There’s a powerful tool with the ability to transform your sleep quality. It
gives you more control over how well you sleep than you may have thought possible. It can help resolve sleep issues including insomnia. And it’s not a pharmaceutical.
That tool is the zeitgeber.
The term “zeitgeber” comes from the German word for “time giver” or synchronizer. That may be too many letters for your daily Wordle, but it’s a fitting name — it’s even earned the tongue-in-cheek nickname zzzz-zeitgeber. In sleep science and neurobiology, a zeitgeber refers to an environmental or external cue that can influence your circadian rhythms — outputs of the internal body clocks that run over an approximately 24-hour period. Essentially, our body clocks sync up with external cues, like sunlight, to help keep time.
Despite being well-known among sleep scientists, zeitgebers haven’t really made their way into the mainstream conversation about sleep. But that doesn’t mean you can’t start using them to align your daily habits with your internal clock. Read on to learn how zeitgebers work and how four zeitgebers can boost your sleep.
How do zeitgebers work?
One of the most familiar ways we experience circadian rhythms is through their impact on our sleep-wake cycle. But these rhythms are not just for sleep, according to Alicia Roth, Ph.D., behavioral sleep medicine psychologist at The Cleveland Clinic’s Sleep Disorders Center. Most essential functions and processes that go on in our bodies also operate on internal clocks, including our hormones, immune system, and digestion. “Our organs all run on some sort of timing system,” says Roth.
"Our biological clocks evolved to help our bodies anticipate the most efficient time of day for each system to do its work and to help those systems stay coordinated with one another," explains Azure Grant, Ph.D., scientist-in-residence at Crescent Health.
A master clock inside the body, the suprachiasmatic nucleus (SCN), keeps your circadian rhythms organized. Like an orchestra conductor, the job of the SCN is to keep our many biological clocks aligned and in sync with our 24-hour day. When all the clocks are coordinated and receiving consistent external cues (the zeitgebers), “our bodies work like a symphony playing in tune and in time,” explains Grant.
Light is the SCN’s most powerful influencer, but your master clock also responds to more subtle cues such as when we exercise, eat, and socialize with others. When these zeitgebers are ill-timed, it can put the conductor and musicians out of step.
This can happen when we expose ourselves to blue-light LED screens at night, or we eat a huge meal at 10 p.m., kicking our digestive system into gear when it would otherwise be resting. In response to these miscues, “some of our systems think it’s daytime, whereas others still think it’s nighttime. Everyone gets confused,” says Grant.
“When our biological rhythms are out of alignment, our bodies can’t work their best,” Grant says. “We sleep poorly, and our risk goes up for all sorts of illnesses — cardiovascular disease, stroke, metabolic disease, cancer, infertility. Pretty much everything gets worse as a result of temporal disruption.”
Technology and our modern lifestyle shoulder most of the blame for disrupting our circadian rhythms and worsening our sleep. But you can also help keep your body’s rhythms aligned by intentionally using many of the things you do each day, like going outside, eating meals, exercising, and being social.
“The magic,” says Grant, “is you don’t need to read a book, try a new medication, or take up a new hobby. By making little tweaks to the timing of your everyday activities — doing them at the right time and at the about the same time each day — you can shift everything in the right direction to improve your sleep and your overall health.”
What are examples of zeitgebers?
The zeitgeber: Light
How to work it: Get sunlight first thing in the morning when you wake up.
When it comes to sleep, the most important thing for setting your biological clock is to get sunlight in your eyes when you wake up, says Andrew Huberman, professor of neurobiology at Stanford University School of Medicine.
Put another way, light is the most powerful zeitgeber. The same way you need darkness to cue your brain that it’s time for sleep, your body needs light to set your circadian rhythms to daytime.
Morning light signals the brain to kick off cortisol production and stop melatonin production, letting your body know that your day has started. It doesn't matter whether you're a night owl or an early bird, Huberman says. The important thing is to get some sun for at least a few minutes soon after getting out of bed.
“We were designed to get a lot of ultraviolet light on our eyes during the day and little during the night. The more of these cues to the time of day and night you can give your body, the better off you'll be,” Huberman says.
On the flip side, exposure to artificial bright light and blue light in the evening can interfere with melatonin production and disrupt your circadian rhythms, Grant says. (But you already knew that.)
If you’re still scrolling through your social feeds or email before bed, just stop! Power off electronics about 90 minutes before bed, she advises.
The zeitgeber: Food
How to work it: Eat your meals at about the same time each day. And don’t eat too close to bedtime.
Research shows that mealtimes can affect our circadian rhythm. And it’s not just what you eat but when you eat, says Grant.
With the first bite of food, we signal our digestive system (clocks in the liver, heart, muscles, and kidneys) that it’s time to get to work. According to an article in the Journal of Biological Rhythms, “Your body is best at digesting food and drink when you’re active and light is present.” Eating and drinking when it’s dark out, at a time when your body expects to sleep and rest, can disrupt this system and compromise your metabolism.
“When you eat late at night, your organs have no choice but to ramp up to process the food rather than wind down for rest, which isn’t good for them or conducive to good sleep,” Grant says. Many experts recommend eating within a 12-hour window (for instance, between 8 a.m. and 8 p.m.) to allow your digestive organs enough time to rest.
“Your body thrives on consistency,” Grant says. “A regular daily cycle of eating and fasting may help nurture a healthy circadian clock and optimize metabolism.”
Our bodies can also keep track of time within a single day, cycling over a period of hours, according to Grant.
“This timing system, called ultradian rhythms, hasn’t been studied as much as circadian rhythms have. But to keep those cycles healthy, it’s probably a good idea to follow the same principles and try to eat your meals at the same time each day,” Grant says.
The zeitgeber: Exercise
How to work it: Establish a consistent routine and stick to it, working out the same time every day.
Exercise can help coordinate or entrain your circadian clocks and lessen the negative effects of disrupted sleep patterns. Overall, exercise may help with melatonin production, which can help you sleep. There’s also some evidence that two compounds in your body — the hormone and neurotransmitter serotonin and neuropeptide Y — may play a part. Exercising tends to regulate their release, helping your body clock function properly.
But here’s where things get interesting. If you are experiencing sleep issues, exercise can have a significant circadian phase-shifting effect on your sleep and wake schedule. For instance, if you struggle to fall asleep at night, working out in the morning (or afternoon) can shift your circadian rhythms forward by signaling your body to produce your sleep hormone melatonin earlier in the evening. That could help you to fall asleep sooner.
If, on the other hand, you’re starting to work an overnight shift, an evening workout can help shift your body clock later for that delayed peak performance time frame.
The most important aspect of a sleep-friendly exercise routine? Consistency, says Dr. Chris Winter, sleep neurologist, Sleep Advisor to Sleep.com, and author of “The Sleep Solution.” Working out around the same time daily can help you establish a more predictable sleep-wake cycle, Winter says.
The zeitgeber: Temperature
How to work it: Cooler temperatures cool your body, which can reset your circadian rhythms by signaling and promoting sleep.
Programmed through our internal clocks, our body temperature tends to be higher during the day before gradually decreasing in the evenings. This drop coincides with the release of sleep hormone melatonin. “When you keep your home thermostat set at a consistent temperature, say 72 degrees, this signal may be lost, which can disrupt your sleep by not allowing your body temperature to drop at night,” Grant says.
Keeping your bedroom cool — 60 to 65 degrees — is optimal for good sleep. That might mean lowering the heat, opening a window, or turning on the air when it’s time for bed. You can also lower your nighttime body temperature by taking a warm/hot shower about an hour or two before bed.
“A hot shower or bath before bed may encourage sleep because it brings blood to the surface of the skin, which allows heat to radiate out,” says Grant. “That thermoregulation will cause a drop in your body temperature and signal your body to sleep.”
The zeitgeber: Social cues
How to work it: Maintain your social interactions at the same time every day
Social zeitgeber theory refers to the timing of our daily routines that act as zeitgebers by cueing our body clocks: getting out of bed, our first social interaction, the start of work or school, going to bed.
Major life events — divorce, job loss, or, you know, a 2-year global pandemic — are not just emotionally challenging, they can also disrupt our circadian clocks by causing changes to our daily routines: less regular bed-, wake- and meal-times, working all hours of the day (and night), regular social activities and interactions falling by the wayside. All these disrupted zeitgeber cues can have a circadian impact.
A set of regular daily routines can be therapeutic and help you’re your circadian rhythms aligned. “Especially during times of stress, creating stable routines that include your loved ones and colleagues adds an extra level of motivation and stability to your days, and nights,” says Grant. Because we are hardwired to be social creatures, we can be strongly motivated and modulated by doing our daily activities together with other people.
“So meet up with a friend to get your zeitgebers!” she says. “Think grabbing a morning coffee or taking a walk together at the same time each day – it can make winding your biological clocks more effective and more pleasant.” Putting it plainly, you can schedule your life to give yourself great sleep. “You can time your exercise, light exposure, food, and socializing to be consistent with the sleep wake schedule you want to have,” Grant explains.
Virtually all our biological processes are under direct or indirect control of the circadian system, and chronic disruption of circadian rhythms can lead to poor sleep and low daytime energy.
Signs of a sleep disorder can include:
- Having a hard time falling asleep
- Struggling to stay asleep, waking up frequently during the night
- Waking up too early and being unable to go back to sleep
- Not feeling rested after sleep, or your sleep is nonrestorative or of poor quality
- Becoming sleepy earlier in the evening than you’d like, or earlier than a conventional bedtime
- Problems with focus, memory, attention at work, in school or at home
What to take away about zeitgebers
“Routines create powerful anchors for the recurring internal mechanisms within our bodies,” says Grant. “If you’re having a hard time sleeping, or just want to dig into living as healthfully as possible, you have more control over your internal clock than you think, if you use your zeitgebers wisely!”
By making intentional choices about when you expose your body to light, when you eat, when you socialize, and when you exercise, you can help train your body to sleep at the optimal times for you.
If after making these changes, your sleep problems continue over several months, it’s a good idea to see a doctor to get an accurate diagnosis, and treatment.