Written by Sophie Medlin
Did you know that your gut and your gut bacteria follow your body clock or circadian rhythm just like the rest of your body? That’s why some of us always need a poo when we wake up. Our gut goes to sleep overnight and wakes up when the sunrises. That’s also why it can be tricky to sleep when you’ve had a big meal before bed, because your gut has to keep working on it, not allowing your body to fully switch off for sleep.
Not only does our bowel as an organ go to sleep when we do but research has also revealed  that our colonic microbiome follows our circadian rhythm too! The biggest populations of bacteria in our microbiome fluctuate in their numbers between night and day. This isn’t just because we feed them in the day and not at night, they also seem to respond to our internal body clock. These are normal day-to-night fluctuations that don’t have a significant impact on our health.
When we mess around with our body clock however, through shift work, pulling regular all-nighters and travelling to different time zones, our gut bacteria is impacted in the longer term. Research has shown that Chronic sleep disturbance triggers changes in our gut bacteria , reducing the total number or organisms in the lactobacillacea family (the good guys) and increasing other populations leading to dysbiosis.
As is so often the case, we have a chicken or egg scenario here because we also know that those who suffer with insomnia also have a different microbiome pattern to those who sleep well . The researchers found that these changes were so strongly indicative of insomnia that they proposed to use the microbiome as a means to diagnose insomnia disorders. So did the sleep change cause the shift in the microbiome or is it our microbiome affecting our sleep?
Well, it has been shown that gut bacteria have a role to play in serotonin production and metabolism  which is very important for REM sleep where we are able to process emotions and support our brain health. This can mean that the less sleep, we get, the greater the changes to our microbiome, leading to longer term problems with sleep quality. Perhaps this helps to explain how sleep problems become chronic with time.
Another affect of lack of sleep is on our appetite. Research has shown that sleep deprived people consume around 400 calories more per day in comparison to when they’re not sleep deprived. Research also suggests  that this might be contributed to by our microbiome through changes to bacterial species leading to a reducing in butyrate which is linked with appetite regulation. Poor sleep and weight gain can be closely linked so this is another great reason to look after your microbiome.
The good news is that a diet rich in prebiotic fibre may well help us to sleep better. A 2020 study  showed that when rats are fed a diet rich in prebiotic fibre, they gain a whole host of benefits from their microbiome, including increases in metabolites and hormones that support better sleep.
Research has also shown that diversity of species in the microbiome is important for sleep . While some people might take that as a sign to reach for probiotic supplements, fermented food and eating plenty of plants is the best place to start when trying to improve your microbiome diversity.
As always with our microbiome, sleep and gut bacteria have a bi-directional relationship where what we do affects our gut bacteria and what they do affects us. Which ever way you look at it, this is just another really great reason to invest in your gut health and low after your microbial friends.
- 1.Parker, Kalsbeek and Cheeseman 2019 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6406615/
- 2. Parker, Kalsbeek and Cheeseman 2019 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6406615/
- 3. Liu et al 2019 – https://www.frontiersin.org/articles/10.3389/fmicb.2019.01770/full
- 4. Li, Hao, Fan and Zhang 2018 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6290721/
- 5. Parker, Kalsbeek and Cheeseman 2019 – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6406615/
- 6. Thompson et al 2020 – https://www.nature.com/articles/s41598-020-60679-y
- 7. Hagen et al 2019 – https://doi.org/10.1093/sleep/zsz067.105
About the author
Sophie Medlin, founder of City Dietitians, is a well-recognised consultant dietitian and is the Chair for the British Dietetic Association for London. She has expertise in gastrointestinal and colorectal health and has worked in acute hospitals specialising in gastrointestinal diseases before moving into academia. Sophie has specialist knowledge and skills in the management of medical conditions such as irritable bowel syndrome (IBS), colorectal dysfunction, diverticular disease and polycystic ovarian syndrome.