Caffeine can cause bladder and kidney problems. It’s irritating. Sometimes it causes kidney stones. I was pregnant when it became painful to drink it, though looking back I think it caused minor bladder issues for years. Maybe I’m sensitive to it. No maybe about it, actually. :-; I was just telling someone drinking decaf tea too many days in a row makes me feel shitty though it’s not painful, lack of energy for a couple days. I was verified on FPH on Voat, would verify again if Poal started doing that. So definitely not a fatty. I’m usually pretty healthy, and haven’t had that issue at all since quitting coffee. I may have been exaggerating about how bad it is, but it’s certainly not a harmless substance and IMO most are better off without the habit of drinking it daily.