Coffee nap: The brain benefits of combining caffeine with sleep

Coffee is known to many as a beverage that promotes wakefulness, thanks to the caffeine in it. But did you know that drinking coffee before taking a power nap can do wonders for your brain?

What's in a cup of joe

Coffee is the most abundant source of caffeine in the human diet. Caffeine is a bitter-tasting chemical that's naturally found in more than 60 different plants, and it's what gives coffee its stimulant effects.

One cup of coffee contains 95 to 200 milligrams (mg) of caffeine, and it's enough to increase your alertness, improve your focus and make you feel energized. Caffeine reaches its peak levels in your blood one hour after drinking coffee, and its effects can last for four to six hours.

Aside from stimulating your nervous system to keep you awake and giving you a boost in energy, caffeine also acts as a diuretic, helping your body get rid of excess water and salt by making you urinate more. 

But because too much caffeine can raise your blood pressure and increase acidity in your stomach, it's not advisable to drink too much coffee. According to the Food and Drug Administration, healthy adults without any heart problems should limit their daily intake of caffeine to 400 mg, or about four or five cups.

The science behind a "coffee nap"

A daytime nap, or power nap, is a short sleep that cuts just before you enter deep sleep. It typically lasts about 10 to 30 minutes, although 20 minutes is the ideal duration.

Unlike a longer sleep, a power nap won't give you a drowsy feeling when you wake up because it ends before you complete a full sleep cycle. Taking a quick power nap in the middle of the day is useful if you've had a lousy night's sleep because it can leave you feeling refreshed and energized.

A power nap also has a positive effect on your brain, as it leads to improvements in mood, alertness, reaction time, short-term memory, focus and concentration.  

So why is drinking coffee – a notorious sleep inhibitor – before taking a power nap a good idea?

According to studies, the caffeine in coffee can keep you awake by inhibiting a brain chemical called adenosine, which promotes sleepiness. Because caffeine and adenosine are structurally similar, caffeine molecules can block the function of adenosine by binding to the same receptors in your brain.

Normally, adenosine slowly accumulates in your brain throughout the day and is cleared at night while you sleep. But research has found that when you're sleep-deprived, the adenosine levels in your basal forebrain, a brain region that's crucial for both sleep and wakefulness, continue to increase. This means that adenosine has complete control over its receptors.

In order for you to enjoy the full effects of caffeine, your brain must first free some of its receptors from adenosine. This is where a power nap comes in handy. A short nap can help reduce the adenosine buildup in your brain so that caffeine can compete for and bind to open receptors.

And since caffeine takes at least an hour to reach peak levels in your blood, you have more than enough time to take a power nap and let it do the trick. Together, a power nap and caffeine can give you a much-needed energy boost, increase your alertness and make you mentally sharper.  

Are coffee naps effective?

The mental benefits of a coffee nap are well-studied and backed by science. For instance, a study published in the journal Ergonomics reported that participants who were given caffeine and allowed to take a nap following a 24-hour period of sleep loss maintained a level of alertness close to their baseline levels and performed better on mental tests than participants who only took a quick nap.

For people who work morning shifts, after lunch is the ideal time to take a quick coffee nap. According to a study published in Neuropsychobiology, caffeine can counter the "post-lunch dip," or the drop in physical and mental performance that occurs naturally in the early afternoon. Participants who were given caffeine performed better than their non-caffeinated counterparts on the Bakan vigilance task, which measures alertness and sustained attention.

People who work night shifts can also benefit from taking a coffee nap. In a recent study, Australian researchers reported that people on a simulated night shift who consumed 200 mg of caffeine right before taking a 30-minute nap enjoyed improved vigilant attention and reduced fatigue after they woke up. This suggests that a coffee nap can boost sustained attention in drivers who work at night and help them stay awake and alert while on the road.

Taking coffee naps also provides benefits for highly trained athletes. According to a study published in Frontiers in Psychology, the combination of caffeine and a post-lunch nap enhanced the reaction time of athletes following partial sleep deprivation. A similar study published in the International Journal of Sports Physiology and Performance found that a coffee nap helped improve the performance of sleep-deprived judokas.

Tips for a good coffee nap

In order for your coffee nap to work, experts say that timing and sequence are key. Here are some tips on how to take an effective coffee nap:

• Take your lunch first - As shown by multiple studies, a coffee nap is most beneficial when taken after lunch.
• Get a cup of coffee or double shot of espresso - Since your goal is to consume 200 mg of caffeine, get yourself a 12-ounce cup of coffee or two shots of espresso.
• Drink your coffee quickly - Since you need to sleep before the caffeine takes effect, it's important to drink your coffee quickly instead of leisurely. You can opt for ice coffee if you can't consume hot drinks quickly.
• Set your alarm for 20 minutes and try to sleep - It's okay if you don't fall asleep immediately after drinking coffee. Just close your eyes and relax. Even a non-sleep dozing state is effective. Remember that your nap should not exceed 20 minutes to avoid feelings of sluggishness or grogginess when you wake up.