I came across this video with the clickbait title of “How Much Tea Can You Drink Before Your Bones Crumble [1]” and I got worried. I drink quite a bit of tea, and now I find out it can cause brittle bones? But having watched the video, the person in question was a lady who drank 150 cups of tea a day (or rather—every day she brewed a gallon of water with 150 tea bags and drank that) who ended up with skeletal fluorosis [2], caused by an excess of fluourine accumulating in the body.
It wasn't the fluourine in the water that caused the issue (and the video goes into the history of fluoridation—it does prevent tooth decay), but that and an excessive amount of flourine in tea caused the condition. It seems that tea is one of the few plants that will suck up flourine and concentrate it.
But I don't think I have too much to worry about as I don't drink anywhere near 150 cups of tea per day.
At least I hope …