Does your gut microbiome affect how well you sleep?
Your gut microbiome and your sleep mutually influence each other, but how to practically steer that through probiotics or supplements is still too inconsistent to recommend concretely. Less ultra-processed food and more fibre and plant-based products are the best-supported starting points.
Gut bacteria produce substances that directly contribute to sleep regulation. Some bacteria produce calming compounds such as GABA and melatonin, while others produce activating compounds such as serotonin or cortisol. That balance partly determines how easily you fall asleep and how deeply you sleep.
The relationship also runs in the other direction: if you sleep poorly or not enough, your gut microbiome itself becomes unbalanced. Sleep fragmentation and sleep deprivation activate the stress hormone system, which negatively affects the composition of your gut bacteria. Certain bacteria that subsequently increase in number in turn produce substances that amplify fatigue. This is a cycle that can sustain itself, although the evidence for this is still limited.
Chronic disruption of your circadian rhythm -- caused by, for example, night shifts, jet lag, or a high-fat, high-sugar diet -- also impairs the daily rhythm of your gut bacteria. Time-restricted eating, in which you consume your meals within a fixed window of the day, appears to be able to partially restore that rhythm.
Can you improve your sleep by targeting your microbiome? Probiotics containing lactobacilli and bifidobacteria showed a positive effect on how quickly you fall asleep and how long you sleep in some studies, but other studies found no difference. The evidence is too inconsistent at this point to base a concrete recommendation on. A fibre-rich, plant-based diet with polyphenols and unsaturated fats appears to stimulate more sleep-promoting substances, but that too has not been studied well enough in humans to make firm statements. Omega-3 supplementation is linked to better sleep in small studies, although the connection with the microbiome has barely been examined in those studies.
What is clear: eating a lot of ultra-processed food is associated with a 41% higher risk of sleep problems. This is an association, not a proven causal relationship, but it fits the broader pattern: what you eat affects your gut, and your gut affects your sleep.
Based on multiple review studies and one meta-analysis (PMID 38418082 on ultra-processed food). Causality in humans has not yet been conclusively demonstrated for most of the relationships described. Probiotic studies are inconsistent. Dietary studies are largely observational.