I am extremely sensitive to caffeine, it makes me super jittery and I can feel my heart race.
For the last 4 years I've been adding 100mg of pure caffeine powder and 125mg L-theanine to a non-caffinated morning beverage. I even had someone secretly add or not add the L-theanine without telling me for a while, so it's as well controlled as an n=1 study can be.
The difference is pretty night-and-day for me, but obviously ymmv.
There's a lot of genetic difference in caffeine processing, and I happen to have almost every genetic variant associated with high sensitivity I could find studied.
For the last 4 years I've been adding 100mg of pure caffeine powder and 125mg L-theanine to a non-caffinated morning beverage. I even had someone secretly add or not add the L-theanine without telling me for a while, so it's as well controlled as an n=1 study can be.
The difference is pretty night-and-day for me, but obviously ymmv.
There's a lot of genetic difference in caffeine processing, and I happen to have almost every genetic variant associated with high sensitivity I could find studied.