Comment by Brian_K_White
11 hours ago
I think that was a core plot point of a series of books by Niven I think. Humans are on a planet that has almost no phosphorus or maybe potassium in it's biosphere. Humans have to take it artificially by sprinkling a special salt on every meal. But it's very limited and expensive and so a significant part of the population are mentally handicapped to lesser or greater degrees, generation after generaion.
Ah, Destiny's Road, and it was Potassium.
"...dooming humanity to a slow mental extinction."
Great.
There was also Black Destroyer by a.e. Van vogt, where the cat-like creature specifically ate phosphorus: https://scifi.stackexchange.com/questions/153274
Star Trek episode 2 the creature removes all your salt. There are a lot of examples of a creature extracting all of something like that but these are kind of a different idea.
The potassium one is particularly horrible to think about because it's insideous. The problem removes your very ability to respond to the problem. The entire race just gradually devolving back to stupid, especially if it was from the result of our own actions consuming it all for some industrial or consumer purpose. And before that happens, for untold generations there would be rich people who could afford their kids to grow up with enough and perpetuate the permanent ruling class, and a permanent poverty class that physically can not ever escape or compete regardless of their attitude or effort.