Is Caffeine Bad For Sleep? Why?

Is Caffeine Bad For Sleep?

Caffeine is absorbed within minutes, so reaching for coffee or an energy drink when you need to stay awake does the trick. But why is it so effective?

Caffeine is bad for sleep (and great for staying awake) because it binds with sleep-promoting adenosine receptors in the brain; fooling the brain into thinking rest is a long way off.

Adenosine is an inhibitory neurotransmitter that promotes sleep and suppresses arousal. It builds during the day, which is why you feel tired at night.

Caffeine has a similar molecular structure to adenosine, binding perfectly with adenosine receptors. You can think of this process as caffeine stealing adenosine’s parking space, only giving it back when it has finished shopping.

When you consume caffeine, you are filling in the space usually taken by adenosine which causes sleepiness with a stimulant.

The stimulative effects of caffeine also increase energy by boosting neurotransmitters, namely dopamine, the reward hormone that plays a significant role in motivation, mood, attention, and memory.

Caffeine and adenosine

The body uses adenosine to promote and maintain sleep and regulate arousal and excitability. Heightened levels of adenosine increase sleepiness, and levels increase during the day, making you sleepy.

Caffeine is an adenosine receptor antagonist that binds to receptors, stealing adenosine’s parking space. It stimulates you, making you feel alert, although the effects only last around an hour and can have a downer.

Sleep and Caffeine. — Pictured: A worker surrounded by empty coffee cups, asleep.

Because it is a stimulant, caffeine has the opposite effect, increasing alertness and excitability. By binding to adenosine receptors, caffeine inhibits sleepiness, keeping you awake even at ungodly hours.

Disrupted body clock

Caffeine is excellent for keeping you awake and extending waking hours, but it doesn’t take many nights of irregular sleep to knock your body clock out of whack.

Two to three nights of irregular sleep is all it takes to shift your body clock forwards a few hours. You may have difficulty falling asleep at your regular time because your body is not ready for sleep due to low adenosine levels.

We also know that caffeine interrupts the secretion of the sleep hormone melatonin, resulting in increased wakefulness.

These things disrupt your body clock, so consuming caffeine in the right quantities and at the correct times is essential.

Recommend cut-off times for caffeine

Experts recommend consuming caffeine no closer than six hours before bedtime, so 15:00 if you go to bed at 21:00.

This study into the effects of caffeine taken 0, 3, and 6 hours before bed found that caffeine taken up to six hours before bedtime has disruptive sleep effects.

Recommended daily caffeine intake

Depending on who you ask, 200 to 300mg of caffeine daily is generally considered healthy. The NHS recommends pregnant women consume no more than 200mg of caffeine daily due to the risk of underweight birth.

200mg is equivalent to two cups of instant coffee or five cans of cola. One can of Red Bull contains around 80mg of caffeine.

Watch out for hidden caffeine in food and drink

We all know that coffee, energy drinks, and cola contain caffeine, but did you know there’s caffeine in many non-cola sodas, chocolate, and health foods?

Chocolate contains lots of caffeine because it is found naturally in cocoa beans. 100g of 70% dark chocolate has a whopping 80mg of caffeine!

Protein bars and shakes are also often caffeinated, with a Mars protein bar containing 3mg of caffeine per 100 grams.

Decaffeinated coffee and tea still contain caffeine, albeit in the paltry amount of around 2mg per cup, so you’d have to drink lots to stay awake.

It would be best if you were most wary of chocolate desserts, chocolate cereals, ice cream, and protein snacks because these soon add up to lots of caffeine.