Scientists have pinpointed a surprising culprit behind millions of people’s sleepless nights – and it’s not stress, caffeine or uncomfortable pillows. The problem lies deep within your gut, where trillions of bacteria may be directly controlling whether you get a good night’s rest or toss and turn until dawn.
In groundbreaking research published in the medical journal General Psychiatry, Chinese researchers have discovered that certain types of gut bacteria can either promote healthy sleep or trigger chronic insomnia. The massive study analysed data from nearly 400,000 people, making it the first to establish a direct causal link between specific gut microbes and sleep disorders.
Study lead Shangyun Shi from Nanjing Medical University concluded there appears to be a “complex two-way relationship” between gut bacteria and insomnia risk, with the sleep disorder itself also altering which bacteria thrive in the digestive system.
Bacteria That Help You Sleep vs Those That Don’t
The research team compared data from 386,533 people with insomnia against microbiome studies totalling 26,548 individuals who had 71 groups of bacteria in common. Using sophisticated genetic analysis techniques, they identified specific bacterial culprits and heroes in the battle for better sleep.
The analysis revealed 14 groups of bacteria were positively associated with insomnia, increasing the odds by 1-4 per cent. Meanwhile, 8 groups of bacteria appeared protective, lowering insomnia risk by 1-3 per cent.
Most intriguingly, insomnia itself changed the gut microbiome composition. The sleep disorder was linked to a dramatic reduction of 43 to 79 per cent in seven groups of beneficial bacteria, while causing a more than four-fold increase in 12 other bacterial groups.
Dr Shi told BBC Science Focus that this research had the potential to “reshape understanding of insomnia and inspire interest in microbiome-based research and interventions.
The Odoribacter Connection
One bacterial group stood out in particular – the odoribacter class, which showed a significant association with insomnia risk. This finding is particularly important because odoribacter bacteria are known for producing short-chain fatty acids, especially butyrate, which have wide-ranging health benefits.
“Odoribacter plays a role in producing short-chain fatty acids like butyrate, which influence inflammation, neurotransmitter balance and circadian regulation,” gastroenterologist Lindsey Ann Edwards of King’s College London told Newsweek.
High levels of odoribacter are typically linked with good gut health and lower inflammation throughout the body. Conversely, lower levels have been observed in people living with inflammatory bowel disease (IBD), obesity and type 2 diabetes – all conditions that frequently involve sleep problems.
The bacteria produce butyrate and other beneficial compounds that serve as energy sources for intestinal cells, maintain gut barrier function, and have anti-inflammatory effects that extend throughout the body, including the brain.
How Your Gut Talks to Your Brain
The research builds on growing evidence of the “gut-brain axis” – a complex communication network linking your digestive system with your central nervous system. This biological highway allows gut bacteria to influence everything from mood to metabolism, and now, scientists know it includes sleep regulation.
Previous studies have shown that gut bacteria can produce or influence neurotransmitters like serotonin and GABA, which play crucial roles in sleep regulation. The microbes also affect inflammation levels throughout the body, which can disrupt normal sleep patterns when elevated.
In fact, recent research from Molecular Psychiatry found that transplanting gut bacteria from insomnia patients into germ-free mice caused the animals to develop insomnia-like behaviours. The mice showed decreased levels of butyrate in their blood, and their sleep problems were reversed when they were given butyrate supplements.
Future Treatments Could Target Your Gut
Ms Shi said the findings open exciting possibilities for treating insomnia through the gut microbiome rather than traditional sleeping pills. Future treatments could include probiotics, prebiotics, dietary changes or even faecal microbiota transplantation.
“Additionally, the gut microbiome may serve as a biomarker to track how well these treatments work, enabling more personalised care,” Shangyun explained.
The research suggests that instead of reaching for sleeping tablets, insomniacs might benefit from treatments that restore healthy gut bacteria. This could involve specific probiotic strains known to produce butyrate and other sleep-promoting compounds.
Some studies have already shown promising results. Japanese research found that the probiotic Blautia wexlerae improved metabolic health in patients with obesity and diabetes – conditions closely linked to both gut dysbiosis and sleep problems.
What You Eat Affects Your Sleep
The connection between gut bacteria and sleep also highlights the importance of diet in managing insomnia. Dr Emily Prpa, a registered nutritionist at Yakult, explained that diet is one of the strongest influences on gut bacteria composition.
The types of fibre and plant diversity in the diet can shift bacterial populations sometimes even within days,” Dr Prpa told Newsweek. “Lifestyle factors such as exercise and alcohol intake also play a role.
Foods that promote beneficial bacteria include:
- High-fibre vegetables and fruits
- Fermented foods like yoghurt and sauerkraut
- Whole grains and resistant starch
- Prebiotic-rich foods like garlic, onions and leeks
Meanwhile, processed foods, excess sugar and alcohol can promote the growth of bacteria associated with inflammation and poor sleep.
Study Limitations Point to More Research Needed
While the findings are groundbreaking, Ms Shi acknowledged several limitations that require further exploration. All study participants were of European descent, which is significant because microbiome composition varies among different ethnicities and geographical regions.
Furthermore, the research didn’t account for lifestyle factors such as diet and exercise, which are known to affect both the microbiome and sleep quality. The interplay between genes and environment also wasn’t fully explored.
Despite these limitations, the research represents a major advance in understanding the biological mechanisms underlying insomnia. It suggests that the estimated one-third of Britons and Americans who experience insomnia might benefit from treatments targeting their gut bacteria rather than just their brains.
The Bigger Picture
The discovery adds to mounting evidence that many chronic health conditions involve disruptions to the gut microbiome. Previous research has linked gut bacteria to depression, anxiety, obesity, diabetes and inflammatory conditions – many of which also involve sleep disturbances.
Scientists at The Affiliated Brain Hospital of Nanjing Medical University used sophisticated Mendelian randomisation techniques to prove causation rather than just correlation. This means they could show that certain bacteria actually cause sleep problems, not just that they happen to be present in people with insomnia.
The research also revealed that the relationship works both ways – while certain bacteria can cause insomnia, having insomnia changes your gut bacteria composition, potentially creating a vicious cycle that’s hard to break without intervention.
As researchers continue to unravel the complex relationships between our microbiomes and health, it’s becoming clear that the trillions of microbes living within us are far more than passive passengers – they’re active participants in virtually every aspect of our wellbeing, including whether we get a good night’s sleep.
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Image Credit (Shortened):
Depiction of a person suffering from insomnia (sleeplessness, Dec 2019) — by MyUpchar.com, licensed under CC BY‑SA 4.0, via Wikimedia Commons.
