Sleep and the gut microbiome

You might be curious to understand how the bacteria in the gut can affect sleep. The gut microbiome is home to around 5000 species of bacteria, and collectively they are responsible for supporting homeostatic functions in the body (Afzaal et al., 2022). Sleep is a crucial part of human life to restore energy and healthy adults require at least 7 hours of good quality sleep (Suni., 2021). The gut and sleep are more closely interlinked than it may appear, and one of the important links to this relationship is the gut-brain axis.

Here's how...

The gut-brain axis

The gut-brain axis is the bidirectional communication between the enteric and central nervous systems and is important for regulating some homeostatic and physiological processes in the human body (Appleton., 2018). This can be achieved by crosstalk between the gut and the brain via secondary metabolites, such as short-chain fatty acids, produced by beneficial bacteria (Mayer et al., 2022). Importantly, the gut-brain axis has been shown to support cognitive function and sleep via the production of neurotransmitters and hormones, such as serotonin and melatonin, which largely occur in the gut and travel via signals to the brain, to support relaxation and prolong sleep duration (Sen et al., 2021).

Key hormones for sleep regulation

There are key hormones that regulate the sleep-wake cycle, two of which are serotonin and melatonin.

Serotonin

Serotonin is a neurotransmitter produced by gut bacteria and is an important player in the sleep-wake cycle by promoting relaxation, controlling the quality of sleep and switching between rapid-eye movement (REM) sleep and non-REM sleep (Brown et al., 2012).

Melatonin

Melatonin, known as the ‘darkness hormone’, is produced in the pineal gland in the brain and is released periodically throughout the day and night to support the sleep-wake cycle. Whilst the pineal gland is mainly responsible for melatonin production, bacteria in the gut can also produce melatonin from tryptophan, and this can have a benefit for sleep (Ahmadi et al., 2024)

What are the benefits of sleep on the gut microbiome?

In a study conducted by Smith et al (2019), they investigated whether sleep has a positive correlation with the gut microbiome – which they found was correct - as they measured the length and quality of sleep with the bacteria present in the gut. From this study, Smith et al (2019) found that a higher bacterial diversity is positively correlated with sleep time and efficiency. Similar findings were discovered by, Anderson et al (2017) who identified that specific strains of bacteria, such as those belonging to the Verrucimicrobia and Lentisphaerar phyla were positively associated with quality of sleep compared to Selenomonadales and Negativicutes,which were negatively associated with sleep quality, identified by Newsom (2023).

The relationship between the gut microbiota and sleep could also have further implications for health that extend beyond sleep quality and duration. In 2022, Tsereteli and co looked into the effects of sleep on blood glucose control. The study showed that when individuals had poor sleep, they had poorer post-prandial blood glucose control and altered glucose metabolism, suggesting that individuals may be more likely to opt for less nutrient dense food choices following a poor night’s sleep (Tsereteli et al., 2022). Given that poor sleep can have a big impact on other areas of wellbeing, including nutrition, identifying strategies for improving sleep is important to ensure that balance can be achieved in other areas of health.

The Takeaway

So, when you hear phrases such as ‘trust your gut’, it could have a deeper meaning. Research has shown that there is a strong link between the brain and the gut which can have far-reaching impacts on different areas of well-being, including sleep. From the current research on the gut microbiome, there is extensive information regarding the gut-brain axis, but when it comes to specificities such as sleep, this is an area that needs to be researched in more detail to gain a better understanding of the role and potential of the gut microbiome.

By Libby Redmile, 2^ndYear BSc Food Science and Nutrition student at Northumbria University

Completed as part of a work experience placement programme at Clasado.

References

Afzaal, M., Saeed, F., Shah, Y.A., Hussain, M., Rabail, R., Socol, C.T., Hassoun, A., Pateiro, M., Lorenzo, J.M., Rusu, A.V. and Aadil, R.M. (2022). Human gut microbiota in health and disease: Unveiling the relationship. Frontiers in Microbiology, 13.

Ahmadi, S., et al. (2024). ‘Gut microbiota in neurological diseases: Melatonin plays an important regulatory role.’ Biomed Pharmacotherapy 174: 116487.

Anderson, J. R., et al. (2017). ‘A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adults.’ Sleep Med 38: 104-107.

Appleton, J. (2018). ‘The Gut-Brain Axis: Influence of Microbiota on Mood and Mental Health.’ Integ Med (Encinitas) 17(4): 28-32.

Brown, R. E., et al. (2012). ‘Control of sleep and wakefulness.’ Physiol Rev 92(3): 1087-1187.

Carabotti, M., et al. (2015). ‘The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.’ Ann Gastroenterol 28(2): 203-209.

Mayer, E.A., Nance, K. and Chen, S. (2022). The Gut–Brain Axis. Annual Review of Medicine, [online] 73(1), pp.439–453. Available at: https://www.annualreviews.org/content/journals/10.1146/annurev-med-042320-014032.

Newsom, R. (2023, 20 October, 2023). ‘New Study Shows What’s in Your Gut Influences How and When You Sleep.’ Retrieved 7th May, 2024, from https://www.sleepfoundation.org/sleep-news/gut-microbiome-affects-sleep#:~:text=The%20study%20found%20that%20the,that%20the%20amount%20of%20fiber.

Sen, P., Molinero-Perez, A., O’Riordan, K.J., McCafferty, C.P., O’Halloran, K.D. and Cryan, J.F. (2021). Microbiota and sleep: awakening the gut feeling. Trends in Molecular Medicine, [online] 27(10), pp.935–945. Available at: https://www.sciencedirect.com/science/article/pii/S1471491421001854?casa_token=qQqAMMEMkm0AAAAA:Yk4Dy55lxnjn2RqMMjZDMmxmvIpJoDBpXfb1UbtIuL-q22LZ3wY9T77P9tjy2YcZ9134rbKnmg.

Smith, R. P., et al. (2019). ‘Gut microbiome diversity is associated with sleep physiology in humans.’ PLoS One 14(10): e0222394.

Suni, E. (2021). How Much Sleep Do We Really Need? [online] Sleep Foundation. Available at: https://www.sleepfoundation.org/how-sleep-works/how-much-sleep-do-we-really-need.

Tsereteli, N., et al. (2022). ‘Impact of insufficient sleep on dysregulated blood glucose control under standardised meal conditions.’ Diabetologia 65(2): 356-365.