Sleep & Health

Why Does Coffee Make Me Sleepy?

Caffeine lovers have been perplexed by this riddle for years. When you wake up and grab that perfect cup of coffee, you find yourself fighting the want to sleep at your desk instead of feeling energized and ready to take on the day. What gives, coffee?

Why Does Coffee Make Me Sleepy?


  • What’s in Coffee to Keep You Awake?
  • Why Does Coffee Make You More Sleepy?

What’s in Coffee to Keep You Awake?

It's important to understand that caffeine, the magic ingredient in coffee, works by blocking adenosine receptors in the brain. Adenosine is a neurotransmitter that promotes sleep and relaxation, so when caffeine swoops in and blocks its receptors, we feel more alert and awake.

What’s in Coffee to Keep You Awake?

In an interesting version, you can imagine they are puzzle pieces. Adenosine and adenosine receptors fit together to make your brain feel sleepy, but caffeine can also bind to the adenosine receptors in place of adenosine. However, it does not induce sleepiness in the body like adenosine does, so after consuming coffee, we become more alert and stimulated.

Why Does Coffee Make You More Sleepy?

1. Gene

In a 2015 study, Kai Spiegelhalder and colleagues randomly divided 15 heterosexual couples into four groups and asked them to try four different sleeping arrangements: sharing a bed at the male partner’s house, sleeping alone at their own horse, sleeping alone at their partner’s house, and sharing a bed at the female partner’s house. For five days, they documented the participants’ sleep patterns and sleep quality diary. Upon comparing the data, the researchers discovered that although partners who slept together experienced higher-quality sleep than those who slept alone, where they slept didn’t have much impact on their sleep quality.

2. Stronger Caffeine Tolerance

Our brain produces more adenosine receptors in response to regular caffeine consumption, so creating a tolerance to the stimulant’s effect. This implies that to be as attentive as before, we will eventually require an increasing amount of caffeine. Therefore, those extra adenosine receptors go into overdrive when we don't drink as much coffee as normal or if we're just having a caffeine crash, leaving us feeling even more exhausted than we did before we drank that cup of coffee.

3. Wrong Timing

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Going back to what we were talking about earlier - the caffeine works basically by preventing adenosine and its receptors from “matching up.” However, if you happen to drink your coffee when adenosine and its receptors are already coupled, then caffeine just ends up being the awkward third wheel, unable to match this puzzle piece. So at this point, caffeine just has to take a back seat and watch adenosine make us sleepy.

4. Too Much Sugar in Coffee

Such as vanilla lattes, caramel macchiatos, and high trans-fat content in instant coffee can lead to a rapid spike in blood sugar levels. An early burst of energy or enthusiasm could cause a transient sensation of excitement. However, the body’s insulin response starts working swiftly to bring blood sugar levels down, resulting in a sharp decline that might bring on headaches, exhaustion, and dizziness. It's critical to be aware of the possible consequences of consuming too much sugar in coffee beverages.

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