Quick facts on caffeine and sleep:
- Your morning cup of coffee can have anywhere from 100-400mg of caffeine, depending on the bean, brew, and size of cup.
- Caffeine’s half-life (how long it takes to break down by half the amount you took) is anywhere from two to 12 hours, depending on your body’s natural metabolism.
- Too much caffeine — and caffeine close to bedtime — messes with our biological clock, making an intended 10p.m. bedtime become after midnight.
- The recommended cut off time for caffeinated food and beverages is around 8-10 hours before bedtime.
There’s no denying that caffeine can make you feel unstoppable. Like the jumpstart you need for a dead car battery, caffeine gives our mood a buzz and gets us ready to start our day.
“Caffeine is the world's most popular stimulant, and is naturally found in coffee, tea, and dark chocolate,” says Dr. Andrea Paul, a former practicing physician who now advises for health start ups like Illuminate Labs. It also tastes, in a Pavlovian way, like comfort.
As a stimulant, caffeine (temporarily) gives us an immediate increase in alertness and energy, but while it can help us stay awake and remain focused on a task, consuming too much caffeine can be problematic. While small amounts can create jittery shakes, irresponsible consumption can lead to substance dependency, and the disruption of our body’s natural rhythms, including our sleep, if we’re not mindful of how and when we take it.
What exactly is caffeine and how does it affect me?
Millions of people rely on caffeine to keep them alert and going, with the CDC reporting that approximately 80% of U.S. adults consume it every day, so let’s demystify it a bit.
Caffeine is a natural psychostimulant found in foods and plants, including coffee beans, tea leaves, cacao, and guaraná seeds, which means you’re likely to find it in your favorite Starbucks drink and even in your morning green tea. While these natural caffeine sources are well-known, there’s also chemical-based synthetic caffeine that’s added to “energy boosting” drinks.
“[It] acts as a stimulant in our brain and makes us feel awake and energized,” says Dr. Chelsie Rohrscheib, a neuroscientist and sleep specialist.
Caffeine is absorbed into the bloodstream about 30 to 60 minutes after consumption. It gets metabolized in the liver and is distributed throughout your body, from the tissues to the brain.
How long does caffeine stimulation last?
A morning cup is routine but giving into an afternoon espresso to stave off that drowsy feeling could impact your sleep hygiene on the same night.
“Caffeine’s effects can last up to 10 hours in your system,” says Jeff Kahn, CEO and co-founder of Rise Science, a sleep tracking app. This extended effect is because caffeine’s half-life is about five hours.
Here’s how half-life works: So, say you have a latte at noon — by 5 p.m. you’ll still have half of it in your system, and by 10 p.m. you’ll have a quarter of the stimulant remaining. For more caffeine-sensitive folks, this quarter amount could be enough to delay sleep by a few hours.
That said, half-life can also take anywhere from two to 12 hours, depending on your body’s natural metabolism.
Your brain and body on too much caffeine
Caffeine binds to these adenosine receptors, explains Kahn, curbing your grogginess and reducing the time your body spends in sleep inertia — that foggy feeling you experience after waking.
“It boosts your energy by blocking the adenosine receptors in the brain so that you don’t feel as much sleep pressure [a biological process that makes us feel sleepy],” he says.
In fact, one study found that caffeine can boost cognitive function in severely fatigued people. So, if you’ve pulled an all-nighter, you’ll have a temporary mental boost after that first cup. That said, if you go overboard with your caffeine intake, you’ll start to experience problems falling asleep.
According to Rohrscheib, too much caffeine messes with our biological clock by extending our circadian rhythm by a couple of hours. For example, if you have a bedtime of 10 p.m., then you might find yourself tossing and turning until about midnight, making that your new bedtime after consuming caffeine in the afternoon or evening.
“While caffeine may offer a short energy boost [in the morning],” Rohrscheib explains, “it can cause your energy levels to crash later in the day, especially if it's affecting your sleep.”
Other research has shown that large doses of caffeine late in the evening may delay your REM cycle and make you feel more exhausted in the morning. Which means even if caffeine doesn’t alter your sleep schedule, it could mess with your sleep quality.
Symptoms of too much caffeine
Ever grab a cuppa at a new place only to experience jitters and anxiety? That’s a sign their coffee might be stronger than your usual, giving you too much caffeine. Over time too much caffeine may create long-term symptoms, such as:
- increased stress levels or nervousness
- poor mood
- stomach issues
- muscle tremors
- inability to control urination
- sleep problems, such as insomnia or ignoring sleep deprivation
For some people, the symptoms above may also appear with withdrawal symptoms, but caffeine withdrawal is more likely show up as headache, fatigue, and difficulty concentrating.
Rohrscheib also notes that excessive caffeine consumption has been shown to disrupt our hormones, which can in turn exacerbate pre-existing conditions or symptoms. “It temporarily raises the level of the stress hormone, cortisol, in the blood, which affects stress and anxiety levels and can also alter blood sugar levels,” Rohrscheib says.
One 2012 study also found a link between drinking caffeinated beverages and elevated estrogen levels in women. While this didn’t appear to affect ovulation, researchers recommend exercising caution with long-term caffeine consumption, as variations in estrogen levels are associated with disorders like endometriosis, osteoporosis, and endometrial, breast, and ovarian cancers.
More reason to be more aware of how much you’re taking in each day.
Did you know much caffeine (on average) is in your drink?
If you’ve recently had a slew of sleep issues crop up, you might need to take a better look at how much caffeine you’re taking in each day.
While most health experts recommend sticking to 400mg of caffeine per day, this doesn’t take into consideration individual sensitivities. How your body reacts to your daily brew will depend on the amount consumed and on personal factors like your age, body weight, and how sensitive you are to caffeine.
Here are some examples of everyday beverages and foods containing caffeine:
|Dunkin’ Coffee (large 20 oz)||270|
|Average cold brew (12 oz)||207|
|Starbucks Coffee Frappuccino (13.7 oz)||110|
|Lipton Black Tea (1 bag, brewed)||55|
|Diet Coke (12 oz.)||46|
|Snapple Lemon Tea (16 oz)||37|
|Green Tea (8 oz)||18|
|Dark Chocolate (1 oz)||12|
However, the amount of caffeine in any given food and beverage can vary dramatically, says Kahn. Not only does the bean and cup size dictate how much caffeine there’ll be but how long you brew certain drinks can increase how caffeinated they are as well. For example, cold brews, which are often steeped overnight, have more caffeine than hot brews. Studies looked into comparing black, green, and white teas that are steeped for 1, 3, and 5-minutes and found that caffeine concentration does slightly increase, the longer you steep your tea.
Anxiety, for example, Paul says, can cause someone to notice the effects of caffeine longer than someone without. “Their system is already dealing with regularly elevated levels of stress hormones,” Paul explains. According to the Mayo Clinic, for some people even a little bit will be too much — giving you the jitters for hours or even until the next day.
The Mayo Clinic also reports that caffeine isn’t a good idea for kids. As far as teens go, Paul recommends they limit their intake to one serving of coffee daily at most (around 90 mg caffeine). Similarly, people who are pregnant, trying to conceive, or breastfeeding are advised to speak with their doctors about limiting their caffeine to less than 200 mg daily (about 1-2 cups).
When is the best time to drink coffee?
1. When you wake up
Most experts advise keeping your coffee-drinking to the morning and avoiding caffeine close to bedtime. “Caffeine works best when consumed 1-2 hours after waking,” Rohrscheib emphasizes. “Additional caffeine consumption throughout the day has diminishing returns and is more likely to affect your sleep than help you feel energized after a certain point in the day.”
For early sleepers or those with an early chronotype, Rohrscheib recommends not grabbing that extra coffee mug past noon, or past 3 p.m. for people with a late chronotype (late sleepers).
2. Eight to ten hours before bed
Got chronic sleep issues? A good rule of thumb is to cut out all caffeinated beverages and foods for 8-10 hours before bedtime.
One study suggests that 400 mg of caffeine (roughly 4-5 cups of coffee) can significantly mess with your sleep. If you really like cutting it close, the same researchers gave a recommendation of abstaining six hours before bed.
3. As a booster, not an alertness aid
“[Consuming caffeine] after your unique cut-off time risks interfering with your sleep since caffeine works to block the body’s natural sleep drive,” says Kahn. If you consistently use coffee to compensate for morning exhaustion, this can also lead to a cycle of dependence.
“Regular everyday consumption of caffeine can cause your body to build up a tolerance, lessening the effects of the drug and requiring consumption of more to feel the same effectiveness,” says Kahn.
Restless nights don’t necessarily mean you need to do away with caffeine altogether. Knowing the recommended amount can be the key to making it work for your internal clock.
How to detox from caffeine
Find yourself negotiating an afternoon cup because you “really need it” — and then up late at night with caffeine insomnia? It might be time to consider a caffeine detox to counteract those side effects.
“If your sleep and health is starting to be affected by caffeine consumption, you're experiencing any negative side effects, or becoming too reliant on caffeine to function, it may be time for a detox,” says Rohrscheib. She also cautions that it's important to cut down on caffeine slowly, because like most stimulants, withdrawal symptoms are almost certain.
So if you normally drink four cups, start drinking three, then two, and so on. The point is to reduce your intake gradually. Experts also recommend swapping out caffeinated beverages for herbal teas to counteract dehydration.
Before going cold turkey, however, Kahn suggests doing an inventory of when you’re drinking your coffee. “Maybe you don’t need a detox,” he explains. “Instead, you may need to be more disciplined about when you consume caffeine.”
To find your caffeine comfort zone, Paul recommends weighing the impact of caffeine on both your physical and mental wellbeing. Use a sleep diary to track the impact of caffeine on sleep, and also ask yourself:
- What benefits of coffee do you enjoy?
- What does too much caffeine feel like to you?
- Do you feel like you must have caffeine in order to start your day?
All to say, only you can know when it may be time for a break. If caffeine is leading to regular bouts of anxiety and sleepless nights, Paul warns, you should definitely consider detoxing.
Other health tips for good sleep hygiene and energetic mornings
As the FDA stresses, caffeine isn’t a substitute for restful, restorative sleep. Taking extra time to wind down and sleep earlier could go a long way with having enough energy throughout the day. Hypnosis, for example, can help calm a buzzing mind. You can also try preparing for bed by using essential oils, or jotting down all your worries in a sleep diary before winding down.
In fact, Kahn also points out that you don’t need caffeine to feel good, stay awake and have energy throughout the day. “Caffeine can help you get a jump on the day,” he says, “but drinking it too late can cause you to not get enough sleep, and then need even more caffeine the next day, creating a vicious cycle.”
Here are some additional tips when it comes to using caffeine:
- When making tea, try shortening the brew time to cut down on caffeine content.
- Drink decaf when you need a pick-me-up later in the day (it still contains caffeine, just in smaller amounts).
- If you are extra sensitive to caffeine, avoid it 8 to 10 hours before bedtime.
- Use a fitness tracker or a sleep app to track your sleep debt and analyze the best time to wake, sleep, and when to drink your coffee.
An alternative to a strong cup of coffee, especially if you work from home, is a power nap. Have less than 20 minutes? Try a cold shower, which may be more effective during a heat wave than hot black tea. “Staying awake comes first and foremost from keeping your sleep debt low and staying in alignment with your circadian rhythm,” says Kahn.
Getting more sleep to get over needing more coffee? That’s a formula we can’t argue with.