"In humans defined lithium deficiency diseases have not been characterized, but low lithium intakes from water supplies were associated with increased rates of suicides, homicides and the arrest rates for drug use and other crimes."
"The available experimental evidence now appears to be sufficient to accept lithium as essential; a provisional RDA for a 70 kg adult of 1,000 microg/day is suggested."
https://pubmed.ncbi.nlm.nih.gov/11838882/
1000 micrograms = 1 milligram
Edit: I'm retarded with grams.
I already said this but 1000 micrograms = 1 milligram
So when they say 1000 micrograms per day they are only saying 1 milligram per day
I think if you keep this in mind then the nutritional dose might be lower than the medical dose
Except it is more complicated than that because people usually take molecular compounds containing lithium plus something else & lithium usually has a very low atomic mass compared with the other elements in the molecular compound
