People drink coffee for its ability to increase alertness.
However, for some people, coffee makes them more tired.
This is likely due to caffeine blocking the receptors of a chemical found in human cells called adenosine.
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It may also be due to poor sleep habits or the development ofcaffeinetolerance.
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Reasons Coffee Makes Some People Sleepy
Coffeeis a popular morning beverage.
Around 85% of the U.S. population drinks at least one caffeinated beverage daily.
Below are the reasons why caffeine may make some people sleepy.
Disrupts Nighttime Sleep
Many people drink coffee to wake up and stay awake during the day.
Then, when they go to bed, they have difficulty falling asleep.
Adenosine Blocker
Adenosineis a crucial part of the sleep/wake cycle.
It increases the time that someone is awake and decreases the time that they are asleep.
The time it takes caffeine to be metabolized (processed and used) varies from person to person.
About 99% of caffeine is absorbed within 45 minutes of consumption.
Caffeine Tolerance
People who drink coffee or other caffeinated products regularly can develop a tolerance to caffeine.
This means that they become used to the effects ofcaffeineand may need more to achieve their desired effects.
Taking in morecaffeineto achieve the desired effects can negatively impact sleep.
Ultimately, this leads to tiredness despite drinking coffee.
The caffeine causes a rise in glucose levels, which will then fall back down.
When these glucose levels return to normal, a person may feel tired and have lower energy levels.
Conditions Associated With Fatigue
There are many causes of fatigue.
It can be a normal side effect of physical exertion or lack of sleep.
Other caffeinated drinkswith similarcaffeinecontentshould have the same effects as coffee.
An example isenergy drinksrange from 40 milligrams (mg) to 250 mg. Coffee can be a good way to increase morning alertness but cannot cover up long-term poorsleep habits.
But for others, coffee can make them feel more tired.
This may be due to how the caffeine in coffee blocks the chemical receptors for adenosine.
It may also be due to caffeine tolerance and poor nighttime sleep.
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