I concur. In my opinion the "impossibility of improving IQ" in gwern's first sentence should be understood as "impossibility of improving IQ through supplementa

I concur. In my opinion the "impossibility of improving IQ" in gwern's first sentence should be understood as "impossibility of improving IQ through supplementation at the current level". I think the source of the problem is rather our very limited understanding of maintaining and improving the brain functions. As far as my limited knowledge goes, we still cannot reverse many dementia-inducing illnesses; once we see deeper into them, maybe better supplementation will appear. It's understandable that various "trivial" methods at increasing IQ fail. (Heck, we don't know much about benefit/hazard of many chemicals that enter our body; and even when we do -- smoking, obesity -- people tend to disregard the advice.)