Struggling to maintain a regular sleep cycle? Did you know the answer could lie in your gut?

It is home to trillions of bacteria and is a self-contained nervous system of 200-600 million neurons1. Its complexity and influence leads some to call the gut the ‘second brain’.

To understand the gut’s importance, it’s crucial to understand that it’s not one singular system, but a complex ecosystem comprised of approximately 150 times2 more genetic information than is found in the rest of the human genome. 

As the world continually looks for ways to de-stress and maintain regular rest patterns, one of the most interesting avenues of exploration is how the gut can affect sleep. The key lies in the gut-brain axis; core pathways of communication between the gut and the brain that include the vagus nerve, the neuroendocrine pathway, including the HPA axis, and the immunoregulatory pathway. These channels of communication are thought to be responsible for a broad range of bodily processes and behaviours, one of which is sleep pattern.

Sleep is absolutely essential to the body and its complex processes. Irregular sleep-wake cycles, alongside insomnia, are a known comorbidity of several affective disorders. The quality of sleep has been linked to anxiety and depression, demonstrating the profound importance of a reliable rest cycle.

There are several ways in which gut health and sleep are thought to be interlinked:

Healthy gut, healthy mind

A study in 20173 showed a possible connection between the gut microbiota, sleep health and cognitive flexibility in a control group of adults aged between 50 and 85. The study included the Pittsburgh Sleep Quality Index and Stroop Color Word Test as metrics, and the result indicated a relationship between sleep quality and microbial diversity in the gut. The study suggests that the trillions of bacteria in the gut microbiome could directly affect the brain’s function, which in turn is largely responsible for sleep patterns and effective rest.

This points to an interesting crossover between the fields of gastroenterology and neuroscience; a dynamic that has been explored in the first phase of the Human Microbiome Project, which seeks to outline the full extent of the gut’s influence over the body. 

Two key factors are at play in this relationship. It is understood that the gut microbiome can affect mental cognition via the gut-brain axis, including moderation of mood and stress levels. Neuroscience also understands a significant link between mood and sleep patterns, where heightened emotional or psychological stress can disrupt sleep and cause sleep deprivation or insomnia. Research into the full extent of the relationship is ongoing, revealing that gut health could have a very close relationship to sleep quality and maintaining a healthy circadian rhythm. 

Circadian Rhythm

Closely linked to the gut-brain axis, Circadian Rhythm is the internal ‘body clock’ that regulates the expenditure of energy, appetite and sleep. It is purported in a 2019 report from the University of Auckland4 that there may be a significant and direct link between gut microbiota and the host circadian rhythm, as well as metabolic health. 

The link appears to be an increase in Firmicutes, a specific class of bacteria usually found in the gut. Some bacteria in the Firmicutes grouphave been observed to flourish during morning feeding periods and decrease over time through the day, which could contribute to how the body maintains an internal clock. The same research suggests that prebiotics, a type of dietary fibre, could be an effective method of tackling gut microbial dysbiosis, while having a positive impact on sleep. The study indicates opportunity to use prebiotics to positively impact the growth of beneficial endogenous organisms to support sleep regularity and overall health.


Part of what dictates our sleep patterns is the release of chemicals. The intestine produces and releases many of the same neurotransmitters as the brain, including dopamine and serotonin – both of which are important chemicals for sleeping. Serotonin for example, has been shown to play an important role in sleep, directly stimulating the enteric neurons that cause sleep. 

Melatoninis a hormone produced by the pineal gland, which is largely responsible for managing the natural circadian rhythm of the body. Studies show that if the pineal gland is compromised, or not functioning effectively, tryptophan in the gut can be converted into melatonin to regulate the sleep-wake cycle in its place.

The composition of bacteria in the gut can directly influence the release of these neurotransmitters, including serotonin, GABA and tryptophan, which further indicates that a balanced gut could hold the key to a restful night’s sleep. The fact that the intestine is also capable of producing and releasing these neurotransmitters speaks to the gut’s reputation as the ‘second brain’. 

Poor sleep could affect your gut microbiome

The connection between brain and gut health also works the other way round, where poor sleep patterns have a detrimental effect on gut health, hinting at the complexity of the relationship. A 2016 study in Molecular Metabolism5 showed that disrupted sleep patterns can impact the balance of the gut microbiome and the known benefits that come with a diverse bacterial profile. 

The study showed that short term sleep loss affected certain pathogenic bacterial strains, which as a consequence, became more abundant and decreased the level of several types of beneficial bacteria. 

In summary

A significant amount of research highlights that the gut plays a significant role in modulating sleep patterns. Gut health appears to play an important role in overall wellbeing and, excitingly, we are only now uncovering the true extent.

The gut-brain axis is central to the complex relationship between gut health and regular sleep rhythm. By maintaining a balanced and thriving gut microbiome, we allow the gut to function at its best and take advantage of the bidirectional signals at play. 

Looking to support a strong circadian rhythm and consistent rest pattern? The gut microbiome could hold the key to success to a good night’s rest!


1 Furness et al. 2014; The enteric nervous system and gastrointestinal innervation: integrated local and central control. Adv Exp Med Biol. 2014;817:39-71. doi: 10.1007/978-1-4939-0897-4_3. https://www.ncbi.nlm.nih.gov/pubmed/24997029

2 Diaz Heijtz R and Swann J, 2019, Current Opinion in Pharmacology, 48:xx–yy https://doi.org/10.1016/j.coph.2019.09.002

3 Anderson et al., 2017; A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adults. Sleep Medicine https://www.sciencedirect.com/science/article/abs/pii/S1389945717303179

4 Parkar, Kalsbeek and Cheeseman 2019, Potential Role for the Gut Microbiota in Modulating Host Circadian Rhythms and Metabolic Health, Univeristy of Auckland https://www.mdpi.com/2076-2607/7/2/41/htm5 Benedict et al., 2016, Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals, Molecular Metabolism https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123208/

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