Beep beep beep. It’s 6 am, you’ve hit the snooze button three times but that menacing alarm clock is still blaring its wake up call. You can’t remember your own name much less find the strength to pull yourself from your cozy nest. Then it hits you – the intoxicating aroma of a freshly brewed pot of coffee wafts by your nose and you suddenly have the motivation to move.
How is it that even just the smell of coffee can make you feel perkier? If you can’t start your day without a moderate dose of caffeine, you’re not alone. Over 150 million Americans partake in a morning cup of joe, and many continue drinking all day long.
Plenty of studies boast of coffee’s many health benefits and a few point to its downsides too, but what’s the deal when it comes to sleep? Can caffeine and sleep co-exist? Let’s find out!
How Much Caffeine Does the Average Person Consume?
Legend has it that a goat herder by the name of Kaldi was the first to discover coffee thousands of years ago. The story goes that Kaldi noticed his goats eating a mysterious bean and hours later they had so much energy they couldn’t sleep. The cultivation and trade of this bean began in the 15th century in Arabia, eventually spreading to neighboring countries and around the world.
Coffee arrived in America by the mid-1600s, but it wasn’t until the Boston Tea Party revolt in 1773 that it became the preferred beverage choice by Americans (and remains so to this day). Nearly every coffee lover has spent a small fortune on a delicious Pumpkin Spice or Salted Caramel latte at America’s favorite coffee shop. In fact, Starbucks was responsible for a 700% increase in coffee consumption between 1995-2000.
90% of North American adults and 85% of Americans over the age of two consume at least one caffeinated beverage on a daily basis. In fact, caffeine is the most commonly used psychoactive drug in the world.
I know, you’re shocked! So was I. As a parent of three kids (one who is currently two), I was floored to read that I may be unknowingly drugging my kids with a psychoactive substance every day.The average person consumes around 200 mg of caffeine per day with the highest consumers taking in closer to 380 mg.  While coffee is the number one caffeinated beverage choice, those under 18 tend to prefer soft drinks and tea.
You probably already knew that coffee contains caffeine, but there are plenty of other sneaky sources of caffeine that you may not be aware of. Caffeine can also be found in other flavored drinks, chocolate, breakfast cereals, ice cream, hot cocoa, herbal teas, certain medications, energy drinks, and many food additives.
I’ve definitely made the mistake of letting my kids have chocolate too close to bedtime only to face the wrath of the three-foot-tall zombie apocalypse when my wired-tired children won’t go to sleep that night. If you’ve ever laid there tossing and turning after a pint of rocky road, caffeine could be the culprit.
Let’s take a look at the amount of caffeine found in different foods, keeping in mind that physicians recommend adults limit their intake to 400 mg a day and the American Academy of Pediatrics recommends that children under 12 avoid caffeine entirely.
How Much Caffeine Is in Your Food?
How Does Caffeine Work?
Have you ever wondered what caffeine is and how it works? This chemical compound is naturally found in over 60 different plants where it acts as an organic pesticide. In humans, it stimulates the central nervous system (CNS), creating an energizing effect that wards off fatigue and promotes mental alertness.
To fully understand how caffeine works, we have to take a step back and look at why you feel sleepy to begin with. There are many different systems in the body that regulate sleep. One of these systems involves chemical messengers known as neurotransmitters.
Adenosine is a type of neurotransmitter that makes you feel sleepy. When you wake up in the morning, levels of adenosine are at their lowest. As you go about your day, adenosine levels gradually build making you feel more and more tired.
The longer you’re awake, the more adenosine your brain generates until you can’t resist sleep any longer. Scientists have discovered that adenosine may be one of the chemicals responsible for “sleep debt.” Kind of like a bank account, if you don’t get enough sleep to pay off your adenosine balance, that amount carries over to the next day.
If you were to get only 5 of your body’s required 7-8 hours of sleep, you would wake up tired because you still have leftover adenosine floating around in your brain.
Now, let’s look at how a simple cup of coffee plays into this equation. It is very similar to adenosine at a molecular level, so it can bind to the same receptor sites in the brain. Even though adenosine is still building after too little sleep, caffeine blocks your brain from its “I’m tired” signals and sends the opposite message – “I’m awake and full of energy.”
If only science teachers had taught cool lessons like that in school! But before you go rushing out to share your newfound knowledge with all of your friends, there’s another important point you need to know…caffeine eventually wears off! And when it does, all of that building adenosine comes rushing back like a floodgate being opened, binding with your sleep receptors and causing that awful crash you experience mid-afternoon.
Another downside to having caffeine bind to adenosine receptors is that it triggers the body’s fight or flight response. The pituitary is a hormone-secreting gland at the base of the brain that is constantly sensing brain activity and is responsible for stimulating the sympathetic nervous system to act in a state of emergency.
While the cost of a Starbucks latte should cause some alarm, drinking your morning coffee shouldn’t feel like a life or death situation. Unfortunately, your brain can’t tell the difference. When you drink coffee, the “fight or flight” branch of the nervous system that deals with stressful situations is activated, and your body responds accordingly – dilated pupils, increased heart rate, sweaty palms, racing thoughts, and increased blood sugar.
Staying in a prolonged state of emergency isn’t healthy for your body and can lead to things like adrenal fatigue and all kinds of other issues. Research has found that caffeine can increase cortisol (our stress hormone) in the body, but other studies have found this doesn’t have any long-term effects on our health. The jury is still out on the matter, but most health experts agree that old adage of “everything in moderation” likely applies here too.
Check out this neat TedED video that explains more about how caffeine keeps you awake!
How Long Does It Stay in Your Body?
Caffeine can pass through epithelial tissue, which means that even from your first sip, the body is absorbing it through the mouth, throat, esophagus, and stomach. Within 45 minutes, 95% of it has been absorbed in most individuals and after 4-6 hours, half of it has been cleared from your system. 
Researchers have discovered that many factors influence how each individual reacts to caffeine. Everything from age to gender, hormones, activity level, ingestion with food, medications, and even genetics may play a role. 
Another difference may relate to one of caffeine’s metabolites – paraxanthine. According to research,“The plasma concentration of caffeine decreases more rapidly than that of paraxanthine, its main metabolite. The concentrations of paraxanthine become even higher than those of caffeine at about 8–10 hours after caffeine ingestion and this occurs in all species…This is critical given that paraxanthine is as potent as caffeine for the blockade of adenosine receptors.” 
What this means is that even though the stimulant is mostly inactive after 8 hours, paraxanthine could still be blocking adenosine up to 10 hours later. If you drink a cup of coffee around noon, paraxanthine may the reason you can’t fall asleep at 10 pm.
Scientists have identified 3 different levels of caffeine sensitivity based on your unique genetic makeup. We’ve all met those people who claim they can drink a shot of espresso and still fall asleep an hour later. These types of individuals make up 10% of the population who have limited sensitivity to it.
Other people (myself included) are overly sensitive to caffeine, reacting to even small amounts with shakiness, rapid heart rate, and insomnia. For us, drinking a single cup of coffee could keep us awake for hours, possibly even preventing us from falling asleep that night. The third group of individuals are those who metabolize it “normally”.
Science has been able to explain why these different sensitivities exist. Some people make less of the CYP1A2 enzyme that the body uses to break down caffeine. Others have a genetic difference in the sensitivity of their adenosine receptors to the caffeine molecule. 
A really cool study performed at Harvard University looked at 120,000 people and found 6 genetic variations in how people metabolize and become addicted to caffeine. Two genes were responsible for how caffeine is metabolized, two were associated with how we feel rewarded from it, and two genes were discovered that regulate fat and sugar in the bloodstream in response to it.
How Does Caffeine Affect Natural Sleep Cycles?
Have you ever wondered why sometimes you wake up and can remember your dreams and other times you swear you didn’t dream at all? Being able to recall your dreams typically relates to which sleep cycle you were in when you woke up. When humans sleep, we go through four different stages of sleep – rapid eye movement (REM) sleep, and three progressively deeper stages of non-rapid eye movement (NREM) sleep.
Caffeine doesn’t appear to have a large effect on REM sleep, which is the period where dreaming occurs. It does have an impact on NREM sleep, prolonging the time it takes to fall asleep, shortening total sleep time, worsening sleep quality, reducing deep sleep time, and resulting in more frequent awakenings. 
Read more about REM and NREM sleep stages here.
The research on coffee’s effect on sleep is all over the map. Some studies say that it has no effect on sleep whatsoever, and other studies have linked it to conditions like insomnia and harmful changes in the sleep-wake cycle.
A 2016 systematic review looked at 58 studies that have been done on caffeine’s effect on sleep. They discovered that people respond differently to it based on age, weight, individual levels of sensitivity, genetics, habits of intake, and time of consumption. Just like the differences in its metabolism, every person is unique in the way their body responds when it comes to the effect on sleep.
We do know that in certain people, caffeine and its metabolites have the ability to prevent the brain from going into a deep sleep, similar to the effects of alcohol on sleep. This means that while some people may be able to sleep after drinking coffee, they aren’t getting the deep, restorative sleep they need.
The researchers who performed the study mentioned above also concluded that caffeine may cause daytime drowsiness thanks to its impact on sleep cycles. This creates a vicious cycle because sleepiness during the day is often the reason many people turn to coffee in the first place. If you’ve ever felt “addicted” to coffee, this could be why!
Is There a Healthy Amount of Caffeine?
Does all this mean you should give up your daily java habit and take up juicing greens? Well, it’s not a bad idea, but don’t go joining coffee drinkers anonymous just yet. There are some health benefits to drinking coffee that you may want to hear about first!
Here’s a summary of some of the latest research on the health benefits of coffee:
Antioxidants: It has more antioxidants than green tea or chocolate, fighting free radical damage that underlies many diseases including cancer. 
Heart Health: Research combining data from 1,279,804 people discovered a 20% reduction in the risk of Cardiovascular disease in people who drank 3-5 cups of coffee a day. 
Prevent Type 2 Diabetes: Researchers at Harvard found that for every cup of coffee consumed, the risk of type 2 diabetes drops by 9%. 
Reduce Cancer Risk: Moderate coffee intake has been linked to a reduced risk of liver, endometrial, breast, and possibly colon cancers. 
Prevent Parkinson’s Disease: A study found that caffeine intake may lower the risk of Parkinson’s even in individuals who are genetically predisposed to it. 
Reduce Alzheimer’s Disease: In the Cardiovascular Risk Factors, Aging and Dementia Study, drinking 3-5 cups of coffee in midlife was associated with a reduced risk of dementia and Alzheimer’s Disease by nearly 65% later in life. 
Promote Weight Loss: A German study found that coffee drinkers were more likely to maintain weight loss than those who don’t drink it. 
This is just a small sample of the health benefits of drinking coffee. Plenty of other research has discovered benefits like lowered inflammation, blood pressure reduction, better athletic performance, improved focus and attention, reduced driver error, and more!
With a lot of the research studies that have been done on coffee, the benefits are dose-dependent. In other words, moderate coffee consumption appears to be beneficial (i.e. 3-4 cups) but excessive consumption does not. More than 4 cups can have the opposite effect, increasing the risk of heart disease and possibly even increasing the risk of death. 
Keep in mind that 3-4 cups of coffee means 3-4 eight-ounce (250mL) cups – not mugs, thermoses, and especially not Starbucks beverages. A Starbucks Grande holds 16 ounces and 310 mg of caffeine.
According to Mayo, most adults can handle up to 400 mg of caffeine per day, but as we saw earlier, every individual is unique. If you notice yourself feeling jittery and anxious after a single cup of coffee, you may be one of the “sensitive” types and may process it more slowly. Even if you are one of those types that can practically drink coffee in your sleep, it’s still wise to limit yourself to 400 mg per day based on health recommendations.
When’s the Best Time to Drink Coffee?
If you’re anything like me, you have your coffee set on auto-brew so you can wake up to that delicious smell. Unfortunately, drinking coffee first thing in the morning isn’t the best practice, because our bodies are still in a natural awakening state. Research has discovered that there is an optimal time to drink caffeinated beverages, and that time depends on something called your “chronotype.”
Your chronotype is when your body prefers to sleep and be awake based on your individual circadian rhythm, or 24-hour cycle. Inside the brain is something called the suprachiasmatic nucleus (SCN) and it helps to regulate your cortisol levels based on your circadian rhythm. Cortisol is a hormone that is commonly known as “the stress hormone.”
Cortisol levels naturally rise and fall throughout the day but can also become chronically elevated when you’re under stress. Elevated cortisol makes you feel alert and low cortisol makes you feel sluggish and tired.
If your chronotype is an early bird, you likely wake up as early as 5 am, energetic and ready to start your day. If your chronotype is a night owl, you likely struggle to pull yourself from bed anytime before noon. Circadian rhythms can differ between these two chronotypes by up to 12 hours.
When it comes to drinking coffee, keeping your chronotype in mind is important. If you consume it when your cortisol levels are already elevated, you push your body’s stress response beyond healthy limits which can have negative consequences for your health. Drinking coffee when your cortisol levels are at their lowest will help to balance your energy levels and mood so you get the extra boost when you need it most.
Wondering what time that is? Your cortisol levels are highest in the morning when you wake up, peaking within a couple of hours after waking. You also have small spikes that correspond with meal times around noon and 6 pm.
Experts believe the best time to drink your coffee is in between your early morning and noon spike to prevent excess stress on the body or wakefulness at night. If you’re an average riser, this means you should drink your coffee between 10 and noon. If you’re an early or late riser, waiting 2-3 hours after you wake up is ideal.
Waiting to drink your coffee also means you’re less likely to have too much of it, preventing you from experiencing issues with sleep that evening. A study performed in 2013 found that caffeine was linked to sleep disturbances up to 6 hours after consumption, reducing total sleep hours and sleep quality.
Regardless of your individual chronotype, caffeine is a stimulant that has the potential to disturb your sleep at night. If you have a genetic predisposition towards sensitivity, the effects of could be so severe that it causes insomnia many hours later. Excesses of the chemical intake even in individuals without genetic sensitivities can also lead to unwanted wakefulness.
According to Matthew Walker, Ph.D., the director of The Center for Human Sleep Science and author of the bestselling book Why We Sleep, “[Caffeine] is one of the most common culprits that keep people from falling asleep easily and sleeping soundly thereafter, typically masquerading as insomnia, an actual medical condition.”
Caffeine can make it harder to fall asleep at night, decrease slow-wave sleep, and interrupt sleep during the night.
Four caffeine-induced psychiatric disorders are currently recognized by the DSM-IV, the diagnostic manual of the American Psychiatric Association (DSM-IV) – caffeine intoxication, caffeine-induced anxiety disorder, caffeine-induced sleep disorder, and caffeine-related disorder not otherwise specified. Caffeine-induced sleep disorder results from too high of a dose or a sensitivity/intolerance to its effects.
To be diagnosed with this condition, the following criteria must be met:
DSM-IV Criteria for Caffeine-induced Sleep Disorder
- A prominent disturbance in sleep occurs that is sufficiently severe to warrant independent clinical attention.
- There is evidence from the history, physical examination, or laboratory findings that the sleep disturbance is the direct physiological consequence of caffeine consumption.
- The disturbance is not better accounted for by another mental disorder.
- The disturbance does not occur exclusively during the course of a delirium.
- The disturbance does not meet the criteria for breathing-related sleep disorder or narcolepsy.
- The sleep disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
Source: “Caffeine – Induced Psychiatric Disorders” – Francis M. Torres 
Thankfully, when it comes to caffeine-induced sleep problems, the treatment is simple – scale back on or quit!
Tips For Sleeping Better After Caffeine
Whether you’re an athlete using caffeine to improve your performance or a college student pulling an all-nighter to cram for an upcoming exam, sometimes caffeine is a must. No judgment here, we’ve all done it! But is there a way to counteract some of the negative side effects so you can catch up on some well-earned zzz’s?
Here are the top 5 tips for getting to sleep after too many caffeinated stimulants.
Drink Coffee Earlier
If you need to drink a caffeinated beverage, try to do so earlier in the day or at least 8-10 hours before you plan to go to sleep. This gives it enough time to get out of your system so you can fall asleep at night.
If you do drink coffee or another caffeinated beverage, be sure to follow this with plenty of water. The effects of caffeine will be heightened in a dehydrated state, so improving hydration will help to clear it from your body more quickly.
Know Your Caffeine Limits
Use a caffeine calculator to figure out your own safe daily dose and stay within it. Trouble sleeping is one of the biggest symptoms of caffeine overdose, so know your limit and stick to it.
Take a Supplement
L-Theanine and Vitamin C have both been found to help counteract some of the negative effects.
Move Your Body
Exercising can also help to metabolize caffeine more quickly and clear it from your system.
A world without coffee would be a very scary place full of very grumpy and zombie-like individuals. There’d be an increase in car accidents, much more divorce, and likely higher death rates due to errors in the workplace! Let’s face it, coffee makes the world a better place!
Like all drugs, caffeine can have some serious side effects, especially if you’re part of the population that’s more sensitive to it. With a few adjustments in when and how much you drink, coffee and sleep can co-exist. So grab your cup of joe and take that first gratifying sip – just be sure to drink it all before noon!
RN, RHN, Certified Health Coach
Raina Cordell is a Registered Nurse, Registered Holistic Nutritionist, and Certified Health Coach, but her true passion in life is helping others live well through her website, www.holfamily.com. Her holistic approach focuses on the whole person, honing the physical body and spiritual and emotional well-being.
Sources and References:
 Caffeine Consumption Habits and Perceptions among University of New Hampshire Students – Nicole L. Olsen, University of New Hampshire Scholars’ Repository
 How Much Caffeine Is in Your Drinks – The Diabetes Council
 Trends in caffeine intake among US children and adolescents – Pediatrics, Official Journal of The American Academy of Pediatrics
 The Absolute Bioavailability of Caffeine in Man – J. Blanchard, S. J. A. Sawers – European Journal of Clinical Pharmacology
  Interindividual differences in caffeine metabolism and factors driving caffeine consumption – Astrid Nehlig, Stephen P. H. Alexander, Pharmacological Reviews
 Genetics of caffeine consumption and responses to caffeine – Yang A1, Palmer AA, de Wit H. – Department of Psychiatry & Behavioral Neuroscience, University of Chicago
 Coffee, caffeine, and sleep: A systematic review of epidemiological studies and randomized controlled trials – Clark Ian, Landolt Hans Peter – University of Zurich
 Antioxidant and antiradical activity of coffee – Alexander Yashin, Yakov Yashin, Jing Yuan Wang, and Boris Nemzer – PubMed, US National Library of Medicine, National Institutes of Health
 Long-term coffee consumption and risk of cardiovascular disease: a systematic review and a dose-response meta-analysis of prospective cohort studies – Ding M, Bhupathiraju SN, Satija A, van Dam RM, Hu FB – PubMed, US National Library of Medicine, National Institutes of Health
 Caffeinated and decaffeinated coffee consumption and risk of type 2 diabetes: A systematic review and a dose-response meta-analysiss – Ming Ding, Shilpa N. Bhupathiraju, Mu Chen, Rob M. van Dam, and Frank B. Hu – Diabetes Care, American Diabetes Association
 Epidemiologic evidence on coffee and cancer – Lenore Arab, Nutrition and Cancer Journal
 Differential effect of caffeine intake in subjects with genetic susceptibility to Parkinson’s Disease – Prakash M. Kumar, Swe Swe Thet Paing, HuiHua Li, R. Pavanni, Y. Yuen, Y. Zhao & Eng King Tan – Scientific Reports
 Caffeine as a protective factor in dementia and Alzheimer’s disease – Eskelinen MH, Kivipelto M. – PubMed, US National Library of Medicine, National Institutes of Health
 Caffeine intake is related to successful weight loss maintenance – D Icken, S Feller, S Engeli, A Mayr, A Müller, A Hilbert & M de Zwaan – European Journal of Clinical Nutrition volume
 Association of coffee consumption with all-cause and cardiovascular disease mortality – Junxiu Liu, Xuemei Sui, Carl J.Lavie, James R.Hebert, Conrad P.Earnest,Jiajia Zhang, Steven N.Blair – Science Direct
 Caffeine – Induced Psychiatric Disorders – Francis M. Torres – American Medical Technologists