How Caffeine Affects Sleep

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Everyone responds differently to caffeine, which is why you probably know people who can drink an espresso after dinner and go to bed with no issues, as well as people who will be up all night if they have so much as a sip of Diet Coke past 9 AM.

A quick primer on the basics: Caffeine is a stimulant found in things like coffee, tea, chocolate, some sodas, and some over-the-counter medications. The FDA categorizes caffeine as both a food additive and a drug. People typically use caffeine to help them wake up in the morning or remain alert when they are groggy or sleepy.

Because it’s a stimulant, caffeine can affect how and when you sleep. Here’s everything you need to know about caffeine and sleep.

[Editor’s Note: The information provided should not be considered a substitute for professional advice. Please consult a sleep doctor or other medical expert if you have questions related to your own health.]

Basically, caffeine works by stealthily fooling your body.

Caffeine looks a lot like a neurochemical called adenosine. Lucas Reilly from MentalFloss explains: “As your neurons fire throughout the day, a neurochemical called adenosine builds up in your body. The nervous system uses special receptors to monitor your body’s adenosine levels. As the day wears on, more and more adenosine passes through those receptors—and it makes you sleepy. It’s one of the reasons you get tired at night.”

Caffeine tricks those receptors by “docking” at the receptors usually reserved for adenosine. So real adenosine molecules can’t enter, and you don’t get tired as quickly.

Binge-Watching TV Is Hurting Your Sleepamenic181/Shutterstock

Caffeine also works fairly fast.

According to The National Sleep Foundation, caffeine enters the bloodstream when absorbed in the stomach and small intestine — and the foundation says it “can have a stimulating effect as soon as 15 minutes after it is consumed.” The FDA estimates that caffeine typically reaches its peak level in your bloodstream within one hour of consuming it, and stays in your bloodstream for four to six hours.

There’s no nutritional need for caffeine in your diet.

You absolutely don’t need it to keep your body fueled and healthy. Because there is no nutritional need for them, caffeinated products are not recommended for young children.

Side effects of caffeine can also affect your body—and your sleep.

Some side effects include anxiety, a racing heart, and digestive issues, none of which are conducive to good sleep. Caffeine is a diuretic, meaning it increases the frequency of urination. So, too much caffeine may put your bladder into overdrive, further interrupting your sleep.

andrew crotty/Shutterstock

Plus, caffeine causes a physical dependence—and withdrawal is real.

Common caffeine withdrawal symptoms include headaches, sleepiness, irritability, and trouble focusing. “If you want to stop caffeine use… you should taper yourself off instead of going cold turkey because that will help avoid some of the classic symptoms including headache,” Dr. Stacey Sigmon, Ph.D. told ABC Science in 2009.

So, experts recommend consuming it in moderation.

Currently, the FDA says that for healthy adults, 400 milligrams a day (which is four or five 8oz cups of coffee) is “an amount not generally associated with dangerous, negative effects.” The American Pregnancy Association recommends that pregnant women consult their doctors about their caffeine intake, but offer a general guideline that pregnant women should aim to stay below 200 mg of caffeine each day (which is about one 12oz cup of coffee).

Ultimately, you should be mindful of how caffeine affects you personally, and tailor your caffeine habits for optimal sleep.

The National Sleep Foundation recommends avoiding caffeine “close to bedtime.” But if you know you’ll feel alert for ages after drinking coffee, maybe set yourself a daily caffeine cut-off of lunchtime or earlier. You can also make smart swaps by opting for decaffeinated coffee, tea, and soda in the evenings. If you are having trouble sleeping, try cutting down on caffeine to see if that makes a difference. And if you’re worried about any aspect of your diet, including caffeine consumption, chat with your doctor and see what they recommend.

You can also make smart swaps by opting for decaffeinated coffee, tea, and soda in the evenings. If you are having trouble sleeping, try cutting down on caffeine to see if that makes a difference. And if you’re worried about any aspect of your diet, including caffeine consumption, chat with your doctor and see what they recommend.

[Editor’s Note: The information provided should not be considered a substitute for professional advice. Please consult a sleep doctor or other medical expert if you have questions related to your own health.]

Featured image: FOOKPHOTO.COM/Shutterstock

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Joe Auer

Joe Auer is the editor of Mattress Clarity. He mainly focuses on mattress reviews and oversees the content across the site.

He likes things simple and take a straightforward, objective approach to his reviews. Joe has personally tested nearly 250 mattresses and always recommends people do their research before buying a new bed. He has been testing mattresses for over 5 years now, so he knows a thing or two when it comes to mattress selection. He has been cited as an authority in the industry by a number of large publications.

Joe has an undergraduate degree from Wake Forest University and an MBA from Columbia University.