Gut Microbiota Aids Sleep and Enhances Health (Part One)

The cold of winter poses only a temporary threat to those with cardiovascular and cerebrovascular conditions, and can be mitigated with simple precautions. However, there is one daily activity that is often overlooked yet profoundly impacts the health of such patients—sleep! Multiple studies indicate that good sleep quality can reduce the risk of cardiovascular disease, while insufficient or poor-quality sleep may lead to cardiovascular issues such as elevated blood pressure and arrhythmia. To lower the risk of cardiovascular disease or improve its current state, maintaining good sleep quality is crucial!

Normal physiological sleep

Normal physiological sleep comprises the following five stages: Stage One sleep (transition between wakefulness and sleep); Stage Two sleep (decrease in body temperature, slowing of heart rate); Stage Three sleep (transition from light to deep sleep); Stage Four sleep (slow brain waves); Stage Five sleep (rapid eye movement sleep, REM).

Sleep commences in this standard sequence but subsequently cycles through these stages in an irregular pattern. Whilst contemporary medical advice recommends securing at least eight hours of sleep, the actual duration is less critical than ensuring completion of four to five full sleep cycles.

Criteria for Insomnia and Factors Affecting Sleep

Insomnia is the most prevalent sleep disorder. The criteria for diagnosing insomnia are:

1. Time taken to fall asleep [exceeding 30 minutes]
2. Difficulty maintaining sleep [ Taking over 30 minutes to return to sleep after waking ]
3. Early awakening [ Waking over 30 minutes earlier than usual ]
4. Occurring more than three times per week for conditions 1–3
5. Impaired social functioning and physical discomfort the following day

Factors affecting sleep quality and duration are as follows, with numerous internal and external elements capable of disruption. While many causes contribute to sleep disorders, one often overlooked factor is the gut microbiota.

Gut Microbiota and Sleep Are Closely Linked

The gut-brain axis facilitates bidirectional communication through immune regulatory pathways, neuroendocrine pathways, and the vagus nerve pathway. When gut microbiota becomes disrupted and harmful bacteria proliferate, various neurotoxic metabolites enter the brain via the vagus nerve. This consequently impacts brain function, stress responses, and sleep. A study published in Frontiers in Psychiatry reveals that gut microbiota not only influence the host's digestion, metabolism, and immune function but also regulate sleep and mental states through the microbiota-gut-brain axis.

Gut microbiota produce GABA metabolites, a natural amino acid and the body's safest sedative. These possess inherent sleep-inducing, anti-anxiety, and anti-depressant properties. Gut microbiota can stimulate intestinal production of sleep-regulating neurotransmitters such as serotonin (5-hydroxytryptamine) and dopamine, thereby improving sleep disorders.

Furthermore, most gut microbial populations produce short-chain fatty acids—particularly butyrate—which ultimately form butyrate salts in the body to promote sleep progression.

The gut microbiome's circadian rhythm influences the body's biological clock

Every organ and cell within the body possesses its own biological clock, and the microbiota within the gut is similarly governed by circadian rhythms.

Staying up late and disrupted sleep patterns affect the composition and health of the gut microbiota. Each instance of late nights forces the body's trillions of gut bacteria like Bifidobacterium animalis subsp. lactis F1-7

to operate outside their natural rhythm, potentially leading to the proliferation of harmful bacteria and damaging the intestinal mucosa.

Diet, Microbiota, Circadian Rhythms and Sleep Disorders

We often hear that healthy eating, lifestyle choices and sensible dietary habits benefit both mental and physical wellbeing.It is understandable that spicy foods, stimulants, and adverse food reactions (intolerances and allergies) affect sleep. But why are skipping meals, eating too quickly or excessively, irregular meal times, and poor food quality also dietary causes of sleep disorders? Fundamentally, dietary intake relates to gut microbiota composition, as the food we consume serves as the primary substrate for microbial growth. Alterations in our diet may reshape our gut microbiota within days.

Disruptions to feeding rhythms and circadian timing induce time-specific changes in gut bacteria, ultimately leading to dysbiosis. This disrupted microbiota then influences sleep quality via the gut-brain axis.