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Sleep Health

Caffeine And Sleep: How Long Coffee Stays In Your Body

  •  Purple Author Icon
    Last Updated
    July 28, 2022
    min read

    Caffeine is a ubiquitous part of modern life. Whether it’s in coffee, sodas, or energy drinks, caffeine consumption has become essential in getting people through the daily grind. But caffeine impacts your health in ways you might not even be aware of, especially when it comes to sleep.

    There’s no hard and fast rule when it comes to caffeine’s longevity in your body, but there are some basic principles you can start with and adjust according to your lifestyle. From controlling your intake to sticking to a caffeine schedule, there are many ways to consume caffeine without affecting your sleep patterns. 

    Learn how to retain your productivity throughout the day while getting restful sleep at night in our comprehensive guide to sleep and caffeine.

    How Does Caffeine Work?

    Since caffeine is a stimulant, it blocks the reception of adenosine, a neurotransmitter that triggers your brain’s response to exhaustion. With caffeine intake, the body temporarily puts adenosine on hold until the caffeine wears off. This means that the longer you’re awake, the more adenosine gets built up in the brain. 

    However, caffeine only binds the adenosine receptors temporarily. This explains the burst of energy you feel after caffeine intake and the crash after it wears off. 

    How Does Caffeine Affect Your Body?

    Your caffeine intake may impact your brain and overall health. Let’s break down these side-effects below.

    Negative Impacts On The Brain

    While it can help you focus, too much caffeine can also induce anxiety and stress. Extended periods of caffeine dependence can have lasting effects on your brain, ranging from sleep disorders and sleep deprivation to a disruption of your circadian rhythm – the body's natural 24-hour cycle for rest and activity.

    Some of the long-term effects of caffeine consumption involve the disruption of restorative sleep, which is the period in which the brain cleans itself. High adenosine levels often go together with caffeine dependency, leading to a vicious cycle of needing more caffeine to perform tasks.

    Negative Impacts On Overall Health

    Caffeine triggers your body’s "fight or flight" response. This means that it puts the body into a temporary state of overdrive, which might explain the surge of energy you feel when doing physical tasks after having an energy drink. This is not necessarily bad, but repetitively tricking the body into this state can be bad for the body. 

    The following symptoms have been found to occur in cases of high caffeine consumption:

    • Diarrhea
    • Excessive sweating
    • Nausea
    • Increased heart rate and blood sugar levels
    • Muscle tremors
    • Dilated pupils
    • Sweaty palms

    These negative effects could prove dangerous for those with comorbidities. If you run the risk of hypertension or gastric disorders, it would be best to limit your exposure to caffeine. However, healthy adults who take a regular dose of caffeine have nothing to worry about, as long as they get adequate sleep.

    How Long Does Caffeine Stay In Your Body?

    While there are different degrees of caffeine sensitivity based on your genetic make-up, research shows that the maximum effects of caffeine can be felt within 30-60 minutes from ingestion. Within fifteen minutes, almost 95% of caffeine in coffee will have been absorbed by your body. After four to six hours, it will have completely dissipated from your system.

    Of course, this is just an estimate – different people metabolize caffeine at different rates. In a study conducted by Harvard University, over 120,000 people were observed and found to have six genetic variations for metabolizing caffeine. These variations ranged from mild affectation to addiction. 

    How Does Caffeine Affect Sleep?

    Caffeine can have disruptive effects on your sleep quality if consumed too close to bedtime. Effects on sleep can include restlessness, insomnia, and feeling tired even after a full night's worth of rest. 

    A community-based study has shown that across age groups, caffeine decreased the quality of sleep in terms of efficiency and duration and delayed slow-wave sleep and REM sleep. Particularly, the same study cited middle-aged adults being more negatively affected by an increased intake of caffeine. 

    Having the right mattress can make all the difference. Purple mattresses feature the GelFlex Grid which cushions and supports you while dissipating body heat.  

    Can Caffeine Keep You Awake?

    Yes. Caffeine is best known for keeping you awake for extended periods. Specifically, it maintains an alert level of brain activity by blocking off adenosine, a neurotransmitter that signals exhaustion to your brain. Caffeine can also briefly heighten your concentration and reflexes.

    Does Caffeine Cause Insomnia?

    Late-night cups of coffee certainly won't help you get any sleep at night, but caffeine isn't the only cause of insomnia. 

    The time of consumption, lifestyle, diet, age, and gender can all contribute to insomnia. Additionally, it may become harder to sleep the more you're dependent on caffeine. 

    How Can I Tell If Caffeine Is Affecting My Sleep?

    Our sleep follows what is known as the Circadian Rhythm, which regulates the natural 24-hour sleep-wake cycle of your body. This means that your natural sleep pattern flows with your level of activity and the progression of your day from morning to night.

    Since caffeine keeps you awake, it can disrupt this natural cycle of rest. Some effects include frequent awakenings throughout the night, increased energy levels during rest time, and overall sleep disturbance.

    Caffeine also affects the different stages of sleep, which provide varying health benefits at every stage. According to the US National Institute for Neurological Disorders and Stroke, the most important one is known as the slow-wave sleep stage. The same institute cites that caffeine consumption and dependency can drastically reduce the amount of time you spend in this stage.

    If you’re chronically sleep deprived, you may be at risk of a sleep disorder. Take our quick “are you sleep-deprived” quiz to find out more!


    Sleeping Tips For Caffeine Lovers

    Limit Your Intake

    Health experts suggest maintaining a moderate consumption of caffeine per day, about 3-4 eight-ounce (250mL) cups of coffee, or its equivalent in soft drinks. It's also important to taper off the intensity of caffeine intake as you get closer to your nocturnal sleep time. 

    Limiting your intake doesn’t necessarily mean cutting back completely. Try to be smart about your caffeine intake by transitioning to alternatives like hot cocoa or ice cream in the latter part of the day. 

    Take A Nap

    Another way to be smart about your caffeine intake is to immediately take a short power nap after having a cup of coffee. There’s a way to take the perfect “coffee nap”, but it might take a little practice to get it right. 

    Stay Hydrated

    Drinking water helps soften the bad side effects, as even a single dose of caffeine is heightened when the body is in a state of dehydration. This might explain the "wired" feeling you get after a big serving of coffee. Drinking water also ensures that caffeine dissipates at an evenly balanced rate, which can make it easier to fall asleep.

    Drink Coffee Earlier

    After you first take a sip of coffee, caffeine immediately halves after about 45 minutes. On average, it will take about 4-6 hours before fully dissipating. 

    With this in mind, you can set up a workable schedule for your caffeine intake as best fits your lifestyle. A good rule is to have no hard sources of caffeine after 2 P.M. and to taper off towards softer sources like tea as you approach the hours before bed.

    Take Supplements

    Some supplements are known to offset or, at the very least, cushion the impact of caffeine consumption. A daily dose of L-theanine and vitamin C goes a long way when coupled with exercise and a balanced diet. Apart from vitamins, there are different kinds of food you can incorporate into your diet for better sleep

    Exercise And Move Your Body

    Maintaining an active lifestyle ensures you don't put the extra burst of energy and focus from caffeine to waste. By exercising regularly, your body metabolizes and clears the caffeine from your system faster. 

    Try Decaf 

    Even if there's no such thing as fully decaffeinated coffee, having decaf in the later parts of the day can be beneficial for those who truly need the coffee fix. The level of caffeine in decaffeinated coffee is significantly cut down and is almost at level with tea leaves. What's more, decaf can be a crucial step in the right direction for those who are caffeine dependent.

    Frequently Asked Questions On Caffeine And Sleep

    Why does coffee sometimes make me feel tired?

    That "wired" feeling you get after a cup usually means the activity of coffee is wearing off and the built-up adenosine is taking over. Always remember that having caffeine does not necessarily eliminate the feeling of exhaustion or sleepiness but merely puts it off for a short while.

    If you absolutely have to get through a deadline or pull off an all-nighter, you can cushion these bad side effects by drinking water and resting once you start to feel tired.

    How much caffeine is safe to drink?

    The FDA recommends around 400 mg of caffeine or about 4-5 cups of coffee a day as a safe amount for consumption. Try to keep the cups average-sized or small, as a large cup of coffee will contain around 470 mg of caffeine.

    Why do I sleep better after drinking coffee?

    One of the unforeseen benefits healthy caffeine consumption can have is that it improves your sleep quality. As the caffeine wears off, your adenosine levels start to rise, leaving you tired. 

    The best way to sleep after drinking coffee is to not have too much and taper off your caffeine consumption throughout the day.


    About the authors

    Purple Staff
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