Many of us rely on a jolt of caffeine to help us wake up in the morning or to push through that afternoon energy slump. If it seems like the boost that you were expecting wears off too quickly or never comes at all, you are not alone. To answer the question “Why does coffee make me sleepy?”, it is important to examine the various ways in which caffeine affects the body.
Caffeine and Genetics
We all metabolize caffeine at different rates. This is due to variants in a specific gene called CYP1A2.
- If you are a slow caffeine metabolizer, you are not as likely to experience a quick rush of energy after drinking a cup of coffee. On the other hand, the caffeine does stay in the body longer, so if you do not stop drinking coffee early in the afternoon, you may have trouble getting to sleep.
- Fast metabolizers tend to feel caffeine as soon as they drink it. They typically need to consume steady amounts of caffeine throughout the day in order to maintain the effects. Most fast metabolizers are able to drink coffee later in the day without it affecting their sleep.