Gut Microbes: A Key To Normal Sleep

Gut microbes are a community of bacteria, viruses, and fungi living in your gut. A recent study shows gut bacteria could play a role in sleep patterns. (1,2)

The Relationship Between Gut Health And Sleep 

The study’s lead author, Professor Masashi Yanagisawa of the University of Tsukuba in Japan suggests gut bacteria help create important chemical messengers in the brain. The findings of the study could provide insights to assist those suffering from poor sleep or sleep-related issues from insomnia to mental fog. (1,2)

“We found that microbe depletion eliminated serotonin in the gut, and we know that serotonin levels in the brain can affect sleep-wake cycles,” says Prof. Yanagisawa. “Thus, changing which microbes are in the gut by altering diet has the potential to help those who have trouble sleeping.” (1,2)

Gut Health And Sleep-Wake Cycles

The team built off of existing studies appearing in Scientific Reports establishing that elements of cognition and brain development are strongly linked with intestinal microbial health and metabolism. Natural functions such as circadian rhythms and eating are vital biological processes or functions. Circadian rhythms are based on a 24-hour cycle using the body’s internal clock triggering our sleep-wake cycles. When these are off, it causes sleep disturbances. (3,1)

The Gut-Brain Axis

The “brain-gut axis” or “microbiota-gut-brain axis” is the connection between intestinal metabolism and brain function through the circulatory system and vagus nerve. The gut microbiome affects elements of the brain function, including the circadian rhythm. Because diet affects gut microbiota, these changes can change intestinal metabolism. The microbes in microbiota create gut metabolites which are molecules resulting from the chemical reactions occurring during the digestive process. (1,2)

As a result, if diet changes, it could improve or reduce sleep problems. If this is true, diet could become a simple alternative treatment to sleep medications. However, the study is yet to be applied to human subjects. The study at the university in Japan looked at mice. (1,2)

Gut Health And Sleep In Mice

Some mice were given water with broad-spectrum antibiotics to deplete the mice’s gut microbiota. Research showed these mice had fewer intestinal metabolites. “We found more than 200 metabolite differences between mouse groups,” says Prof. Yanagisawa. “About 60 normal metabolites were missing in the microbiota-depleted mice, and the others differed in the amount — some more and some less than in the control mice.” (1,2)

Antibiotics And Gut Health

As well, the antibiotic treatment most affected were those that help produce the molecules used by neurons to communicate called neurotransmitters. The study showed that the antibiotics: (1,2)

  • Totally shut down the tryptophan-serotonin pathway.
  • Caused higher tryptophan levels, but almost no serotonin.
  • Showed deficiency in vitamin B6 metabolites required to speed up serotonin and dopamine production.

As a result, researchers concluded gut microbes are critical to change the tryptophan in foods to serotonin. (1,2)

Gut Health And Sleep Results

The brains of the mice showed: (1,2)

  • More rapid eye movement (REM) and non-REM sleep at night, when mice are typically active. 
  • Less non-REM sleep during the daytime when mice tend to sleep. 
  • A higher number of REM sleep episodes during the night and day.
  • A higher number of non-REM episodes in the daytime. 

The study suggests the noted sleep disturbances could relate to low serotonin levels. However, more research is required to help determine the mechanism. Future research will also see if the findings are true for humans. (1,2)

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