorf's work in the 70s effectively proved that the more lipid-soluble something is, the more easily it could enter the brain, and anything else required specific transport mechanisms to cross. We have never found any evidence of those existing for cholesterol, and the lipoproteins cholesterol is carried in are both water soluble and large. Couple that with isotope studies from the 40s showing evidence of de novo synthesis, and this has effectively been known for more than half a century now.
