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Caffeine is a natural central nervous system stimulant. After consumption, it’s quickly absorbed from the gut into the bloodstream before making its way to the liver. But the organ it most affects is actually the brain since it blocks the effects of adenosine, a neurotransmitter that helps relax you and induce feelings of tiredness. (1)
Caffeine can be found in several common foods and drinks such as:
- Green tea
- Energy drinks
- Dark chocolate
- Chewing gum
Here's how the amount of caffeine varies by caffeinated beverage: (2)
- 8 ounce cup of coffee: 95 - 200 mg caffeine
- 8 ounce energy drink: 70 - 100 mg caffeine
- 12 ounce soda: 35 - 45 mg caffeine
- 8 ounce cup of tea: 15 - 60 mg caffeine
Not-so-fun fact: there’s residual caffeine content in your decaf cup of joe, which is why we recommend Swiss Water, which uses a patented, chemical-free process to gently remove 100% of the caffeine while preserving the coffee beans' original characteristics.
The half-life of caffeine is 5-6 hours (or longer depending on how fast you metabolize it). Sensitivities vary, but because it’s a stimulant, it may cause difficulties in the onset of sleep if it’s still in the body’s system come bedtime.
One study examining the effects of 400 mg of caffeine 30 minutes before bedtime found that it reduced sleep efficiency 5%, prolonged sleep latency (the amount of time it takes to fall asleep) by 12-16 minutes, and reduced total sleep time by 25 - 30 minutes compared to the placebo group. (3)
But caffeinated drinks don't have to be consumed so close to bedtime for them to affect sleep. Even at six hours, caffeine consumption has been shown to possibly reduce sleep time by more than one hour. (4)
While it's long been understood that caffeine promotes wakefulness and disrupts sleep, new research is emerging on just how impactful caffeine is on the human's internal clock, otherwise known as the circadian rhythm. This system is controlled by two factors:
1. Proteins produced in the digestive system based on the timing of meals
2. Hormones produced by the endocrine system based on energy expenditure
Together, the proteins and hormones control our circadian pacemaker, which shoots out signals from the hypothalamus area of the bran—the suprachiasmatic nucleus (or SCN), to be exact. SCN is sensitive to social activity, temperature, and exercise, but nothing is as important as light. That's why circadian rhythms are so closely linked to day and night—and as we now know, caffeine.
In a 49-day study, (5) the consumption of caffeine equivalent to that in a double espresso consumed three hours before bedtime led to a phase delay of the circadian melatonin rhythm by approximately 40 minutes.
This one is unique to coffee, a diuretic that increases the need to urinate. If consumed too close to bedtime, it can cause more frequent bathroom trips that negatively impact sleep quality.
As a rule of thumb, we recommend limiting caffeine intake to before 2pm; however, if you are sensitive to the effects of caffeine and/or typically go to bed around 10pm, you wouldn’t want to consume it after 12-1pm in the afternoon (which we acknowledge can be difficult for those craving an afternoon pick-me-up).
It happens to the best of us. Here’s what we recommend to try and optimize the quality and quantity of your sleep, even after consuming caffeine:
- Prioritize a calming wind-down routine
Excitement or stress prior to bedtime causes an increase in the body’s sympathetic nervous system activation. When this occurs, the autonomic nervous system (ANS) releases stress hormones such as adrenaline and cortisol that circulate blood to vital organs and muscles. Your heart rate and blood pressure increase, your breath quickens, your muscles tense, and beads of sweat form as your “fight or flight” response, which evolved as a survival mechanism to enable people to quickly react to life-threatening situations. When this occurs before bedtime, it can run interference with sleep onset (the ability to fall asleep) and sleep maintenance (the ability to stay asleep) by interfering with melatonin and disrupting our sleep cycle. That’s why a wind-down nighttime routine with less stimulating activities is so important for quality, restful sleep. Here are six science-backed activities to try.
- Listen to white noise, a sleep podcast, ASMR, or a guided mindfulness meditation
Sometimes, you need a little help turning off your mind at the end of a long day. We’ve rounded up the best podcasts to help you get sleepy. They’re all available on Apple Podcasts or Spotify so you can easily tune in and doze off.
- Engage in light exercise
Engaging in movement allows you to wind down at the conclusion of the day, but you want to prioritize low-intensity exercise to avoid getting your heart pumping (which increases core body temperature at a time when it should be dropping in preparation for sleep onset).
- Make sure the bedroom is a cool and comfortable temperature
Uncomfortable sleep environments are physiologically activating and can run interference with the onset and/or maintenance of sleep. During certain sleep stages, our bodies do not thermoregulate as much, so if the environment is too hot or cold, it can lead to sleep disruptions. That’s why we recommend making the bedroom a cool, comfortable temperature.
- Engage in progressive muscle relaxation
Progressive muscle relaxation involves tensing a group of muscles as you breathe in for 4-10 seconds, then relaxing them as you breathe out. Just be sure you’re not tensing to the point of pain or uncomfortable cramping. Relax for 15-20 seconds before moving onto the next muscle group. This will help calm your physical body and, as a result, your anxiety levels.
It’s normal to have trouble sleeping every now and again—especially considering just how many factors play a role (stress, hormones, aging, diet, etc). But how do you know if occasional nights spent tossing and turning are symptoms of a sleep disorder? When does “poor sleep” cross the line into insomnia? What about sleep apnea? We've compiled a list to help you understand the potential causes of fatigue (i.e. low energy) and Excessive Daytime Sleepiness (i.e. fighting to stay awake), which are signs that it’s time to consult a sleep specialist.
If it feels, by all accounts, like you DID get a good night’s rest with sufficient hours of sleep but are STILL feeling tired, this may be why.
What Stage Of Sleep Do You Dream: REM or Deep?
12 Best Podcasts To Help You Fall Asleep
6 Ways Sleep Deprivation Affects Work Performance
Dr. Jessica Shepherd Shares The Most Common Sleep Myths She Encounters
Sleep, Nutrition, Or Exercise: What's Most Important For Weight Loss?
Sleep Deprivation + Men's Health: What's The Connection?
16 Science-Backed Things To Try If You Can't Sleep
The Relationship Between Sleep + Memory