The key is timing and quantity, not cutting it out completely.
Reviewed by Dietitian Katey Davidson, M.Sc.FN, RD, CPT
Key Points
- Dietitians recommend avoiding caffeine at least six hours before bed for better sleep.
- Caffeine can reduce deep sleep and overall sleep quality, leaving you less rested the next day.
- Watch for hidden caffeine and other stimulants in foods, drinks and supplements.
When it comes to sleep, dietitians don’t mess around. They know the powerful effects of having a good night’s rest. From skipping heavy meals before bed to steering clear of alcohol, there’s plenty they do to promote better sleep.
But there’s one thing that almost every dietitian does, and while it may seem obvious, it has a significant impact on how well you sleep: avoiding caffeine too close to bedtime.
Keep reading to find out why dietitians avoid caffeine for better sleep—and why it matters more than you might think.
It Takes Longer to Fall Asleep
It’s 1 a.m., you’re tossing and turning and begging your brain to just shut off so you can finally fall asleep. As you mentally rewind your day, you land on the likely culprit: that regular caffeinated latte you polished off after 4 p.m.
Elizabeth Shaw, M.S., RDN, CPT, explains why caffeine can interfere with you drifting off into a blissful sleep: “Caffeine works by blocking adenosine, a natural compound that signals to your body that it’s time to wind down and sleep.” Once blocked, you feel less tired, making falling asleep a lot more challenging.
Research shows that caffeine increases the time it takes to fall asleep by an average of 9 minutes and reduces total sleep time by about 45 minutes. While 9 minutes may not sound like much, losing close to an hour of total sleep can leave you feeling far from refreshed the next day.
It Can Make It Hard to Relax
When caffeine blocks adenosine, it also indirectly affects neurotransmitters that can keep you wired, says Mandy Enright, M.S., RDN, RYT. Dopamine and serotonin—often referred to as the “feel good” hormones—get a boost, causing you to feel more alert and stimulated. At the same time, gamma-aminobutyric acid (GABA), a neurotransmitter with a naturally calming effect, also gets suppressed. The result? A brain that’s wired instead of winding down.
Caffeine can also temporarily raise blood pressure and increase heart rate, making it harder for your body to relax, Enright adds.
It Stays in Your System Longer
Although you may only feel the effects of caffeine for a few hours, it actually lingers in your system much longer than you may think. “The half-life of caffeine averages about five hours, meaning it can take that long for it to leave your system,” says Enright.
Factors like genetics, pregnancy and certain medication can slow that process even further. That’s why your friend or partner may be able to sip a late-afternoon coffee with no problem, while you’re wide awake at midnight counting sheep. We all metabolize caffeine differently.
It May Cause You to Wake Up More Frequently
Let’s say you successfully dozed off, but suddenly wake up in the middle of the night. What’s that about? Drinking caffeine too close to bed can also make it harder to stay asleep.
“Research shows caffeine can increase wakefulness and arousals during the night while reducing sleep efficiency, so even if someone appears to get enough hours, they may wake more often and feel less rested in the morning,” explains Patricia Bannan, MS, RDN.
Here’s why: Caffeine can change sleep quality by keeping the brain in a more alert, easily aroused state, which can make sleep lighter and more fragmented, shares Bannan. Studies have found caffeine can add roughly 12 minutes of middle-of-the-night wakefulness.
It May Reduce Sleep Quality
Picture this: You’ve slept a full night but don’t feel that well rested. Drinking caffeine too close to bedtime can also impact the quality of sleep.
“Even if you do fall asleep, your sleep schedule can become disrupted. You may spend more time in lighter stages of sleep, reach REM later or get less of it overall,” explains Shaw. “This matters because REM sleep is essential for learning, cognitive performance, emotional regulation and more. When you’re not getting enough of it, it can take a toll on your mental, physical and cognitive health over time.”
Research shows that caffeine can alter sleep stages, increasing lighter sleep by about 6 minutes while reducing deep sleep by over 11 minutes. “When REM [sleep] gets cut short, people may notice more brain fog, poorer concentration or simply feel less restored the next day,” adds Bannan.
Your Food or Drink May Contain Other Sleep-Disrupting Ingredients
It may not just be the caffeine that’s interfering with your sleep—other ingredients also matter.
“Some [products] also contain added stimulants, such as guarana, that can increase the overall stimulating effect and make sleep disruption more likely,” shares Bannan. Other ingredients like B vitamins, large amounts of added sugar and taurine may also play a role.
In particular, energy drinks and specialty coffees tend to be high in added sugar, which can cause a rapid rise in blood sugar followed by a crash shortly after, explains Shaw. “This kind of blood-sugar roller coaster isn’t ideal if you’re trying to get quality sleep and wake up feeling rested for the week ahead,” she adds.
After-dinner treats may also be a hidden sleep disruptor. Even small amounts of caffeine can have an impact. For example, 1 ounce of dark chocolate contains 23 milligrams of caffeine—roughly equivalent to about a quarter-cup of coffee.
That’s why it’s worth taking a closer look at your favorite beverages, snacks, supplements or even electrolyte powders, as many may contain caffeine, along with stimulants and energizing vitamins.
Dietitian-Approved Tips for Better Sleep
- Set a Caffeine Cutoff Time. For many people, avoiding caffeine for at least six hours gives your body enough time to metabolize it. For sensitive sleepers, even earlier may be better, says Bannan. Though, everyone’s individual limits and tolerance vary.
- Give Yourself Time to Unwind. Some days may feel like nonstop chaos right up until you hit the pillow, but try to build a wind-down routine into your evening to help your body relax and prepare for bed. “Light stretching, doing a skin-care routine or listening to music to allow the brain time to unwind with you,” advises Enright.
- Avoid Screens at Least One Hour Before Bedtime. It’s easy to fall into the habit of scrolling once you get into bed, but putting down your phone and stepping away from the TV, laptop or tablet can make a big difference in helping your body and mind unwind and ease into sleep, says Shaw.
- Dim the Lights. Lowering the lights helps trigger the production of melatonin, a hormone that regulates your 24-hour clock. As evening approaches, try using lamps or dimming the lights to prepare your body for sleep.
- Enjoy a Calming Beverage. Skip the caffeine and reach for herbal tea (which is naturally caffeine-free), warm milk or tart cherry juice. Tart cherry juice naturally contains melatonin, a hormone that supports the sleep-wake cycle, says Enright.
Our Expert Take
Dietitians recommend limiting caffeine to earlier in the day to support better sleep. Caffeine can make it harder to fall asleep, may cause more nighttime wake-ups and reduce deep and REM sleep quality.
Instead, they recommend setting a caffeine cut-off time of at least six hours before bedtime, building in a wind-down routine, limiting evening screen time, dimming the lights and enjoying a relaxing nighttime beverage. These small changes can be the answer to logging more zzz’s.
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