A huge amount of information travels along the nerves that supply the gut, both from the brain to the gut and from the gut to the brain. There is so much nerve activity in the gut that it has sometimes been called our “second brain”.1-4 These connections between the gut and the brain influence so many aspects of our life: hunger levels,5 mood,6,7 how well we digest our food, how food moves through the gut8 and sleep.9 If you doubt the strength of these connections, think how stage-fright can make a person feel sick!
Sleep and the gut
It’s been known for years that not getting enough sleep can increase hunger levels and lead to obesity.5 Interestingly, our gut bacteria are affected by our body rhythms of sleep and wakefulness.9 This change can happen very quickly: studies of jet lag show changes in the balance of the gut bacteria, which reverse when the person is no longer jet-lagged.10,11 In an experiment where animals had their sleep deliberately disrupted, within a week their gut bacteria took a turn for the worse – favouring bacteria that are linked with inflammation (and at the same time their blood pressure increased).12 It even seems that our gut bacteria may be able to influence our genes that control these rhythms!13 Thus, the composition and characteristics of our gut bacteria are linked to our sleep patterns.
We know that our gut bacteria can communicate with the brain because they can influence the manufacture of several chemicals that our bodies use to send signals along our nerves, including serotonin and dopamine.14 This is important because serotonin and dopamine are key players in our moods.15 And, from the point of view of affecting sleep, serotonin is used by the body to make melatonin (aka the sleep hormone). Around 90% of the serotonin in our bodies is produced in the gut so the health of our gut is clearly going to be relevant to how well we make melatonin and hence our ability to sleep well.
On the downside, if we have an imbalance in our gut bacteria, the less helpful bacteria can make chemicals that can contribute to insomnia, such as ammonia and lactic acid.15,17
Changing the gut bacteria can improve sleep
Problems with insomnia often go alongside gut issues. People with irritable bowel syndrome (IBS) are more likely to have sleep issues than those without.18 Measures to improve the balance of the gut bacteria have been shown to improve sleep.9 For example, certain prebiotic fibres that specifically provide food for bacteria that promote serotonin can improve sleep quality.19,20
Can better sleep translate to better gut health?
Of course, getting a good night’s sleep depends on other factors than simply feeding the right gut bacteria. Most important is the timing of our exposure to light and dark.21 Changes have been seen in numbers of certain gut bacteria that correspond to our light and dark cycles.11 As noted above, recovery from jet-lag and stopping disrupting the sleep of the experimental rats resulted in changes in the gut microbiome for the better.
Get a better night’s sleep
If you experience disrupted sleep, have trouble getting off to sleep or wake up very early in the morning, or regularly get less than 6 hours of sleep, read our article on how to improve your sleep here.
- Dinan TG, Cryan JF. Gut-brain axis in 2016: Brain-gut-microbiota axis-mood, metabolism and behaviour. Nature Reviews Gastroenterology and Hepatology. 2017;14(2):69-70. doi:10.1038/nrgastro.2016.200
- Clapp M, Aurora N, Herrera L, Bhatia M, Wilen E, Wakefield S. Gut microbiota’s effect on mental health: The gut-brain axis. Clinics and practice. 2017;7(4):987. doi:10.4081/cp.2017.987
- Sherwin E, Rea K, Dinan TG, Cryan JF. A gut (microbiome) feeling about the brain. Current Opinion in Gastroenterology. 2016;32(2):96-102. doi:10.1097/MOG.0000000000000244
- Smith PA. The tantalizing links between gut microbes and the brain. Nature. 2015;526(7573):312-314. doi:10.1038/526312a
- Agustí A, García-Pardo MP, López-Almela I, et al. Interplay between the gut-brain axis, obesity and cognitive function. Frontiers in Neuroscience. 2018;12(MAR). doi:10.3389/fnins.2018.00155
- Rogers GB, Keating DJ, Young RL, Wong ML, Licinio J, Wesselingh S. From gut dysbiosis to altered brain function and mental illness: Mechanisms and pathways. Molecular Psychiatry. 2016;21(6):738-748. doi:10.1038/mp.2016.50
- Evrensel A, Ceylan ME. The gut-brain axis: the missing link in depression. Clinical psychopharmacology and neuroscience : the official scientific journal of the Korean College of Neuropsychopharmacology. 2015;13(3):239-244. doi:10.9758/cpn.2015.13.3.239
- Mayer EA, Savidge T, Shulman RJ. Brain-gut microbiome interactions and functional bowel disorders. Gastroenterology. 2014;146(6):1500-1512. doi:10.1053/j.gastro.2014.02.037
- Matenchuk BA, Mandhane PJ, Kozyrskyj AL. Sleep, circadian rhythm, and gut microbiota. Sleep Medicine Reviews. 2020;53. doi:10.1016/j.smrv.2020.101340
- Li Y, Hao Y, Fan F, Zhang B. The Role of Microbiome in Insomnia, Circadian Disturbance and Depression. Frontiers in Psychiatry. 2018;9:669. doi:10.3389/fpsyt.2018.00669
- Liu Z, Wei Z-Y, Chen J, et al. Acute sleep-wake cycle shift results in community alteration of human gut microbiome. mSphere. 2020;5(1). doi:10.1128/msphere.00914-19
- Parkar SG, Kalsbeek A, Cheeseman JF. Potential role for the gut microbiota in modulating host circadian rhythms and metabolic health. Microorganisms. 2019;7(2). doi:10.3390/microorganisms7020041
- Mashaqi S, Gozal D. Circadian misalignment and the gut microbiome. A bidirectional relationship triggering inflammation and metabolic disorders - a literature review. Sleep Medicine. 2020;72:93-108. doi:10.1016/j.sleep.2020.03.020
- Yano JM, Yu K, Donaldson GP, et al. Indigenous bacteria from the gut microbiota regulate host serotonin biosynthesis. Cell. 2015;161(2):264. doi:10.1016/j.cell.2015.02.047
- Valles-Colomer M, Falony G, Darzi Y, et al. The neuroactive potential of the human gut microbiota in quality of life and depression. Nature Microbiology. 2019;4(4):623-632. doi:10.1038/s41564-018-0337-x
- Saji N, Murotani K, Hisada T, et al. Relationship between dementia and gut microbiome-associated metabolites: a cross-sectional study in Japan. Scientific Reports. 2020;10(8088). doi:https://doi.org/10.1038/s41598-020-65196-6
- Galland L. The gut microbiome and the brain. Journal of Medicinal Food. 2014;17(12):1261-1272. doi:10.1089/jmf.2014.7000
- Wang B, Duan R, Duan L. Prevalence of sleep disorder in irritable bowel syndrome: A systematic review with meta-analysis. Saudi Journal of Gastroenterology. 2018;24(3):141-150. doi:10.4103/sjg.SJG_603_17
- Thompson R, Roller R, Mika A, et al. a prebiotic blend of polydextrose and galactooligosaccharides with bioactive whey protein fractions ameliorates stress-evoked disruptions in sleep states. The FASEB Journal. Published online 2015.
- Thompson RS, Roller R, Mika A, et al. Dietary prebiotics and bioactive milk fractions improve NREM sleep, enhance REM sleep rebound and attenuate the stress-induced decrease in diurnal temperature and gut microbial alpha diversity. Frontiers in Behavioral Neuroscience. 2017;10. doi:10.3389/fnbeh.2016.00240
- Harb F, Hidalgo MP, Martau B. Lack of exposure to natural light in the workspace is associated with physiological, sleep and depressive symptoms. Chronobiology International. 2015;32(3):368-375. doi:10.3109/07420528.2014.982757