So, coffee napping is a thing.
Apparently, you get more benefit from drinking coffee immediately before taking a 20 minute nap than you get from only drinking coffee or only taking a 20 minute nap.
The way it works is interesting. The reason you get tired is because as the day goes on, your brain produces adenosine, a chemical that binds to specific receptors in the brain and tells the nervous system to slow down. This makes you less alert and sometimes quite sleepy, especially after using your brain a lot. Taking a short power nap can lower the amount of adenosine, making you more alert.
Adenosine is a nervous system suppressor, and when you ingest caffeine, it inhibits adenosine and stimulates the nervous system in a variety of ways.
It pretty much is that simple. But more specifically, at the molecular level, caffeine resembles adenosine, and binds to adenosine receptors in the brain. This means adenosine cannot bind at the receptors blocked by caffeine and so the nervous system suppressing effects of adenosine are blocked.
So both caffeine and power napping are ways to stimulate your nervous system and be less tired and more alert.
A coffee nap combines these two things together. When you ingest the caffeine, it takes 20-30 minutes for it to be absorbed in your small intestine. So if you lie down for a power nap immediately after drinking coffee, say, your adenosine levels begin to drop, and when you wake up, the caffeine is starting to enter your brain. Due to the nap, the caffeine has less adenosine to compete with for brain receptors and thus it has a greater stimulant affect by blocking adenosine from binding those receptors as adenosine levels begin to rise again.
They did studies and it appears to be true.
However, I have a question. After a good night of sleep, adenosine levels in the brain should be at an all-time low. So why am I so groggy and sluggish in the morning? Coffee in the morning does seem to have more potent awakening effects than coffee later in the day, presumably because it has very little adenosine to compete with when I wake up. But I usually wake up groggier than when I fell asleep, and that’s a quandary.
Here’s a list of the amount of caffeine in various ingestible things.