Why do some people feel even sleepier after drinking coffee?
Caffeine doesn’t actually perk you up—it just “takes up a spot.”
There’s a substance in your brain called adenosine, whose job is to tell your body, “It’s time to sleep.” Caffeine molecules look a lot like adenosine, so they get to the adenosine receptors first and block the real adenosine from getting in. That keeps sleepiness at bay for a while. But caffeine only takes up the spot; it doesn’t do anything else. Adenosine keeps being produced and continues to build up. Caffeine has a half-life of about five hours, meaning half of it is metabolized every five hours. Once the liver has metabolized it, all that built-up adenosine rushes in at once, sending you into a “caffeine crash.”
Differences in the CYP1A2 gene—which produces an enzyme responsible for metabolism in the liver—also mean that some people metabolize caffeine especially quickly. Their coffee may be broken down before it even has a chance to kick in. So it’s not that you ordered the wrong drink; it’s your liver and adenosine teaming up to make you pay for it later.
Next time you’re struggling to stay awake, try taking a 20-minute nap before drinking coffee. It often works better than forcing down three cups.
Caffeine doesn’t actually perk you up—it just “takes up a spot.”
There’s a substance in your brain called adenosine, whose job is to tell your body, “It’s time to sleep.” Caffeine molecules look a lot like adenosine, so they get to the adenosine receptors first and block the real adenosine from getting in. That keeps sleepiness at bay for a while. But caffeine only takes up the spot; it doesn’t do anything else. Adenosine keeps being produced and continues to build up. Caffeine has a half-life of about five hours, meaning half of it is metabolized every five hours. Once the liver has metabolized it, all that built-up adenosine rushes in at once, sending you into a “caffeine crash.”
Differences in the CYP1A2 gene—which produces an enzyme responsible for metabolism in the liver—also mean that some people metabolize caffeine especially quickly. Their coffee may be broken down before it even has a chance to kick in. So it’s not that you ordered the wrong drink; it’s your liver and adenosine teaming up to make you pay for it later.
Next time you’re struggling to stay awake, try taking a 20-minute nap before drinking coffee. It often works better than forcing down three cups.