If Coffee Is A Stimulant, Why Does It Make Me Sleepy?

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.

Man with beard in glasses sleeps in office on the table over laptop with coffee in hand
  • 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.

Caffeine Tolerance

Like any other drug, it is possible to develop a mild tolerance to caffeine. Even as little as 100 mg of caffeine a day can lead to dependence. If you cut back on caffeine temporarily, it may give you more of a boost when reintroduced.

The Sugar Rush Effect

As a stimulant, caffeine temporarily increases your heart rate and blood pressure, which gives you that feeling of energy and alertness. Those effects can wear off within a couple of hours leading to a crash that leaves you feeling worse than when you started. This is similar to the crash that you might experience after eating a large piece of cake.

Coffee as a Diuretic

Coffee is a well-known diuretic and can cause a cycle of dehydration. As you lose water through urination, your blood thickens and slows down as it moves through your circulatory system. This means that less oxygen is delivered to your brain and vital organs, which makes you feel sluggish. This forces you to reach for more coffee to combat the sluggishness, and the cycle continues.

It is possible to limit the diuretic of caffeine by being consistent in your level of intake. Of course, you should also drink plenty of water to help replace the fluids that you lose.

Caffeine and Adenosine

Adenosine is a neurotransmitter that causes you to feel fatigued. Caffeine blocks the receptors in the brain that receive the adenosine, which is why you may temporarily feel more energetic. Even though the receptors are not active, the body still produces adenosine. Once the caffeine wears off, you experience the full effects of the built-up adenosine and start to feel sleepy.

Adrenal Overload

Caffeine stimulates the neurons of the brain. Excessive neuron activity prompts the body to produce more adrenalin, which temporarily increases your energy level. Once the adrenalin wears off, you experience a crash. When this cycle is repeated several times a day, the adrenal system is overloaded, and you can experience a chronic state of “caffeinism” that can leave you feeling tired, irritable, anxious, and depressed.


How to Limit the Effects of Coffee

If coffee makes you feel tired, there are steps that you can take to reduce its effects.

  • Avoid dehydration by drinking a glass of water for every cup of coffee.
  • Reduce coffee intake to no more than two to four cups a day.
  • Drink unsweetened coffee so that you do not add to the “sugar rush” effect.

Finally, if you are constantly feeling tired and sluggish regardless of your caffeine intake, you should consult your doctor since there may be an underlying medical condition causing your fatigue.

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