Skeletal fluorosis is a disease of the bones that occurs from excessive intake of fluoride. Fluoride is found in drinking water and in brewed tea. Skeletal fluorosis causes pain in the bones and brittleness in the teeth.
The New England Journal of Medicine found this condition was caused by excessive intake of fluoride (>20 mg fluoride per day from 100-150 tea bags per day) over an extended period of time. When the tea drinking was topped, symptoms improved.