Recent studies indicate that we’re experiencing a “sleep crisis” in the UK. A significant portion of us are sleeping less than the recommended 7–9 hours, often averaging between 6 and 7 hours per night. Around 36% of people consider their sleep to be “good” quality; only 3% wake feeling completely refreshed, and 57% feel tired or lack energy during the day.
As many as one in seven adults do not get enough sleep to function properly on any day in a typical week.
Feedback on modern sleep patterns tells a familiar story: high stress levels, reliance on caffeine, and widespread use of technology before bed. We live in what many describe as a “tired but wired” culture.
We also know now that poor sleep has a significant impact on both mental and physical health. What is becoming increasingly clear is that gut health is part of this story.
There is a strong, bidirectional relationship between the gut microbiome and sleep which is often referred to as the microbiota–gut–brain axis. This means that the state of our gut health can affect our sleep, and poor sleep can, in turn, negatively impact our gut bacteria.
It is not a one-way street. It is a feedback loop.
How does poor sleep affect health?
The effects of poor sleep vary between individuals. It may show up as irritability, sugar cravings or falling asleep on the train. But these everyday frustrations are often the surface of something deeper.
Long-term sleep deprivation has been associated with serious impacts across multiple systems in the body.
1. Brain and mental health
Chronic sleep loss affects cognitive performance. Research shows that insufficient sleep impairs attention, memory, learning and decision-making. Over time, persistent sleep restriction has been linked to structural changes in the brain.
Sleep is also tightly connected to mood regulation. Poor sleep is associated with an increased risk of anxiety and depression. In fact, insomnia is now considered both a symptom and a risk factor for mood disorders.
Even one poor night’s sleep can affect emotional control, making us more reactive, impulsive and less resilient to stress.
2. Cardiovascular and metabolic health
Ongoing sleep deficiency raises the risk of heart disease, high blood pressure and stroke. Large cohort studies published in journals such as The Lancet and European Heart Journal have shown consistent links between short sleep duration and cardiovascular risk.
Sleep also plays a role in metabolic health. Insufficient sleep alters glucose metabolism, increasing the risk of type 2 diabetes. It disrupts appetite hormones, raising levels of ghrelin (which stimulates hunger) and lowering leptin (which signals fullness). The result is often increased cravings for calorie-dense foods.
Long-term lack of sleep is now recognised as a risk factor for obesity.
3. Immune function
Sleep is when much of our immune regulation takes place.
A lack of quality sleep can weaken immune defences, lowering the production of protective cytokines. Studies show that individuals who sleep less than six hours per night are more likely to develop a cold when exposed to a virus compared with those sleeping seven hours or more.
Poor sleep does not just make you feel run down; it changes how your immune system behaves.
What is the link between gut health and sleep?
The gut microbiome, the trillions of microbes living in our digestive tract, is deeply involved in regulating many of the systems mentioned above.
A randomisation study published in 2023 suggests reciprocal links between certain gut bacteria and insomnia risk. Some microbial patterns appear to increase susceptibility to sleep disturbances, while insomnia itself alters the abundance of specific bacterial species.
Again, it is circular.
Microbial diversity and sleep quality
Studies have shown that greater gut microbial diversity is associated with longer total sleep time and improved sleep efficiency which is the proportion of time in bed actually spent asleep.
Chronic insomnia has been linked to reduced microbial diversity and shifts in specific bacterial families. A less diverse microbiome may be less resilient, potentially contributing to inflammation and stress signalling that disrupt sleep.
Diversity builds stability.
Neurotransmitters and hormones
The gut is not just involved in digestion. It is a biochemical factory.
· Around 90% of the body’s serotonin is produced in the gut. Serotonin is a precursor to melatonin, which is the hormone that regulates the sleep–wake cycle.
· Tryptophan metabolism, which influences both serotonin and melatonin production, is shaped by gut bacteria.
· Certain strains of Lactobacillus and Bifidobacterium produce gamma-aminobutyric acid (GABA), a neurotransmitter that promotes relaxation and sleep.
If gut microbial balance shifts, these signalling pathways may also shift.
Mechanisms of influence
The gut and brain communicate through multiple channels:
· The vagus nerve
· Immune signalling
· Hormonal pathways
· Short-chain fatty acids (SCFAs) produced when microbes ferment dietary fibre
SCFAs, such as butyrate, help regulate inflammation and influence brain function. Chronic low-grade inflammation has been associated with sleep disturbance.
Cortisol, which is our primary stress hormone, also interacts with the microbiome. Disrupted circadian rhythms and high stress can alter microbial composition, and microbial imbalance can in turn influence cortisol regulation.
Research suggests that as little as two nights of poor sleep may shift microbial balance, creating the beginnings of a vicious cycle.
Sleep affects the gut. The gut affects sleep.
How can I get better sleep?
The research increasingly suggests that microbiome-inspired approaches may form part of future treatment plans for insomnia. Emerging clinical studies are exploring whether specific probiotics or prebiotics can improve sleep quality by supporting microbial balance and reducing inflammation.
While this field is still developing, the broader principles are well established.
Sleep thrives on rhythm, balance and restoration.
Practical steps include:
· Going to bed and waking up at the same time each day to regulate circadian rhythms.
· Creating a dark, cool and quiet bedroom environment.
· Limiting caffeine, nicotine and alcohol in the evening.
· Avoiding heavy meals before bed.
· Reducing blue light exposure by stepping away from screens at least an hour before sleep.
· Building wind-down rituals like reading, stretching, journaling or simply slowing down.
· Exercising regularly, but not intensely just before bed.
· Getting natural daylight exposure during the day.
And importantly:
Supporting your gut.
A diet rich in fibre, diverse vegetables, fruit and whole foods feeds beneficial microbes. Fermented foods and live probiotics may help maintain microbial balance, particularly during periods of stress.
The aim is not to chase sleep. It is to create the conditions for sleep to emerge naturally.
The bigger picture
Sleep is not an isolated function. It is woven into our immune health, metabolism, mental resilience and microbiome balance.
When we neglect sleep, the effects ripple outward.
When we restore it, healing begins in multiple systems at once.
Perhaps the real insight here is this: sleep is not just about the brain. It is about the whole ecosystem of the body.
And that ecosystem begins in the gut.
Here’s to enjoying the deep, restorative sleep you deserve.
References
World Health Organization (2023) Sleep and Health Overview.
