5 Ways Your Gut Health Can Mess With Your Sleep, According To Science

A small amount of sleep loss can pretty immediately change the composition of your gut microbiome. Sleep doctor Dr. Michael Breus wrote that a small study of nine healthy young men in 2016 found "a significant decrease in types of beneficial bacteria" and changes in the microbiome after just two nights of sleep deprivation. It was only a small study, but it indicates that when we sleep poorly, our gut suffers and can't do its job as efficiently.

Every human has a 'body clock': an internal 24-hour set of rhythms that determine when we wake up and when we sleep, among other processes in our body. That clock is maintained by every cell in the body, and the gut is no different. Recent studies have discovered that gut bacteria has a big role to play in regulating this body clock, and therefore in how much we sleep. A fascinating 2016 study found that gut microbes move around according to a rhythm during the day and night, and therefore influence the circadian rhythms of other organs; in a press release, the scientists called it a "dance."

We also know how powerful gut microbes can be when it comes to sleep rhythms. A 2014 study of jet-lagged humans and mice found that sleep disruption affected how well the microbes worked — and when the gut microbes from jetlagged humans were implanted into mice, the mice began to show signs of malfunctioning guts, like high blood sugar levels. More recently, a 2018 study from Washington State University looked at how shift work, which often disrupts our circadian rhythms by making us adapt to odd sleeping patterns, affects the gut. Three days of shift work, the study found, was enough to 'shift' the body clocks in the gut and pancreas, causing metabolic issues and a disconnection from the 'master' body clock we all have in our brains.

Scientists have established in recent years that the gut microbiome may be linked to mental health; a recent study found that people with depression have very distinct gut bacteria levels. However, it seems that sleep has a role in this relationship, too. Professor Tim Spector, geneticist and gut specialist, told The Guardian in 2018, “We know that people who live with depression and people who sleep poorly both have abnormal microbes in the gut, which would suggest there is a very real connection here between all three. I’ve always found that if you help someone sleep, it improves their depression, and vice versa. If we can also look after the gut, this may have an impact on both sleep disturbances and mood disorders.”

The connection between the gut, the brain and sleep is likely to be the gut-brain axis. The gut has its own nervous system, and it 'talks' to our brains — and gets a response. Through this "bidirectional communication system between the central nervous system and the gastrointestinal tract", explained a study in 2016, "the gut microbiome can also influence neural development, cognition and behaviour, with recent evidence that changes in behaviour alter gut microbiota composition, while modifications of the microbiome can induce depressive-like behaviours" [sic].

A study in 2018 suggested that people who have insomnia linked to their depression could blame their gut for it. The research theorizes that people who experience depressive insomnia might have gut bacteria that are over-stimulating nerves and tissues, causing the central nervous system to go haywire and producing depressive symptoms and sleep issues. It's an interesting theory, but a lot more work needs to be done to prove it.

If you have irritable bowel syndrome, a disorder of the gut and bowels, you'll likely also experience sleep issues. That's the conclusion of the International Foundation of Gastrointestinal Disorders. "People with chronic pain report sleep as their number one problem," they wrote. "Certainly, abdominal pain, and pain from any source, can cause difficulty sleeping as well as arousals from sleep and consequent sleep fragmentation." However, the link between IBS and poor sleep isn't just about pain.

VeryWell Health notes that different sleep hormone levels have been observed in people with different kinds of IBS; constipation-predominant IBS and diarrhea-predominant IBS affect sleep in specific neurological ways, though it's not clear why. Gastrointestinal disorders can also affect the body's inflammatory response, which seems to cause sleep issues. Scientists wrote in a study in 2015: "Proinflammatory cytokines [immune system cells], such as tumor necrosis factor, interleukin-1, and interleukin-6, have been associated with sleep dysfunction. Alterations in these cytokines have been seen in certain gastrointestinal diseases, such as gastroesophageal reflux disease, inflammatory bowel disease, liver disorders, and colorectal cancer." Not only does IBS lead to poor sleep, poor sleep may also raise the risk of experiencing gastrointestinal issues like IBS.

If an unhealthy gut can influence sleep, it stands to reason that a healthy gut can make us all sleep like babies — and science says that's true. A study of rats in 2017 found that prebiotics — not probiotics, which are live bacteria, but fiber and fiber-containing foods that feed the bacteria in your gut — can help sleep. The study gave rats prebiotics after exposing them to stress, and found that it helped them restore a normal sleep pattern and get restful ZZZs with more REM sleep. The lesson here is that if you've experienced sleep disruption due to stress, it's a good idea to eat prebiotic substances — garlic, onions, leeks, asparagus and bananas are on the list, according to Healthline.

The link between the gut and sleep is a pretty strong one. We're still discovering the ins and outs of its complexities, but it's a safe bet to assume that if you're having sleep issues your gut is involved — and that if your gut is suffering, your sleep likely will, too.