Health and Coffee Pt. 6: Coffee and the Brain

By Julianne Bierwirth, RD


Coffee has a chemical complexity that, through the roasting process, creates a broad range of vibrant flavor characteristics. This same molecular diversity is also responsible for a variety of health effects in humans. Caffeine is certainly the most well-studied, but it is far from the only pharmacologically active molecule extracted during a brew. Some of these chemicals are elusive, and their effects poorly understood. Others, after decades of research, have concrete benefits and detriments firmly borne out by data.

In this 8-part blog series, we delve into the myriad truths, half-truths, and indeed, fallacies, related to the impact that coffee has on your health. Is it good for you? Is it bad for you? Is it going to make your teeth brown? Does coffee make you smarter? Read on to find out.


As the neurological effects of caffeine are so potent, those who integrate coffee into their daily lives are best served by understanding how their brain responds to different quantities and timing. Can you drink an afternoon coffee without compromising your sleep? How much is too much for you? What does a day with no coffee feel like?

Understanding the alertness caused by caffeine starts with understanding sleepiness. Sleep is a relatively mysterious topic, even to scientists. You can wake up rested and alert and yet be relatively certain that in sixteen hours you’re going to feel your eyelids drooping again. It certainly seems like there’s a mechanism working away to reconcile the hours you slept with the hours you’ve been awake. The modern theory of sleep surrounds just such a mechanism and a signaling molecule in the brain called adenosine.

As you go about your day adenosine builds up in a section of your brain responsible for what neurologists call “sleep pressure”. More adenosine accumulates over the day, decreasing the speed at which your brain can handle information until a critical level is reached. Melatonin, a sleep hormone, is then released so that you’ll rest and let your body do all of the things it does while sleeping - growing, repairing tissues, and storing memories. As you sleep that adenosine gets cleaned away so that you start fresh the next morning...or not, if you’re not sleeping well enough.


Caffeine and adenosine are very similar chemically- so much so that the body confuses the two. After a coffee the neurons where adenosine builds up get loaded with caffeine temporarily, dampening the signal to the brain. You’re tricked into feeling like you woke up a just an hour or two ago instead of eight or nine hours ago. But when the caffeine goes away the real amount of adenosine is detected and your body gets tired twice as fast.

So how long does the boost last? That depends partly on how much coffee you had. Your liver can process and eliminate half the caffeine in your body in 4-6 hours, meaning that if you had a cup of coffee 5 hours ago about half of that cup’s worth of caffeine is still circulated in your body. 10 hours from now a quarter will still be there, and so on. This is partly why scientists suggest you should abstain from caffeine after 2 PM if you work and sleep relatively normal hours.

What’s primarily important is not getting into a caffeine dependency cycle. If you drink caffeine too late in the day and it affects your sleep you’ll be likely to overuse caffeine the next day to make up for the deficit. The next night’s sleep is unlikely to be great either. It’s a cycle that is unlikely to stop until a long weekend or vacation resets the clock, but you never get back the hours you missed. Caffeine may alleviate the most noticeable effects of poor sleep but the health issues that come with it will create larger problems than a single drowsy day.

Another neurological symptoms frequently associated with coffee is headache. Adenosine reduces blood pressure by opening up blood vessels. When caffeine blocks adenosine the blood pressure goes up, which can alleviate headaches. Frequently headache medicines contain caffeine to boost the efficacy of drugs like acetaminophen. However when the coffee wears off, or if you are a regular drinker and go a day without you might experience the opposite: an unusually low blood pressure and with it withdrawal headaches. Caffeine itself does not induce headaches, only the lack of it will create problems.


On the extreme end of coffee consumption is caffeine intoxication. The symptoms include anxiety, headache, agitation, and overexcitement. As adenosine is suppressed by caffeine the brain speeds up and adrenaline gets released. Adrenaline is responsible for the shakes, excitement, fast speech, and heavy breathing associated with the jitters. You end up feeling like you’re fighting for you life during an everyday meeting or class. The strongest contender for a cure seems to be exercise, which may increase the liver’s processing speed, though the research surrounding this is sparing.

Caffeine is a drug, and like any drug it can be abused. They key is understanding your body’s response and planning your consumption of caffeine accordingly, or else that late night espresso could feel like it haunts you for days.


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