A study from the University of Tsukuba in Japan revealed that people who have healthy gut microbes get better sleep. With so many people suffering from insomnia worldwide, this research could provide some relief. Many factors influence sleep, including stress levels, eating habits, and physical health, to name a few. However, the common link between all of these is the microbiome, which governs all functions in the body.

All illnesses can be traced back to the gut because 70% of our immune system is manufactured here. This may explain our chronic disease epidemic since many people today have poor gut bacteria due to various lifestyle factors. The study by Japanese scientists shows the importance of a healthy gut because it influences everything from our moods to sleep patterns.

About the gut microbes study

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In the study, researchers used various antibiotics in order to deplete the gut microbes in mice. They discovered that metabolites in the gut differed in these mice compared with controls. Specifically, metabolic pathways involved in creating neurotransmitters such as serotonin became disrupted. Furthermore, the mice showed abnormal sleeping patterns and disruptions in their circadian rhythm. In particular, their REM sleep became disrupted; the mice seemed to slip in and out of REM sleep quite frequently.

The study, led by Professor Masashi Yanagisawa in Japan, aims to show the extent that gut health impacts our lives. The thorough study in mice revealed how significantly gut microbes can alter the intestines and affect behaviors such as sleep.

For the experiment, the researchers gave a group of mice various powerful antibiotics for a period of four weeks. This depleted their gut microbes. Then, the researchers compared the intestinal contents of these mice and the control group who ate the same diet. In the digestion process, food gets broken down into small pieces called metabolites.

What the study revealed about how gut microbes influence sleep

The team found striking differences between the metabolites in the mice with no gut microbes and the control group.

Professor Yanagisawa said, “We found more than 200 metabolite differences between mouse groups. 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.”

Next, the team wanted to determine how the metabolites act under normal conditions. Using metabolome set enrichment analysis, they discovered that the antibiotics mostly affected biological pathways involved in making neurotransmitters. Cells in the brain use these molecules to communicate with each other.

In the mice, researchers found that their tryptophan-serotonin pathway had basically stopped functioning. While the mice with depleted gut microbes had more tryptophan than controls, they had almost no serotonin. This observation proves that when the gut lacks important bacteria, tryptophan can’t get converted to serotonin. Furthermore, the team found that the mice had low levels of vitamin B6 metabolites, which aid the production of serotonin and dopamine.

Other observations

Next, the team observed the sleep quality of the mice by using EEGs to study brain activity. They found that the microbiota-depleted mice had more REM and non-REM sleep at night than the control mice. The mice also had less non-REM sleep during the day. While this would look normal for humans, it shows a flipped circadian rhythm in the mice, who are nocturnal animals.

The occurrence of REM sleep episodes increased both during the day and night. However, the number of non-REM episodes increased only during the day. Researchers say this shows that the microbiota-depleted mice alternated between sleep/wake stages more often than the controls.

Professor Yanagisawa suggested that depleted serotonin levels caused the sleep disturbances. However, they still need to do more research to determine the exact mechanism behind this phenomenon.

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

Other studies that show how healthy gut microbes can prevent insomnia

Similar studies yielded related findings.

1. Having a healthy gut helps your neurotransmitters and hormones stay balanced, which ensures a good night’s sleep.

In fact, one study found that beneficial gut microbes can lower cortisol levels, which play a huge role in hormone production. Too much cortisol results in imbalanced hormones, which can affect sleep quality and duration.

Also, a healthy gut ensures that your body will produce adequate GABA, an amino acid that helps with sleep. Finally, since 90% of serotonin comes from our gut, having good bacteria will help you relax at bedtime.

2. Melatonin levels also play an important role in the quality of our sleep.

When our bodies have healthy levels of this hormone, our sleep-wake cycles are consistent. However, in our modern world, many people’s circadian rhythms have been thrown off due to lack of sunlight. Also, the bright blue lights emitted from smartphones and computers deplete melatonin levels at night. This could explain the increase in insomnia since the advent of mobile technology in the past 20 years.

To increase the body’s melatonin levels, it’s important to eat foods high in tryptophan, since this converts to serotonin. You can also take probiotics, since these increase melatonin levels by increasing tryptophan in the body. People with low levels of serotonin often have disrupted circadian rhythms due to imbalanced melatonin.

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Final thoughts: Gut microbes play an important role in the quality of our sleep

Scientists have just begun to discover the link between our gut microbiome and sleep disorders. Not surprisingly, the study of mice proved that having an unhealthy gut caused sleep disruptions. The mice who had depleted gut bacteria had a flipped circadian rhythm, and we see that in humans today as well. Many people feel wired at night when they should start feeling sleepy from a long day at work.

However, by taking care of our gut bacteria and eating healthy foods, we can start getting better sleep. In general, you’ll want to avoid processed foods and eat whole foods to feed the good bacteria.