Coffee. What’s the deal with this beloved beverage and how can it do what it does.

Written by : Annamaria Rodrigues

You probably have a friend who’s obsessed with coffee; always got a cup in their hand and is unable to function in its absence (or maybe you’re that friend). But what is it about coffee that makes you feel so alive?

The major molecule which is responsible for coffee’s addictive potential is caffeine. As a matter of fact, caffeine is the world’s most popular drug and is consumed widely in the form of tea, chocolate, soft drinks, and so many other sources (and also coffee… of course).

Caffeine molecules have a really similar structure to another molecule found in your body called adenosine.

Adenosine is a by-product of the breakdown of ATP, your body’s energy currency. As your body uses energy for various tasks throughout the day, adenosine molecules accumulate in your blood. These adenosine molecules bind with adenosine receptors found in your brain and tell your body that it’s nap time. The more adenosine binding to their receptors, the more drowsy you’ll feel.

Since caffeine has a similar structure to that of adenosine, the two molecules compete with each other to bind with the adenosine receptors in your brain. Increased caffeine molecules in the brain decrease the chance for adenosine molecules to bind with the receptors. The technical term for this is competitive inhibition: caffeine is a competitor to adenosine for a binding spot, so, it inhibits adenosine from doing its job effectively. This means there are fewer signals telling your body that it’s tired. As a result, you feel less lethargic and more energized.

Adenosine receptors are also found in your heart and kidneys. When activated by adenosine, they slow down your heart rate and decrease blood filtration in the kidneys to reduce ATP consumption by your body. But in the presence of caffeine, these activities are inhibited leading to increased heart rate and urine production.

Over time, your brain adapts to your coffee intake and synthesizes additional adenosine receptors to compensate for those clogged by caffeine. More caffeine is needed to block the new receptors and so, you may find yourself reaching for another cup of coffee more frequently. The newly synthesized adenosine receptors also explain the “withdrawal symptoms” faced by coffee-drinkers who go cold turkey. In the absence of caffeine, adenosine molecules bind to all the adenosine receptors present and increase feelings of drowsiness, and may also cause headaches.

This can be prevented by gradually slowing down your coffee intake instead of cutting yourself off abruptly. As your coffee consumption decreases, the number of adenosine receptors slowly returns to normal.

Caffeine is also known to uplift your mood and induce positive feelings. It does this by increasing the activity of dopamine, a molecule that makes you happy! There are some paired receptors in your brain where binding sites for adenosine and dopamine co-exist. But when adenosine binds to its spot in these paired receptors, it doesn’t allow dopamine to fit snugly into its site. Less dopamine binding, less happy feeling. But when caffeine binds to adenosine’s site on these paired receptors, dopamine can comfortably bind with its site and its effect is experienced. To quote the internet: More espresso, less depresso!