Ever drank a giant cup of coffee and still felt tired? Or sipped a green tea after dinner and had the worst sleep of your life that night?
The effects of caffeine on our sleep is an incredibly interesting topic, and not as simple as you may have thought. So, we’ve created this concise article (no long, boring, or complex paragraphs!) to explore it a little further.
You might find out just why caffeine makes it harder for you to sleep (or easier) and how you can manage your caffeine intake throughout the day to stay awake when you need to and sleep like a rock when your head hits the pillow.
How Much Do We Know?
We know that sleeping every night is essential for good health. We know that not getting enough sleep has some terrible consequences for your mental and physical health. And yet, we don’t actually know why we sleep.
Furthermore, the science of nutrition tends to be quite messy. We have so much data to explore, learning about how our bodies use nutrition and their effects on everything, including sleep. But we still publish contradicting articles. Is an egg a day good for your health, or could it cause cancer?
Without locking people up and strictly monitoring their every move, bite and sip, we can’t know for definite the long-term effects of caffeine on our sleep and general health. Instead, the current advice we’ve got is based on observing people consume caffeine and their sleep, without controlling the numerous variables of life. Much more ethical… but far harder to draw a reliable conclusion.
We’re pointing this out because you need to make an informed decision, and how can you do that if you don’t know what to believe. So, we’re going to give you the facts about caffeine and sleep that we know.
Just don’t expect it to be as simple as “don’t drink black tea 2 hours before bed”. One brand of tea may have a drastically different amount of caffeine compared to another. And then there are your personal characteristics – are you extra sensitive to caffeine? Do you have a fast metabolism?
All of this pulls together to make it very difficult to calculate how caffeine will affect you. Specifically, you.
Basically, take things with a pinch of salt. And, if you’re keen to find out exactly how much caffeine you should drink and how it will impact your sleep, be prepared to get hands-on and put these facts to the test.
How Caffeine Affects the Ability to Fall Asleep
Considering that if you lose just 1.5 hours of sleep a night, you’ll reduce your alertness the next day by roughly one third, getting enough sleep and regulating your caffeine intake is seriously important!
Caffeine is a stimulant. It works by:
- Blocking adenosine receptors (stopping the sleep-inducing chemicals from binding to our brains),
- Increasing adrenaline production to give us that burst of energy and motivation.
With too much adrenaline and not enough adenosine, we are alert and very awake, thus making it hard to fall asleep.
When caffeine is at its peak in your body, it will be very difficult to feel sleepy and fall asleep – although not impossible. However, it takes approximately 15 to 60 minutes for the caffeine to kick in, giving you a small window between chugging that cup of coffee and the alertness that follows to possibly fall asleep.
Furthermore, caffeine has a half-life of roughly 6 hours. At this point, half of the caffeine is out of your system, while the rest lingers on. It’s at this half-life that the notable caffeine effects will be mostly worn off. You won’t feel as alert or energetic. You may even have crashed.
So, if your desired bedtime is 10 pm, you shouldn’t be consuming any caffeine after 4 pm – there goes your after-dinner coffee! There’s also evidence to suggest that the older you are, the longer the caffeine stays with you.
Long Term Effects
Another study found that consuming coffee can delay your circadian rhythm, AKA your body clock.
One cup of coffee can shift things around by 40 minutes, delaying sleep. While that doesn’t sound too positive, it could be beneficial. Scientists who conducted the study concluded that caffeine could be used for jet lag, where shifting or resetting your circadian rhythm back to normal for your time zone would be a good thing!
The other long-term side effect of caffeine is dependency and that awful caffeine crash. Regularly consuming caffeine gets you into that cycle of feeling dead tired until you get your first cup of the day. The dangers here are that over time you are less responsive to caffeine, so you need to “up your dose” to feel the effects.
Consuming vast amounts of caffeine like this can have nasty side effects, from an erratic heart rate to muscle tremors, not to mention how it can disrupt your sleep pattern as you push back your bedtime every evening.
The Quality of Sleep After Consuming Caffeine
This is a hard one to calculate. One study into how caffeine affects sleep quality found that those consuming a high amount of caffeine during the day were more likely to feel tired the next day, even after sleeping. But the problem is, are they drinking a high volume of caffeine because they’re naturally tired every morning, or did the caffeine cause it by disrupting their sleep quality?
We enter a “chicken or the egg” scenario with a coffee cycle of consuming caffeine where we are tired and feeling tired because of the caffeine.
To complicate matters further, an Ecuadoran study on a village that had very few variables (no light pollution, noise pollution, fast food, etc.) concluded that caffeine had little or no impact on sleep patterns.
Ultimately, the study into caffeine and sleep quality concludes that:
Further research, particularly with (necessarily rare) caffeine-naive populations, is required to elucidate the complexities of the relationship between caffeine, sleep, and daytime functioning.
With a high variability between one person and the next when it comes to caffeine sensitivity, plus the placebo effect of knowing that caffeine impacts your sleep, it’s hard to say for sure exactly what caffeine does. There are also other ways that caffeine could impact your sleep. If you suffer from acid reflux, for example, drinking acidic coffee late in the evening could flare up your esophagus as you’re trying to sleep.
All we can say is, consuming caffeine does (in one way or another) impact sleep patterns and daytime alertness, which is why limiting your caffeine intake is considered healthy. Scientists are simply struggling to pinpoint the how and the why.
Before we dig into how much caffeine you can safely consume, here are some extra tips to make sure your sleep is deep and uninterrupted.
What Else Could Be Affecting My Quality of Sleep?
- The type of caffeinated beverage you consume. Green tea, for example, contains amino acid l-theanine and GABA, which have been proven to improve both sleep quality and length despite the caffeine content.
- Other nutrients you are consuming. Foods high in serotonin can cause vivid dreams and nightmares. This includes cheddar, milk, chicken, lamb, and white rice to name a few.
- Bedtime habits. Did you know that blue lights affect your ability to sleep more than any other color? Blue light blocks melatonin in your brain, making it much harder to sleep. This is why some smartphones, tablets, and other electronic devices will have a ‘night light’ or ‘warm light’ setting that mutes blue tones and gives your screen a warmer glow. It’s best to avoid using your electronic devices right before bed – especially if you’re hooked to the very blue and white designs of Facebook and Twitter.
- Sleep environment. It should be dark, quiet, comfortable, and cool, so forget the nightlight and stuffy polyester sheets. Being too hot or in an environment that’s too noisy and bright is just going to diminish your chances.
So, When Is It Safe to Drink Caffeine Before Bed?
The guidelines from the FDA are to consume up to 400mg of caffeine per day – and not a drop more. That’s approximately 4 or 5 cups of coffee or 8 cups of black tea. Guidelines are much lower for pregnant women and children, although you could debate that if you’re a child or pregnant you should be avoiding caffeine as much as possible.
As for how long before bed you can consume caffeine, it depends on you as an individual. To be safe, we’d recommend not consuming caffeine past 3 pm or 4 pm, so levels of caffeine in your system are at least halved before you hit the hay.
If you consume a lot of caffeine and are desensitized to its effects, you may be able to get away with downing your last evening tea or coffee an hour or so before you sleep. Waiting 2 to 3 hours after eating before you go to sleep is generally considered a healthy gap, so why not limit your caffeine to that time frame too?
You should also pay attention to the caffeinated beverage you’re drinking. With energy drinks like Monster and Red Bull, there’s a very exact amount of caffeine per serving. However, with coffee and tea, the level of caffeine in your cup can vary from one variety or brand to another. It will also depend on how long you steep your tea or brew your coffee.
Check out this caffeine database to work out roughly how much caffeine is in your favorite beverages.