Insomnia and your gut: what recent research shows

If you've tried every sleep hygiene trick and still lie awake most nights, your gut might be part of the story. For the fundamentals, see our overview of sleep and your gut. Sleep research spent decades focused almost entirely on habits and brain chemistry, leaving out the trillions of microbes in your digestive tract that make up your microbiome. In the last few years, several new studies have linked chronic insomnia directly to shifts in that microbial community. None of this replaces treatments that already work for insomnia; it adds one more real, testable factor you and your doctor can look at.

Your gut looks different when you cannot sleep

A 2025 review pulled together 15 case-control studies covering more than 1,300 people with insomnia and matched good sleepers.^[1] About half of those studies found lower microbial diversity in people with insomnia, meaning fewer distinct types of bacteria doing fewer distinct jobs. Two groups tied to gut health, Faecalibacterium and Lachnospira, ran lower in people with insomnia, while Blautia ran higher. Researchers also found that the more severe someone's insomnia, the wider that gap tended to be.

Which comes first, restless gut or restless nights?

A 2025 genetic study looked at insomnia data from 386,533 people alongside gut bacteria data from more than 26,000 additional participants, using a method called Mendelian randomization.^[2] That method leans on the random way genes shuffle between parents and children, closer to a natural experiment than a survey ever gets. Fourteen bacterial groups appeared to raise insomnia risk and eight appeared to lower it, though every effect was small, changing the odds by only one to four percent. Insomnia itself also seemed to reshape the gut, cutting some bacterial groups by up to 80 percent and roughly quadrupling others. After correcting for testing so many bacteria at once, only one species, Clostridium innocuum, held up as a clear, statistically robust link to insomnia risk.

Small effect. Real effect. A method built specifically to rule out reverse causation makes this more convincing than a plain correlation study, even with modest numbers. All the participants were of European descent, so it's not yet clear how well this holds up across other populations. Taken together, the current research points to a modest, two-way relationship between your gut bacteria and your sleep, not one single explanation for either. We look at a related angle in when your schedule shifts, your gut feels it too.

How your gut reaches your brain at night

Gut bacteria break down tryptophan, an amino acid found in food like turkey, eggs, and nuts, into building blocks your body uses to make serotonin and melatonin, the two chemicals most responsible for making you feel calm and sleepy. Your gut microbes don't produce melatonin or serotonin themselves. They prepare the raw materials your body needs to build both, giving this gut-brain link an actual physical route rather than a pattern that just happens to line up. A 2024 study in mice found that bacterial metabolites made from tryptophan and a related amino acid, phenylalanine, boosted melatonin production and extended how long the mice slept.^[3] Human research on this exact pathway is still catching up, but the mouse data gives scientists something concrete to test next.

Probiotics for sleep: promising, not proven yet

Early clinical trials are starting to test specific probiotic strains for sleep, and the results so far are encouraging without being conclusive. In a 2023 randomized, placebo-controlled trial, 40 adults with stress-related insomnia took either a strain called Bifidobacterium breve CCFM1025 or a placebo for four weeks.^[4] Researchers traced part of the improvement to lower cortisol, the stress hormone that ramps up when you're wired and keeps you from settling into sleep.

One small trial isn't proof the strain works for everyone, but it's a concrete, science-backed signal. No probiotic is currently approved as a treatment for insomnia, and none of this should replace cognitive behavioral therapy for insomnia, known as CBT-I. CBT-I retrains the thoughts and habits that keep insomnia going, and the American College of Physicians recommends it as the first treatment to try for chronic insomnia, ahead of medication.^[5]

What you can do tonight

None of this means you should self-treat insomnia with supplements or skip a sleep evaluation if you need one. It does mean you should mention your gut next time you talk to a doctor about ongoing insomnia. Naps factor into this rhythm too; see napping, your body clock, and your gut. If chronic insomnia has dragged on for months, ask about CBT-I first, and treat your gut as a genuine, science-backed extra, not a replacement.

• Stop eating at least 3 hours before bed, so digestion isn't competing with your body's sleep signals
• Cut caffeine by early afternoon; it lingers 5 to 8 hours and can blunt the same tryptophan pathway your gut uses to build melatonin
• Work a fermented food, kefir, yogurt, or sauerkraut, into a meal earlier in the day rather than right before bed
• Build toward more fiber-rich foods this week, since fiber feeds the bacteria that help make your serotonin and melatonin building blocks
• Keep a consistent wake time, even on weekends, to steady your gut's internal clock along with your brain's
• Go easy on alcohol close to bedtime; it disrupts sleep architecture and gut bacteria in the same overnight window