Have you ever noticed that you tend to get hungry or sleepy at pretty much the same time every day? Or perhaps you’re usually most alert when you first wake up—or later in the day? That’s your circadian rhythms at work.
These daily biological cycles influence almost all the body’s processes, and when they’re properly timed, they play a huge part in keeping you healthy physically, emotionally, and mentally. Here’s what you need to know about the way your body processes time, and how you can keep your internal clocks running without a hitch.
Understanding Circadian Rhythms
Circadian rhythms are the cyclical physical, mental, and behavioral changes you experience every day. These recurring cycles originate within the body, but are also strongly influenced by environmental factors—especially cycles of light and darkness. When these external influences are altered, this can reset, speed up, or slow down your circadian rhythms.
Almost all living things (like people, animals, plants, and even microbes!) have circadian rhythms. And these natural rhythms have an enormous effect on almost every aspect of your health as they govern your hormones, metabolism, sleep, blood pressure, digestive enzymes, brain chemicals, body temperature, coordination, muscle strength, cardiovascular efficiency, mood, and alertness throughout the day and night.1
While we all have circadian rhythms, our cycles aren’t necessarily on the same schedule—and whether you’re an early bird, a night owl, or something in-between, your chronotype is genetically determined. This genetic programming causes your body to be primed for peak performance (and for sleep) either earlier or later in the day. Most of us (about 60%) are in-betweeners, while the remaining 40% either have an early or late chronotype.
Interestingly, those with early chronotypes typically have an internal clock that’s slightly shorter than 24 hours—and the cycle of those with late chronotypes tends to run a bit longer—at about 25 hours. That’s not a problem though, because the light-dark cycle of day and night can easily reset our internal clocks every day to prevent us from getting out of synch.2
Circadian Rhythms vs. Biological Clocks
The terms circadian rhythms and biological clocks often get used interchangeably because they’re so closely related, but there’s an important technical distinction: Biological clocks are the actual internal timing mechanisms (causes) that create and regulate the measurable cycles of circadian rhythms (effects).
Biological clocks are made of special protein molecules that interact with your body’s cells—and the genes responsible for biological clocks exist in lots of different life forms including mammals, insects, and fungi.
Your body actually has multiple biological clocks that work in harmony to keep your circadian rhythms on track. The main one—your master clock—is located in your suprachiasmatic nucleus (or SCN) in the hypothalamus region of the brain, and it’s composed of about 20,000 nerve cells.
This master clock responds to the amount of light your eyes and optic nerves receive, and then goes on to manage a complex network of biological clocks that run throughout almost every organ in your body, turning on and off timekeeping proteins in a cycle that begins again about every 24 hours to correspond with the planet’s rotation.3
Your Gut Has a Rhythm Too!
With all wellness beginning in the gut, it’s exciting to discover that the microbiome seems to have its own internal clock and circadian rhythm, which also lines up with the planet’s rotation.
Recent research reveals that the numbers of certain types of gut bacteria, such as Bacteroidetes, Proteobacteria, and Verrucomicrobia, increase and decrease over a daily cycle. In simplest terms, the friendly microbes that feed on prebiotic fiber tend to grow at night when the food that was eaten during the day reaches the colon. Then during the daytime, these beneficial bacteria produce molecules that help them colonize effectively in the gut.4,5
What Happens If Our Clocks Get Out of Whack?
As long as our internal clocks are precisely tuned to the rising and setting of the sun, our circadian rhythms flow exactly as nature intended to keep us feeling great—no matter which chronotype we happen to have. The trouble is that these days, most of us don’t arrange our days according to the path of the sun. We often work all day in windowless offices, and then flood our homes with bright stimulating electric lighting in the evening.
The computers, smartphones, and TV’s we enjoy so much (often until bedtime) also signal our master clocks that we should stay alert as bedtime approaches. Late night snacking and meals work to further confuse your internal clocks—and when you throw shift work, exciting late night activities, and frequent travel across time zones into the mix, this only throws your body’s sense of time into deeper chaos.
When your body can’t tell what time it is (technically termed circadian disruption), this can lead to all kinds of unpleasant outcomes. At first you may just feel tired and cranky. But if the disruption continues a bit longer you might experience unwanted changes in metabolism, weight, mood, sleep, cognitive function, reaction time, and judgement.6,7 Ongoing, long-term circadian disruption becomes a true health concern that could lead to (or accelerate) serious cardiovascular, endocrine, cellular, and brain issues.8,9,10,11,12,13
One of the best things you can do to stay healthy is to keep your internal clocks properly tuned so your circadian rhythms flow smoothly—and you can do that by simply giving your biological clocks the love and respect they deserve.
Biological clocks thrive on stability, and they function best with predictable schedules of light, darkness, sleep, activity, and mealtimes that match the planet’s rotation. The bottom line is that in order to maintain the circadian rhythms you need to stay well, it’s essential to honor the cycle of the sun—with the understanding that your chronotype may call for you to set your schedule slightly earlier or later in the day.
If you’re not sure how to make that all work in the modern world, these simple tips will help get you started:
- Stick to a regular bedtime, and get up at about the same time every morning.
- Turn off screens at least an hour before bed—or better yet, right after dinner!
- Keep your bedroom as dark and cool as possible, and take all electronic devices out of your room before you go to sleep.
- Avoid bright home lighting in the evening—particularly short-wave, high-wattage blue light emitting bulbs, which are best suited for daytime hours. Instead, opt for longer-wave, low-wattage red, orange, or yellow bulbs (think candlelight hues) after sundown.
- Consider wearing blue light-blocking glasses if you must use screens in the evening.
- Make sure you’re exposed to lots of natural daylight (especially in the morning), either by spending time outdoors or near a sunny window. If you work in a windowless office, consider using a daylight spectrum lamp while you work.
- Know that consistently working during daylight hours and sleeping at night is your healthiest option, with the understanding that shift work is sometimes unavoidable.
- To keep your gut clock on schedule, limit eating to daylight hours, and fast for 12-14 hours once the sun sets. Supplementing with a high quality, time-released probiotic like PRO-15 and some organic prebiotic powder will further support your healthy gut rhythms.
- If you travel across time zones, try an app like Timeshifter to help reset your internal clocks to your new location quickly and smoothly.
When your body knows what time it is, everything else just seems to fall into place. And the best news of the day is that the key to resetting and maintaining your internal clocks is as simple and joyful as following the sun.
1.Circadian rhythms. (n.d.). NIGMS National Institute of General Medical Sciences. https://www.nigms.nih.gov/education/fact-sheets/Pages/circadian-rhythms.aspx
2. Curtis, B. J., Ashbrook, L. H., Young, T., Finn, L. A., Fu, Y., Ptáček, L. J., & Jones, C. R. (2019). Extreme morning chronotypes are often familial and not exceedingly rare: The estimated prevalence of advanced sleep phase, familial advanced sleep phase, and advanced sleep–wake phase disorder in a sleep clinic population. Sleep, 42(10).
3. The Nobel prize in physiology or medicine 2017. (n.d.). NobelPrize.org. https://www.nobelprize.org/prizes/medicine/2017/press-release/
4. Teichman, E. M., O’Riordan, K. J., Gahan, C. G., Dinan, T. G., & Cryan, J. F. (2020). When rhythms meet the blues: Circadian interactions with the microbiota-gut-Brain Axis. Cell Metabolism, 31(3), 448-471.
5. Parkar, S., Kalsbeek, A., & Cheeseman, J. (2019). Potential role for the gut microbiota in modulating host circadian rhythms and metabolic health. Microorganisms, 7(2), 41.
6. McClung, C. A. (2013). How might circadian rhythms control mood? Let me count the ways... Biological Psychiatry, 74(4), 242-249.
7. Potter, G. D., Skene, D. J., Arendt, J., Cade, J. E., Grant, P. J., & Hardie, L. J. (2016). Circadian rhythm and sleep disruption: Causes, metabolic consequences, and countermeasures. Endocrine Reviews, 37(6), 584-608.
8. Brainard, J., Gobel, M., Scott, B., Koeppen, M., & Eckle, T. (2015). Health implications of disrupted circadian rhythms and the potential for daylight as therapy. Anesthesiology, 122(5), 1170-1175.
9. Gale, J. E., Cox, H. I., Qian, J., Block, G. D., Colwell, C. S., & Matveyenko, A. V. (2011). Disruption of circadian rhythms accelerates development of diabetes through pancreatic beta-cell loss and dysfunction. Journal of Biological Rhythms, 26(5), 423-433.
10. Musiek, E. S., Xiong, D. D., & Holtzman, D. M. (2015). Sleep, circadian rhythms, and the pathogenesis of Alzheimer disease. Experimental & Molecular Medicine, 47(3), e148-e148.
11. Salavaty, A. (2015). Carcinogenic effects of circadian disruption: An epigenetic viewpoint. Chinese Journal of Cancer, 34(3).
12. Videnovic, A. (2015). Dysregulation of circadian system in Parkinson’s disease. Disorders of Sleep and Circadian Rhythms in Parkinson's Disease, 117-129.
13. Zhang, Y., & Papantoniou, K. (2019). Night shift work and its carcinogenicity. The Lancet Oncology, 20(10), e550.
Roberta Pescow is a writer at Hyperbiotics and proud mom of two amazing and unique young men. Natural wellness is a subject she’s passionate about, so she loves sharing information that helps others discover all the ways probiotics support glowing health and well-being. To learn more about how a healthy microbiome can enrich your life, subscribe to our newsletter.