Good sleep starts in the gut. An increasing number of studies confirm the key role of the microbiota in regulating sleep, mood, and stress resilience. Experts note that disruptions in the composition of gut microbes can cause insomnia, pre-sleep anxiety, and disturbances in circadian rhythms, The Conversation reports.

The gut and the brain are connected by a complex network of signals — the so-called “gut–brain axis.” Its most well-known component is the vagus nerve, which provides two-way communication. According to research, increased vagus nerve activity promotes a calmer nervous system tone and smoother transitions into sleep.

But neural pathways aren’t the only factor. Gut microbes produce a variety of biologically active substances — from metabolites to neurotransmitters that influence sleep-related hormones. Most of the body’s serotonin, which regulates daily cycles, is synthesized in the gut. Melatonin, responsible for nighttime sleepiness, is produced there as well. Some beneficial bacteria generate GABA, the main inhibitory neurotransmitter that reduces anxiety. Together, these substances form the basis of the body’s internal clock.

When microbial balance is disrupted — a condition known as dysbiosis — signaling becomes chaotic. This affects sleep, leading to difficulty falling asleep and nighttime awakenings. Another crucial mechanism is inflammation. A healthy microbiota maintains the integrity of the gut lining and regulates immune responses. When the epithelium is damaged (due to stress or poor diet, for example), inflammatory molecules enter the bloodstream, affecting brain centers responsible for wakefulness and disrupting sleep architecture.

The so-called “leakage” of gut toxins triggers elevated cortisol — the stress hormone that prepares the body for action rather than rest. This creates a vicious cycle: stress alters the microbiota, a disrupted gut increases anxiety, and poor sleep raises cortisol even further, destabilizing the microbial balance.

Improving gut health, according to recent data, directly enhances sleep quality. Prebiotic- and probiotic-rich foods, especially fermented ones, help restore beneficial bacteria. Reducing sugar and ultra-processed foods lowers inflammation. Regular eating patterns support the gut’s internal biorhythms, and adequate hydration strengthens the protective mucosal layer of the gut lining.

Researchers emphasize that good sleep begins long before a person goes to bed. It is the result of the gut’s complex physiological work throughout the day. When the microbiota is in balance, the brain can more easily switch into rest mode, and nighttime cycles become deeper and more restorative.