Earlier quoted context omitted.
Yep - raising my hand here. I've completely given up caffeine (including decaf, which isn't totally) because after I got a Fitbit, I realised that my morning coffee spiked my heart-rate to 120, and kept it thereabouts, slowly dropping to normal overnight, after which I'd start again. A genome sequence shows I'm a slow metaboliser (I expect more will show up with more research). I feel terrific now.
Slow metaboliser here. Also possibly more prone to caffeine addiction than most, according to said genome sequencing interpretation. I need to cap at 2 espressos per day before noon at most, or I start suffering side effects like poor sleep quality. People really need to reframe their coffee consumption from food to drug and understand their own usage and effects of said drug.
I strongly recommend Barleycup as an alternative morning cuppa.