Many people believe that good sleep begins in the brain, but restful sleep actually starts lower in the body—specifically in the gut, according to Science Alert.
اضافة اعلان
The community of trillions of microbes living in the digestive system, known as the gut microbiome, plays a major role in regulating sleep quality, mood, and overall health.
When the gut microbiome is balanced and healthy, sleep tends to improve. When it is disrupted, insomnia, sleep disturbances, and poor sleep cycles often appear.
The Vagus Nerve
The gut and the brain are in constant communication through a single axis that includes nerves, hormones, and immune signals. The most well-known component of this system is the vagus nerve, which acts as a two-way communication line carrying information between the gut and the brain.
Researchers are still studying how important the vagus nerve is for sleep, but evidence suggests that increased vagal activity supports a calm nervous system, steady heart rate, and smoother transitions into rest. Because of this close relationship, changes in the gut affect how the brain regulates stress, mood, and sleep.
How the Gut Sends Signals to the Brain
Dr. Manal Mohammed, Senior Lecturer in Medical Microbiology at the University of Westminster, explains that gut microbes not only help digest food but also produce neurotransmitters and metabolites that influence sleep-related hormones. Metabolites are small chemical byproducts formed when microbes break down food or interact with one another.
Many of these compounds can affect inflammation, hormone production, and the body’s internal clock.
Microbial Imbalance
When the gut is balanced, these substances send calm, steady signals that support regular sleep. When the microbiome is disrupted—a condition known as dysbiosis—this communication system becomes unreliable.
Serotonin and Melatonin
The gut also produces many key chemicals linked to sleep. For example, serotonin regulates mood and helps control the sleep–wake cycle. Most of the body’s serotonin is produced in the gut, and beneficial bacteria help keep its production stable.
Melatonin, which signals the body to feel sleepy at night, is produced in the pineal gland as well as throughout the digestive system. The gut helps convert serotonin into melatonin, meaning gut health directly affects how efficiently this process occurs.
Gamma-Aminobutyric Acid (GABA)
The gut also supports the production of gamma-aminobutyric acid (GABA), a calming neurotransmitter produced by certain beneficial microbes. GABA soothes the nervous system and signals that the body is safe enough to relax.
Together, these chemicals form part of the body’s circadian rhythm—the 24-hour internal cycle that regulates sleep, appetite, hormones, and body temperature.
Harmful Bacteria and Inflammation
When harmful bacteria dominate, this rhythm becomes less stable, contributing to insomnia, pre-sleep anxiety, and fragmented sleep.
Inflammation is another major factor linking the gut to sleep. A healthy digestive system maintains a balanced immune response by protecting the gut lining and hosting microbes that regulate immune activity and produce anti-inflammatory compounds.
If the microbiome becomes imbalanced or the gut lining is irritated due to poor nutrition, gaps can form between intestinal cells. This allows inflammatory molecules to leak into the bloodstream, causing chronic low-grade inflammation.
Inflammation is known to disrupt sleep regulation by interfering with the brain’s ability to smoothly transition between sleep stages, as inflammatory chemicals affect the same brain regions that control wakefulness and rest.
People with inflammatory bowel diseases often experience this connection in very practical ways.
Cortisol Levels and Distress Signals
Inflammation also raises levels of cortisol, the stress hormone, making the body feel alert and ready for action instead of rest.
Stress, sleep, and gut health continuously interact. Stress alters the gut microbiome by reducing beneficial bacteria and increasing inflammatory compounds. The disturbed gut then sends distress signals to the brain, heightening anxiety and worsening sleep.
Lack of sleep, in turn, increases cortisol levels, further aggravating gut imbalance. This creates a vicious cycle that is difficult to break unless gut health is properly supported.
Al Arabiya
