Does Coffee Really Wake You Up?

We have all gone through those times where we were attending a lecture or a presentation, apparently present in the moment, but were actually spaced out. Staring at thin air, we were jolted back to the present when directly addressed and did not know what was going on. If, like me, you find such situations embarrassing, yet are often unable to get adequate hours of sleep at night, you will understand why I drink coffee every day.

Coffee does a wonderful job at waking one up, and there is an actual biological explanation for how this happens. But does coffee wake up everyone? Well, almost everyone. There are some people who develop tolerance for caffeine over time, and some whose body just responds to caffeine in a different way.

How Does It Work?

The way caffeine acts to make us alert and more awake is pretty interesting. Basically, in our brain, there is a molecule called adenosine which is the brain’s natural, sleep-inducing chemical. When your body gets energy by breaking down energy molecules called ATP, adenosine is released. The human brain has neurons that have receptors for adenosine.

When adenosine attaches to these receptors, a string of chemical reactions takes place that results in the slowing down of release of important signaling molecules in the brain. This effectively means that you get sleepy.

Caffeine molecules have the ability to slow down this process by blocking the adenosine receptors. Caffeine and adenosine have a sufficiently similar molecular structure that caffeine molecules can wedge into the adenosine receptors and block them. Caffeine molecules are sufficiently different from adenosine molecules that they do not activate the adenosine receptors.

When adenosine is unable to fit into adenosine receptors, the process of slowing down of brain neurons does not begin and you stay alert and awake for longer.

Apart from keeping you awake and alert, coffee can also boost your mood. Do you recall situations where you were really sleepy, tired or overworked? Chances are, you were also irritable and in a bad mood at those times. Maybe you thought it is the stress and overwork getting to you. Not quite so.

There is a chemical in our brain called dopamine. It makes us feel good, happy, and uplifts our mood. The dopamine receptors in the brain are interlinked with adenosine receptors. When adenosine occupies adenosine receptors, dopamine cannot get in, leaving you sleepy and irritable.

When caffeine molecules block the adenosine receptors, there is still place for dopamine molecules to enter and attach with the dopamine receptors, hence you feel alert and are in a good mood.

Decreased Effect Over Time

a woman drinking from a coffee cup

If you consume coffee regularly, you might have noticed that your caffeine intake has steadily increased with time. From needing one cup of coffee a day to stay alert, you might now need a cup of coffee every few hours. This is because the brain adapts to regular consumption of caffeine.

When the adenosine receptors in the brain are always blocked with caffeine molecules, the brain makes new adenosine receptors. That means that if your caffeine consumption stays constant, adenosine will still be able to act on neurons in the brain and slow them down, making you sleepy.

Thus, to feel the same level of alert/awake, you will need to constantly increase your caffeine intake, since the brain keeps on manufacturing new adenosine receptors.

One significant result of this is that the withdrawal symptoms get increasingly severe. When a person who drinks a lot of coffee every day, tries to quit caffeine, there are suddenly a lot of adenosine receptors in their brain to which adenosine can freely attach.

When adenosine attaches to more than a normal or healthy number of adenosine receptors, not only does the person feel sleep at all times, they can also get headaches, depressed moods, and feel general tiredness.

The good news is that within some days, the extra adenosine receptors disappear, and your body readjusts so that you can feel as alert as ever even without taking any caffeine.

Caffeine – a Double Edged Sword

Caffeine doesn’t just help you stay awake. Its effects on the dopamine and adenosine receptors can have long-terms benefits, such as reducing the risk of diseases like Alzheimer’s, Parkinson’s, and some types of cancer. Caffeine also speeds up the body’s fat-burning process. Sports organizations believe that caffeine gives unfair advantages to athletes, and because of this, in the past, Olympic athletes were required to stay below a certain level of blood-caffeine concentration.

However, caffeine has it disadvantages, too. It can increase the body’s heart rate and blood pressure. It can result in increased urination and/or diarrhea, and also contributes to insomnia and anxiety.


coffee beans spilling out of a coffee cup; a dark grey surface

There are some people, however, who seem to be unaffected by caffeine. Even when they start taking caffeine for the first time, their body is largely unaffected by it. In most cases, the person’s body metabolizes coffee very quickly because it is not sensitive to the key ingredient in coffee. This is largely determined by a person’s genetics.

When your genetic disposition gives you the ability to process caffeine fast, you cannot experience its long-term benefits. Apart from genes, caffeine sensitivity is also affected by your weight, whether you smoke or not, and the medications you take.

Some Interesting facts

  • Caffeine is the most common drug in the world, with about 2 billion cups of some caffeinated drink being consumed in the world every day.
  • The effects of caffeine start showing just 15 minutes after consuming a drink laced with caffeine. The caffeine hit can last up to several hours.
  • Scientists conducted experiments on regular users and non-users of coffee and found out that there is no difference between the performances of the two groups.


Non-coffee drinkers often ask those of us who consume coffee regularly the same question, “Why do you drink coffee every day?” They remain completely unaware of the blissful neural jolt we rely on to function in the mornings and gleefully lean on during the day.