The obvious statement is every single human is a little bit different in the way their body responds to what we eat and drink. My wife can get woozy and tipsy on one beer. I am a bit less sensitive to beer.
My MIL was no doubt was addicted to caffeine for a while. She was up to a full pot of coffee per day. She finally tried to quit and had horrible head aches. Now she acts like caffeine something to avoid. No coffee for her.
I do know if I am going to my doctors office for anything to avoid coffee before the visit. It does raise my blood pressure and they get all weird about that. With no coffee before the visit it is fine. I have a couple cups of coffee with breakfast and I am done for the day.