I recently discovered that my first grader has learned two things about caffeine: it’s part of coffee, and it’s yet another wonderful gift humans have received thanks to plants trying to kill bugs. There’s obviously more to the story, even beyond listing the number of trimethylxanthine-containing products people regularly consume. It blocks neurological activity, while stimulating others. It can affect your circulation. It makes Daddy functional, and yet… I’d rather the kids avoid it when possible. After all, they need their adenosine, right?
Caffeine has a few physiological effects on us, but the big one is that it blocks adenosine from doing its job. Adenosine is a naturally occurring, inhibitory neurotransmitter. As long as you’re awake, it builds up in your brain, slowing you down to once again go to sleep, even from the start of the day. To slow you down though, the adenosine needs to plug into certain receptors in your brain, which gives caffeine an opening to buy you some extra perky time, pausing the clock on the build-up to your next bedtime. Caffeine molecules can fit into the A1 receptor well enough to keep about half the adenosine from doing its job, and until they’re cleared the adenosine just sits there instead of signalling your brain to slow down. This pause can also lead to boosted levels of dopamine and even epinephrine in your body, giving you a higher sense of alertness on top of not getting sleepier. This extra stimulation is also where increased heart rates, cooler skin and jitters can set in.
When the caffeine clears
This is all temporary though. Once the caffeine has been cleared from the A1 receptors, usually in around 45 minutes, you still have your normal build-up of adenosine waiting around, and it basically tries to catch you up, leading to a surge of sleepiness. In the long term, repeated doses of caffeine blocking your adenosine supplies can lead to an odd adjustment, wherein your brain can become more sensitized to the adenosine it does regularly receive, leading to blood-pressure drops when it finally hits you (which is why Daddy sometimes complains about a headache in the afternoon!) Caffeine’s effect on your blood pressure is actually leveraged by some headache medicines for similar reason, as it keeps your blood vessels contracted, which keeps pain sensors in your head from getting smooshed.
Risk or reward?
So where does this leave the multitude of people on Earth who consume caffeine on a daily basis? Are we being reckless with our adenosine supplies? Are coffee drinkers pooping on an unnatural basis? It may not be too serious, assuming you’re not disrupting your sleep cycles too much, forcing yourself to wake up with a build-up of yesterday’s adenosine still in your brain. There is some evidence that long-term caffeine consumption makes more permanent changes, but they may actually carry some benefits, like lower rates of dementia. That said, I think I’d rather my kids skip the dopamine/epinepherine boost and make it to bed on time. I also can’t risk them finishing the coffee before I’ve had my second or third cup of the day.
Source: Caffeine Chemistry by Anne Marie Helmenstine, PhD, About Education