Gut Health and Sleep: Exploring the Gut–Brain–Sleep Connection

Sleep and gut health may seem like two separate topics, but they are closely connected. They have a bidirectional relationship, meaning each can influence the other. This connection can affect sleep quality, mood, stress levels, digestion and overall wellbeing. Read on to learn more about the relationship between sleep and the gut, and which probiotics and nutritional approaches may be best for stress, sleep and digestion.

The relationship between sleep and the gut

Sleep and the gut have a bidirectional relationship. Poor sleep can impair gut microbiota composition and function, while gut dysbiosis can disrupt sleep quality and duration¹. The gut microbiome is regulated by circadian rhythms through intrinsic bacterial clocks and host signals. Microbiome rhythmicity appears to function as a secondary internal clock that works alongside the brain’s clock to help regulate the sleep-wake cycle².

The gut-brain axis is a bidirectional network that connects gut microbes to the central nervous system (CNS), helping regulate sleep architecture and homeostasis. The axis operates through multiple routes, which can all influence neurotransmitter production, including serotonin and gamma-aminobutyric acid (GABA)²:

• Metabolic pathways, including short-chain fatty acids such as butyrate and bile acids such as lithocholic acid.
• Neural pathways, including the vagus nerve.
• Immune-endocrine signalling.

How poor sleep affects the gut

Poor sleep, whether due to sleep deprivation, insomnia, poor sleep quality, or very short or very long duration, can negatively affect gut health. Poor sleep may alter gut motility and contribute to digestive symptoms such as bloating, abdominal pain, diarrhoea or constipation³.

Poor sleep may reduce microbial diversity, including the loss of beneficial taxa such as Lactobacillus and Bifidobacterium. It may also exacerbate dysbiosis and increase inflammation due to over-representation of potentially pro-inflammatory species⁴.

Sleep deprivation can also elevate cortisol levels and activate the hypothalamic-pituitary-adrenal (HPA) axis. This may contribute to increased intestinal permeability, inflammation and disruption of the gut microbiome⁵. Longer sleep durations have also been linked to increased cortisol levels alongside insulin resistance⁶.

Sleep quality and the gut microbiome

The gut microbiome plays an important role in sleep quality and overall health through the gut-brain axis⁷. Gut microbes produce metabolites such as short-chain fatty acids, serotonin, GABA, melatonin and tryptophan, while also modulating host pathways that generate these molecules⁷.

These metabolites help influence circadian rhythms, nervous system signalling and sleep architecture, and their production is strongly shaped by diet quality and meal timing⁷. If the balance of gut bacteria is disrupted, this may negatively affect microbial diversity and has been linked with sleep disturbances, sleep conditions and chronic inflammation⁷.

Lifestyle factors affecting sleep and gut health

When considering the relationship between sleep and gut health, it is important to think about lifestyle factors that could influence both:

• Diet quality and meal timing: High-quality diets, including more fibre and less sugar, and eating earlier are associated with better metabolic health and less circadian disruption. Late-night eating is linked to poorer sleep quality^8,9.
• Stress and nervous system activation: Chronic stress activates the HPA axis and sympathetic nervous system, increasing cortisol, which can impair gut barrier integrity and alter microbiota composition¹⁰.
• Physical activity: Regular movement supports better sleep and is associated with a more favourable gut microbial profile. Sedentary behaviour has been linked to poorer sleep and less diverse microbiota¹¹.
• Alcohol and nicotine: Both substances have been shown to increase sleep fragmentation if consumed within four hours of bedtime¹².
• Antibiotic exposure and microbiome disruption: Antibiotics can disrupt gut microbial diversity and composition, affecting brain-gut signalling. A case report highlighted antibiotic-induced dysbiosis as a hidden cause of chronic insomnia¹³.

Probiotics for sleep: what does the evidence show?

Probiotics have been widely investigated for their potential effects on sleep, mood and stress. Here is a breakdown of key literature for some of the potentially best probiotics for sleep:

• Lactiplantibacillus plantarum LP815: A clinical trial involving adults with self-reported sleep disturbance found that supplementation significantly improved subjective insomnia scores, anxiety and objective wearable sleep measures. Urinary GABA rose significantly within the first week of use and was inversely correlated with insomnia and anxiety scores¹⁴.
• Multi-strain probiotic containing Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01 and Bifidobacterium longum 04: A clinical trial in healthy adults found that multi-strain probiotic supplementation improved subjective ability to fall asleep faster and reduced disturbances during sleep, resulting in improved overall sleep quality as assessed by the Pittsburgh Sleep Quality Index (PSQI)¹⁵.
• Bifidobacterium longum 1714: A clinical study involving adults with impaired sleep quality found that this strain significantly improved the PSQI sleep quality component and daytime dysfunction due to sleepiness, while also improving social functioning and energy/vitality¹⁶.
• Limosilactobacillus reuteri PBS072 and Bifidobacterium breve BB077: In a clinical trial involving healthy adults working at a university after the COVID-19 pandemic, this multi-strain probiotic significantly reduced Profile of Mood States (POMS) and PSQI scores, indicating improvements in sleep quality and mood¹⁷.
• Lacticaseibacillus paracasei Lpc-37: In a clinical trial involving adults with high or low chronic stress, this probiotic reduced perceived stress and, in high chronic stress participants, improved perceived health and sleep-related recovery¹⁸.
• Lactobacillus gasseri CP2305: In young adults under chronic academic stress, supplementation in tablet form reduced anxiety and sleep disturbance scores, shortened sleep latency and wake after sleep onset, and attenuated stress-related shifts in gut microbiota by lowering Streptococcus and preserving Bifidobacterium¹⁹. In another clinical trial using a drink formulation, this strain shortened sleep latency and increased sleep duration in men²⁰.
• Lactobacillus casei Shirota: In healthy students exposed to academic stress, daily fermented milk containing this strain helped maintain sleep quality by improving subjective sleepiness on rising and sleep length, preserving deep sleep and preventing stress-related increases in sleep latency²¹.

While research in this area is promising, most studies have been carried out in healthy individuals or people experiencing stress, rather than those with diagnosed sleep disorders. Benefits also appear to be strain-specific, so findings from one product cannot be applied to all probiotics. For now, probiotics for sleep, stress and mood should be viewed as a supportive option.

Nutritional strategies to support sleep and gut health

• Fibre-rich food: Fibre from vegetables, fruits, whole grains, legumes, nuts and seeds can support regular bowel movements and fuel beneficial bacteria that produce short-chain fatty acids. In a clinical study, higher dietary fibre intake reduced the risk of sleep disorders⁸.
• Fermented foods: Foods such as yoghurt, kefir, kimchi and sauerkraut provide live microbes and bioactive compounds that can enhance microbial diversity and influence neurotransmitter production. In a clinical study, pasteurised fermented milks improved sleep quality in adults²².
• Stable blood glucose patterns: Balanced evening meals that combine complex carbohydrates with protein, healthy fats and fibre are thought to stabilise nocturnal blood glucose and may reduce sleep fragmentation²³.
• Daytime hydration: Adequate daytime hydration can support digestion and bowel regularity. However, excessive fluid intake late in the evening may increase night-time bathroom trips, also known as nocturia²⁴.
• Limited caffeine intake: Caffeine is best limited in dose and cut off sufficiently early, often at least six hours before bed, to minimise its impact on sleep onset, total sleep time and sleep depth^25,26.
• Holistic lifestyle support: Nutritional strategies work best alongside regular exercise, daylight exposure, stress management and consistent sleep-wake times. These behaviours can help synchronise circadian rhythms and stabilise the gut microbiome³.

Clinical takeaways

So, can gut health affect sleep? Yes, the gut microbiome and sleep are closely interconnected. Sleep disruption may negatively affect the gut microbiome, while gut imbalances may influence sleep, stress and mood.

Certain probiotics may help support sleep in some people, but evidence for probiotics for sleep is still emerging. Probiotics are best viewed as an adjunct alongside fibre-rich foods, fermented foods, stable blood glucose, daytime hydration, circadian rhythm support and established sleep advice and treatments.

References

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