A study from Peking University reveals that the balance of the intestinal microbiota influences sleep quality and associated disorders.
MADRID, November 4 (EUROPAPRESS).- What if the secret to sleep deeply was not in one tabletnor in the meditationbut in your own intestine? More and more studies indicate that bacteria that live in our body They could have a lot to say about how we sleep. a new investigation goes one step further and reveals that the balance – or chaos – of your microbiota could be marking your sleepless nights.
The intestine, that “second brain” that also controls sleep
The microbiota-gut-brain axis is a fundamental pathway to understanding and potentially treating sleep disorders, according to experts from the Peking University (China). Specifically, as stated in an exhaustive review published in Brain Medicinethe teacher Lin Lu of the Sixth Hospital from Peking University and an international team of collaborators from institutions in China and the United States, has managed to synthesize current knowledge about how the trillions of bacteria that reside in our digestive system directly and indirectly influence our sleep-wake cycles.
The research team examined evidence from clinical studies in humans and animal models, revealing consistent patterns of microbial dysbiosis – an imbalance in gut bacterial communities – in people with sleep disorders. In particular, patients with chronic insomnia show reduced microbial diversity and altered abundance of specific bacterial families compared to healthy controls.
Similar patterns are seen in obstructive sleep apnea, where reduced levels of beneficial bacteria correlate with the severity of the disease.
Recent advances in microbiome research have transcended simple correlational studies to give way to hypothesis-driven research that reveals connections at the molecular level between the microbiome and sleep disorders. These advances are essential to understand how the microbiota influences sleep and to develop specific therapies to effectively treat sleep disorders.
Metabolites that help (or harm) your hours of sleep
This review also identifies various biological pathways through which the intestinal microbiota influences sleep regulation, creating a complex network of metabolic, neurological and immunological interactions. Microbial metabolites play a critical role; Short-chain fatty acids, such as butyrate, have shown protective effects against sleep disturbance in multiple studies.
These compounds, produced through bacterial fermentation of dietary fiber, can modulate inflammation, strengthen intestinal barriers, and influence neurotransmitter systems essential for sleep. Clinical trials have shown that sodium butyrate supplementation improves sleep quality in patients with active ulcerative colitis, while animal studies demonstrate that butyrate attenuates inflammatory responses and memory impairment induced by sleep deprivation.
Bile acids represent another important class of microbial metabolites that affect sleep. Research reveals that chronic insomnia is associated with elevated levels of primary bile acids, such asmuracholic acid and norcolic acid, along with a reduction in secondary bile acids, such as isolithocholic acid, lithocholic acid, and ursodeoxycholic acid.
This pattern correlates with specific populations of gut bacteria, particularly lower abundance of Ruminococcaceae species, and may contribute to the risk of cardiometabolic diseases in sleep-deprived people. These findings suggest that the microbiota-bile acid axis plays a critical role in the impact of chronic insomnia on cardiovascular and metabolic health.
The microbiota also influences the production of neurotransmitters directly involved in sleep regulation. Certain gut bacteria, including strains of Lactobacillus and Bidobacterium, possess genes that encode glutamate decarboxylase, which facilitates the production of gamma-aminobutyric acid (GABA), a primary inhibitory neurotransmitter that promotes sleep.
Electroencephalography studies have shown that oral ingestion of GABA induces changes in brain responses, indicating that GABA produced or supplemented through the intestine can influence central nervous system activity and sleep architecture.
Furthermore, more than ninety percent of the body’s serotonin is synthesized in the intestine, with intestinal bacteria being the main producers, especially in the neonatal intestine.
Serotonin concentrations fluctuate rhythmically during the sleep-wake cycle, reaching their peak during wakefulness and their lowest levels during REM sleep. Sleep-deprived mice present alterations in the metabolism of tryptophan – a precursor of both serotonin and melatonin -, changes that depend on the microbiome and are located in the intestine.
The gastrointestinal tract is also the most important extrapineal source of melatonin, with concentrations up to four hundred times higher than those found in plasma, underscoring the crucial role of the intestine in regulating circadian rhythms and sleep.
When the microbiota becomes unbalanced
Furthermore, this review systematically examines microbial alterations in major sleep disorders, revealing both disorder-specific changes and convergent patterns. In insomnia, the most prevalent sleep disorder, studies with thousands of participants reveal consistent decreases in beneficial bacterial genera, along with changes in metabolite profiles. A pivotal study with 6,398 participants found significant differences in microbial beta diversity between patients with chronic insomnia and healthy individuals, with chronic insomnia being associated with lower levels of specific Ruminococcaceae species.
These bacterial changes mediated the inverse association between chronic insomnia and cardiometabolic diseases through alterations in bile acids.
The review highlights that sleep disorders often accompany neuropsychiatric conditions such as depression, anxiety disorders, autism spectrum disorder, and neurodegenerative diseases. In these cases, alterations in the gut microbiota may contribute to both the primary psychiatric condition and comorbid sleep problems through shared inflammatory and neurotransmission pathways. For example, certain bacterial genera, such as Blautia, Coprococcus, and Dorea, correlate with indicators of sleep quality in patients with major depressive disorder, while Intestinibacter shows associations with both sleep quality and insomnia severity.
New approach to treating insomnia from the gut
Thus, this exhaustive peer-reviewed article establishes the microbiota-gut-brain axis as a critical, although underappreciated, factor in sleep regulation, synthesizing evidence from various sleep disorders and neuropsychiatric conditions.
Converging evidence from correlational studies, mechanistic investigations, and therapeutic interventions indicates that gut microbiota dysbiosis causes and, in turn, contributes to sleep disorders, creating potential vicious cycles that perpetuate poor sleep quality and associated health problems.
The identification of convergent alterations in multiple sleep disorders, including increased ratios of Firmicutes/Bacteroidetes, elevated levels of Actinobacteria and Collinsella, along with decreased abundance of beneficial genera such as Bacteroides, Bidobacterium, and Faecalibacterium, suggests that these changes may represent common microbial bases or consequences of disturbed sleep, potentially contributing to the systemic inflammation and metabolic dysregulation frequently observed in patients with sleep disorders.
As research continues to elucidate these complex interactions, interventions targeting the microbiota represent a promising avenue to address the global burden of sleep disorders, while also offering potential benefits for overall brain health, metabolic function, and quality of life.
The evidence presented in this review provides a solid basis for the development of precision probiotics, optimized prebiotics and personalized synbiotic formulations, tailored to specific sleep disorders and the individual characteristics of each patient.