Struggling to get enough sleep? Chronic sleep deprivation is relatively common. The Centers for Disease Control & Prevention notes that around 35 percent of U.S. adults get less than seven hours of slumber a night, and a lack of sleep can affect a number of bodily functions, from your attention and memory to your coordination. However, there's another area you may not have considered: how a lack of sleep can mess with your gut health. The gut microbiome, or the colony of bacteria that help digest our food, control our metabolism, influence immune function and inflammation, and hundreds of other jobs in the body, can get imbalanced without enough sleep.
Sleep specialist Dr. Michael Breus told The Guardian in 2018 that "the microbial ecosystem may affect sleep and sleep-related physiological functions in a number of different ways: shifting circadian rhythms, altering the body’s sleep-wake cycle, affecting hormones that regulate sleep and wakefulness." However, the connection also goes the other way. How you sleep, and particularly how much sleep you get, affects the variety and diversity of microbes flourishing in your gut — and that has knock-on effects for your health more widely.
So how does lack of sleep affect your gut? A review of the science in Frontiers in 2018 lays it out: a variety of sleep disturbance issues, like "circadian clock misalignment, sleep deprivation, and shift experience" (that's when you have shift work that messes up your internal 24-hour clock), cause changes in the gut, including its "microbial community structure."
The bacteria in your colon are in a delicate balance, and it seems that sleep deprivation interferes with it through making certain bacteria die off and others proliferate. A study in Nature in 2016 used mice to see what sleep fragmentation, or waking up a lot in the night and ending up sleep-deprived, did to their gut bacteria. The results, they found, were "preferential growth of highly fermentative members of Lachnospiraceae and Ruminococcaceae and a decrease of Lactobacillaceae families." Doesn't sound like a lot, but the researchers noted that those changes led to tissue inflammation and changes in insulin sensitivity in the mice.
They also did two more experiments: they found that the intestinal barrier tissue of sleep-deprived mice was 'leaky', letting more bacteria out of the gut, and they also passed microbiota from the sleep-deprived mice into other, healthy mice, and saw that it affected their inflammation and insulin resistance as well. It was clearly the microbiota at fault, not something else, and it was capable of causing issues in mice who hadn't even lost sleep.
Various other animal studies have backed up these findings. One study in 2018 looked at rats, and found that sleep-deprivation drugs reduced "the richness and diversity of the microbiota in the colon," and slowed down the amount of mucus the colon secretes (sounds disgusting, but we need it for the colon to function). Another study in 2013 found that disrupting the circadian clock in mice — the 24-hour internal clock that regulates when we sleep and wake up — led to more intestinal permeability, or leakiness. And evidence is gathering that suggests sleep deprivation can indeed alter insulin sensitivity in humans, though it's not clear whether the gut is the primary reason this happens.
Even short-term sleep deprivation can change how your gut works. A study in 2016, the European Society for Neurogastroenterology and Motility reported, found that in healthy young men, sleep deprivation over just two nights rearranged their gut microbes. The guts of the sleep-deprived men showed higher levels of Firmicutes, Coriobacteriaceae and Erysipelotrichaceae bacteria and a dip in Tenericutes bacteria. The scientists wrote that there need to be "further investigations in larger and more prolonged sleep studies" to see what these alterations might do to the metabolism and other issues, but their work shows that, small though the changes might be, sleep deprivation over just one weekend can change your gut.
More research needs to be done to see what exactly the shifts in the microbiome from sleep deprivation do to our long-term health, and how long it takes the gut to recover from poor sleep. However, if you happen to have insomnia, work night shifts, or sleep badly, it's worth looking after your gut with lots of fermented foods, prebiotics, and a balanced diet.