I haven't seen anywhere mentioning any toxicity to the spice. Everywhere i looked no side effects. That costs too much money for me anyway, to eat a lot of it, and i guess for most people. A millionaire who values his brain too much, may try it. Someone like PG or Marc Andersen.

[edit]I would love to see PG coming back, programming a new Common Lisp by hand, and writing a 1000 page manual just by himself, if he gets a supercharged brain. GPT and Artificial intelligence will be left back in the dust.