Sleep cycles and gut health – the surprising link

sleep cycles

The National Sleep Foundation recommends that adults sleep between 7 to 9 hours every night. Whilst this might sound difficult to fit into our frantic 24/7 lives, sleeping is vital for our health, including our gut microbiome. 

Understanding how sleep cycles work

Sleep consists of two alternating phases: rapid eye movement (REM) sleep, characterised by fast, back and forth, left to right movements of the eyes, and non-REM sleep. 

Your sleep cycles start with non-REM sleep, which consists of four stages. With each stage, sleep becomes deeper and more restorative. In the final stages, hormones are released for growth and development, and tissue grows and repairs. 

About 90 minutes after falling asleep, you enter the first REM cycle. This is when we are most likely to dream, although the brain cycles back through the non-REM sleep stages after only 10 minutes in REM sleep. This cycle happens multiple times a night. 

The regulation of when we sleep or wake is determined by our circadian rhythm, a clever ‘biological clock’ managed by the suprachiasmatic (soo-pra-kai-as-MAT-ik) nucleus (SCN) of the hypothalamus, located in the brain. This responds to environmental factors like light exposure and temperature – we’re smarter than we think!

Our bodies also respond to the level of adenosine in our blood, a neurotransmitter which builds up during the day when we use energy. As this increases, we become drowsier, until finally we close our eyes. Once asleep, adenosine production decreases to a level that means our waking selves feel alert and ready to seize the day.

So why is sleep important?

Our bodies put in lots of effort to ensure we sleep – in fact we spend a third of our lives doing it!

Though we often neglect it (whether that’s staying up to watch a movie, or going out with friends), our bodies need sleep to function properly. From emotional regulation, to memory consolidation, to decreasing the risk of developing diabetes or heart disease, it’s clear that sleep is crucial for our overall well-being.  

How sleep impacts gut health

So how does this all link to gut health?

Disruption to circadian rhythms can alter the intestinal microbiota (microorganisms like bacteria), and this may have implications for inflammatory diseases. This is because changes to our microbiota can trigger inflammation, as well as increasing the permeability of the intestine wall, causing gut leakiness, which promotes inflammation. 

Consequently, disrupting our normal circadian rhythms – such as during jet lag or working night shifts – changes the intestinal microbiota community and makes the gut more susceptible to inflammation and dysbiosis, a term used to describe microbial imbalance, especially that of the gut. 

Dysbiosis is associated with illnesses such as inflammatory bowel disease (like Crohn’s disease and ulcerative colitis), irritable bowel syndrome (IBS), diabetes, obesity, and even depression. Indeed, sleep disruption is commonly experienced in patients suffering from inflammatory bowel disease. 

Tips for better sleep

Clearly, we need to start taking sleep more seriously. 

Though we often pay more attention to work and socialising than the quality of our sleep, your gut will thank you for a few extra hours of shut-eye, with increased sleep time positively correlating with gut microbiome diversity. The impacts of sleep deprivation can be severe for your gut microbiome (see our article: ‘How sleep deprivation affects your body’), so it’s worth prioritising your sleep cycles over finishing your favourite TV series! 

Here are some quick tips to help you drift off at night:

  1. Stick to a consistent sleep schedule 
  2. Limit blue light exposure from electronic devices
  3. Reduce your caffeine intake
  4. Avoid alcohol before bed
  5. Get 30 minutes of sunlight a day
  6. Exercise daily, but not within 2-3 hours of sleep

For more detailed advice on improving your sleep, why not take a look at our article ‘5 tips on how to get a better nights sleep’. Sweet dreams!

References

  1. Hirshkowitz M, Whiton K, Albert SM, et al. National Sleep Foundation’s sleep time duration recommendations: methodology and results summary. Sleep Health. 1(1):40-43. 2015. Available at: https://pubmed.ncbi.nlm.nih.gov/29073412/
  2. National Institute of Neurological Disorders and Stroke. Brain Basics: Understanding Sleep. Available at: https://www.ninds.nih.gov/Disorders/Patient-CaregiverEducation/Understanding-Sleep
  3. Sleep Foundation. What happens when you sleep. Available at: https://www.sleepfoundation.org/articles/what-happens-when-you-sleep
  4. Purves D, Augustine GJ, Fitzpatrick D, et al., ed. Stages of Sleep. Neuroscience. 2nd edition. Sunderland (MA): Sinauer Associates. 2001. Available from: https://www.ncbi.nlm.nih.gov/books/NBK10996/
  5. Carmona-Alcocer V, Abel JH, Sun TC, et al. Ontogeny of Circadian Rhythms and Synchrony in the Suprachiasmatic Nucleus. J Neurosci. 38(6):1326-1334. 2017. Available at: https://pubmed.ncbi.nlm.nih.gov/29054877/
  6. Matthew Walker. Why We Sleep: The New Science of Sleep and Dreams. Penguin Books Ltd. 2017. 
  7. Perry GS, Patil SP, Presley-Cantrell LR. Raising awareness of sleep as a healthy behavior. Prev Chronic Dis. 10:E133. 2013. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3741412/
  8. Voigt RM, Forsyth CB, Green SJ, Mutlu E, Engen P, Vitaterna MH, et al. Circadian Disorganization Alters Intestinal Microbiota. PLoS ONE 9(5): e97500. 2014. Available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0097500
  9. Summa KC, Voigt RM, Forsyth CB, Shaikh M, Cavanaugh K, et al. Disruption of the Circadian Clock in Mice Increases Intestinal Permeability and Promotes Alcohol-Induced Hepatic Pathology and Inflammation. PLoS One 8: e67102. 2013. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3688973/
  10. Forsyth CB, Voigt RM, Burgess HJ, Swanson GR, Keshavarzian A. Circadian rhythms, alcohol and gut interactions. Alcohol. 49(4):389-398. 2015. Available at: https://pubmed.ncbi.nlm.nih.gov/25499101/
  11. Biedermann L, Rogler G. The intestinal microbiota: its role in health and disease. Eur J Pediatr. 174(2):151-167. 2015. Available at: https://pubmed.ncbi.nlm.nih.gov/25563215/[1]Qazi T, Farraye FA. Sleep and Inflammatory Bowel Disease: An Important Bi-Directional Relationship. Inflamm Bowel Dis. 25(5):843-852. 2019. Available at: https://pubmed.ncbi.nlm.nih.gov/30388243/
  12. Qazi T, Farraye FA. Sleep and Inflammatory Bowel Disease: An Important Bi-Directional Relationship. Inflamm Bowel Dis. 25(5):843-852. 2019. Available at: https://pubmed.ncbi.nlm.nih.gov/30388243/
  13. Smith RP, Easson C, Lyle SM, Kapoor R, Donnelly CP, Davidson EJ, et al. (2019) Gut microbiome diversity is associated with sleep physiology in humans. PLoS ONE 14(10): e0222394.  Available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0222394