Drank Coffee and Fell Asleep: Scientists Explain the Paradox

Why doesn’t the morning drink energize everyone?

Caffeine is the most widely used psychoactive substance in the world: every day, people drink more than 2 billion cups of coffee, not counting cola, energy drinks, chocolate, and other products containing caffeine. Some people become more alert and concentrate better after coffee, while others experience almost no effect even after several drinks.

BBC reports on this, explaining why different people’s bodies react differently to caffeine.

How caffeine affects the body

Caffeine does not give the body energy in the literal sense. It blocks the action of adenosine—a substance that gradually builds up in the brain throughout the day and contributes to drowsiness. That is why a person may feel more alert after a cup of coffee, even though the fatigue itself does not disappear.

After coffee is consumed, caffeine quickly enters the bloodstream and reaches the brain. At the same time, the liver begins breaking it down, and the remnants of the substance are excreted in urine.

According to Dr. Marilyn Cornelis of Northwestern University, this process can last anywhere from 6 to 20 hours in different people. Therefore, a person may not feel much effect from the first cup, but several hours later a second dose of caffeine may already cause anxiety or inner tension.

Read more

News

Get a State Grant

Read Political Analysis

Why coffee affects everyone differently

One reason is the CYP1A2 gene, which is linked to the rate at which caffeine is broken down in the liver. In other words, the substance may be eliminated more quickly from one person’s body, while remaining longer in another’s.

A person’s ancestry may also affect the rate of metabolism. A study published this year found that Europeans and South Americans break down caffeine faster on average.

However, genetics is far from the only factor. Smoking, for example, can significantly speed up the breakdown of caffeine—by approximately 65%, according to the BBC. This may partly explain why smokers sometimes consume more coffee, and why their usual cup suddenly begins to have a much stronger effect after they quit smoking.

The opposite situation also occurs: some antibiotics, birth control pills, and other prescription medications can slow the breakdown of caffeine. In that case, it remains in the body longer, and its effects may last longer.

Coffee habits matter too

People who drink coffee regularly gradually become less sensitive to caffeine. The body adapts to the substance’s constant presence, so the same amount of the drink may produce a weaker effect over time.

This can be noticed after a break. If a person does not drink coffee for several weeks, the changes in the brain associated with adaptation to caffeine gradually disappear. As a result, the first cup after a long break may trigger a stronger reaction—from a feeling of excessive alertness to trembling and nervousness.

Pregnancy also affects the body’s reaction. Due to hormonal changes, the liver enzyme that breaks down caffeine works more slowly, so the substance may remain in the body longer.

When it is better not to drink coffee

Sleep specialists often advise avoiding caffeine for at least 6 hours before bedtime. At the same time, there is no universal rule for everyone, since the rate of metabolism and sensitivity to caffeine vary greatly.

Psychologist and sleep expert Lindsey Browning advises people who go to bed around 22:00 to consider giving up caffeine after 14:00. But she notes that this recommendation cannot be the same for every person.

Caffeine may not only delay falling asleep but also worsen sleep quality. Therefore, the absence of an obvious effect—for example, when a person quickly falls asleep after drinking coffee in the evening—does not necessarily mean that the drink has no effect on the body at all.

Read more

Support a Human Rights Organization

Subscribe to the News

Explore Historical Archives

At the same time, for most adults, moderation remains the main recommendation. The British health system advises pregnant women to consume no more than 200 mg of caffeine per day—roughly the amount contained in two cups of filtered coffee.

Large doses of caffeine can cause headaches, trembling, a rapid heartbeat, anxiety, and sleep problems. Overdoses are rare, and the most severe cases are usually associated not with ordinary coffee but with concentrated caffeine-containing products.

Coffee lovers have another piece of news as well: years of research have linked moderate coffee consumption with a lower risk of some serious diseases and a slightly longer life expectancy. At the same time, such studies show an association rather than proving that coffee is the sole cause of these outcomes.