When I was doing strict carnivore 3 years back, I could tell the difference in the quality of my sleep when I incorporated caffeine and when I didn’t.
Nowadays, I only have coffee after I’ve eaten breakfast. I take a few sips of straight black coffee then cut it with real milk or real cream. I can’t explain the biochemistry at play here, but the caffeine no longer has any noticeable impact on my sleep.
I believe it's called tolerance. Don't drink any caffeine for a month, then retest your theory. You may be surprised.
I appreciate the suggestion, but I do caffeine on-and-off for weeks or a month at a time (no particular “strategy” involved) and the difference is still negligible at best when consumed on a full stomach and cut with a carb and/or fat.
But that’s as far as my sleep goes. I can of course tell the difference in my short term morning/mid-day energy with or without caffeine
