Study: Cryan JF, O’Riordan KJ, Sandhu KV and colleagues. “The Microbiota–Gut–Brain Axis.” Published in Nature Reviews Gastroenterology & Hepatology, 2023.

Scientists have increasingly discovered that the gut and brain are closely connected through what researchers call the microbiota–gut–brain axis. This refers to the communication network linking the digestive system, the nervous system, and the brain.

A major review published in Nature Reviews Gastroenterology & Hepatology in 2023 explored how microbes living in the digestive tract influence this communication system.

Gut microbes produce a wide range of substances that can interact with the body. Some of these compounds affect immune activity, while others influence nerve signalling. Signals from the gut can also travel directly to the brain through the vagus nerve, which acts as a communication pathway between the digestive system and the nervous system.

Through these pathways, the gut microbiome can influence how the body responds to stress and how the brain regulates mood and emotional resilience.

What this means

This research highlights that the microbes living in the gut are not only involved in digestion but are also part of a broader communication system connecting the gut, immune system, and brain.

Why this matters for people with digestive symptoms

Many people with digestive issues also experience stress, anxiety, or mood changes. Research increasingly suggests that the gut and brain are closely linked systems, and changes in the gut environment may influence both digestive health and emotional wellbeing.

Study: Valles-Colomer M, Falony G, Darzi Y and colleagues. “The neuroactive potential of the human gut microbiota in quality of life and depression.” Published in Nature Microbiology, 2019.

Researchers have increasingly explored how the gut microbiome may influence mental health. A study published in Nature Microbiology in 2019 examined links between specific gut bacteria and measures of mood and quality of life in large human populations.

The researchers found that certain types of gut bacteria were consistently associated with higher quality of life, while others were linked to symptoms of depression. These associations remained even when accounting for factors such as medication use.

The study also identified that some gut bacteria are involved in producing compounds that can influence the nervous system, including substances linked to neurotransmitter activity.

This helped strengthen the evidence that the gut microbiome may play a role in how the brain regulates mood and emotional wellbeing.

What this means

The gut microbiome is linked to brain function and may influence mood through biological signalling pathways.

Why this matters for people with digestive symptoms

Many people with digestive issues also experience changes in mood or stress levels. This research helps explain why these experiences often occur together and highlights the close connection between gut health and emotional wellbeing.

Study: Moloney RD, Stilling RM, Dinan TG, Cryan JF. “The microbiome and stress-related disorders: an emerging link.” Published in Biological Psychiatry, 2016.

Researchers have increasingly explored how chronic stress affects the digestive system. A study published in Biological Psychiatry examined how stress can influence gut function through interactions between the nervous system, immune system and microbiome.

The researchers found that prolonged stress can alter the gut environment in several ways. It can increase intestinal permeability, meaning the gut barrier becomes more sensitive, and can also activate immune pathways that increase inflammation.

Stress was also shown to influence the composition of the gut microbiome, which may further affect how the gut and brain communicate.

These changes help explain why stress can have a direct impact on digestive function, even in the absence of clear structural disease.

What this means

Chronic stress can influence gut function by affecting the gut barrier, immune activity and microbiome.

Why this matters for people with digestive symptoms

Many people notice that their symptoms worsen during periods of ongoing stress. This research helps explain why stress can trigger or maintain digestive symptoms, reinforcing the importance of supporting both the gut and the nervous system.

Study: Suez J, Korem T, Zeevi D and colleagues. “Artificial sweeteners induce glucose intolerance by altering the gut microbiota.” Published in Cell, 2015.

For many years, nutrition advice has been based on the idea that the same foods affect everyone in similar ways. A landmark study published in Cell in 2015 challenged this assumption and helped introduce the concept of personalised nutrition.

The researchers found that individuals can have very different blood sugar responses to the same foods. These differences were partly influenced by the composition of the gut microbiome.

In the study, some participants experienced negative metabolic responses to artificial sweeteners, while others did not. These responses were linked to changes in gut bacteria, suggesting that the microbiome plays a role in how the body processes food.

This research showed that dietary responses are not universal and can vary significantly between individuals.

What this means

The way your body responds to food is influenced by your unique biology, including your gut microbiome.

Why this matters for people with digestive symptoms

Many people find that certain foods trigger symptoms while others tolerate them well. This research helps explain why there is no single “perfect diet” for everyone, reinforcing the importance of a personalised approach to nutrition rather than following generic guidelines.

Study: Zeevi D, Korem T, Zmora N and colleagues. “Personalized nutrition by prediction of glycemic responses.” Published in Cell, 2015.

For many years, nutrition advice has assumed that people respond to food in broadly similar ways. A landmark study published in Cell in 2015 challenged this idea by showing that individual responses to food can vary significantly.

The researchers tracked blood sugar responses in a large group of people after eating the same meals. They found that some individuals had stable responses, while others experienced sharp spikes, even when eating identical foods.

These differences were partly explained by variations in the gut microbiome, along with other individual factors such as lifestyle and physiology. The researchers were able to predict how people would respond to certain foods using personalised data.

This study helped demonstrate that metabolic responses to food are highly individual rather than universal.

What this means

Your response to food is influenced by your unique biology, including your gut microbiome and lifestyle factors.

Why this matters for people with digestive symptoms

Many people find that certain foods affect them differently over time. This research supports the idea that there is no single diet that works for everyone, highlighting the importance of a personalised approach to nutrition rather than following generic rules.

Study: Marco ML, Cunningham M, Bischoff SC and colleagues. “The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of gut health.” Published in Nature Reviews Gastroenterology & Hepatology, 2026.

The term “gut health” is widely used, but until recently it has not had a clear scientific definition. A 2026 consensus statement brought together an international panel of experts to define what gut health actually means in research and clinical practice.

The group defined gut health as a state of normal digestive function without ongoing symptoms or active disease that affects quality of life. Importantly, this definition recognises that gut health is not just about test results, but also about how a person feels day to day.

The researchers also highlighted that gut health is complex. Someone can have a diagnosed condition but still experience good gut health during periods of remission. Equally, someone may have no clear diagnosis but still experience symptoms that impact their wellbeing.

They also emphasised that many current tests, including microbiome testing, do not yet reliably reflect overall gut health or predict how someone feels.

What this means

Gut health cannot be defined by a single test, diagnosis, or symptom. It is a combination of function, lived experience, and overall wellbeing.

Why this matters for people with digestive symptoms

This helps explain why digestive issues can feel inconsistent or difficult to measure. It also reinforces the importance of a personalised approach that considers both clinical findings and your experience, rather than relying on one test or label alone.

Study: Cox TO, Devason AS, de Araujo A and colleagues. “Intestinal interoceptive dysfunction drives age-associated cognitive decline.” Published in Nature, 2026.

Scientists are increasingly discovering that the gut and brain communicate constantly. A study published in Nature in 2026 explored how changes in the gut may influence memory and brain health as we age.

The research focused on communication between the digestive system and the brain through the vagus nerve, a major nerve that carries signals from organs throughout the body to the brain. These signals help the brain monitor what is happening inside the body, including digestion, inflammation, and the state of the gut microbiome.

Researchers found that certain gut bacteria that increase with age produce substances that trigger inflammation in immune cells. This inflammation can interfere with signals travelling from the gut to the brain through the vagus nerve.

When this communication weakens, activity declines in the hippocampus, the region of the brain responsible for forming and storing memories. In their experiments, restoring healthy gut signalling improved memory performance in older animals.

What this means

This study suggests that the gut microbiome plays an important role in maintaining communication between the body and the brain.

Why this matters for people with digestive symptoms

Although this research focused on ageing, it reinforces an important principle: the gut and brain are closely connected systems, and changes in the gut environment can influence health far beyond digestion.

Study: Zhang Z, Ren S, Fan X and colleagues. “Chronic psychological stress-orchestrated glial-ILC3 circuit exacerbates intestinal inflammation and depression.” Published in Brain, Behavior, and Immunity, 2025.

Researchers are increasingly investigating how long-term psychological stress affects both the gut and the brain. A study published in Brain, Behavior, and Immunity in 2025 explored how chronic stress can influence immune activity in the digestive system.

The researchers examined how stress affects communication between the nervous system and immune cells in the gut. They found that prolonged stress can alter the activity of certain support cells within the nervous system that interact with immune cells in the intestine.

These changes can activate immune pathways that increase inflammatory signalling in the gut. Over time, this may contribute to ongoing intestinal inflammation and changes in how the gut and brain communicate with one another.

The study also observed that these biological changes may influence both digestive symptoms and emotional wellbeing, reinforcing the idea that the gut and brain function as interconnected systems.

What this means

This research suggests that long-term stress may influence gut inflammation through interactions between the nervous system and immune cells in the digestive tract.

Why this matters for people with digestive symptoms

For many people with ongoing digestive issues, symptoms can worsen during periods of prolonged stress. This study helps explain how chronic stress may contribute to inflammation in the gut and why managing stress can be an important part of supporting digestive health.

Study: Zhou X, Wang S, Wang X and colleagues. “Mechanisms of the effect of gut microbes on depression through the microbiota–gut–brain axis.” Published in Frontiers in Nutrition, 2025.

Scientists have increasingly been exploring how microbes living in the digestive tract influence the brain. A study published in Frontiers in Nutrition in 2025 examined how the gut microbiome may affect mood and emotional wellbeing through the microbiota–gut–brain axis.

The microbiome refers to the trillions of microbes that live in the digestive system. These microbes produce a wide range of substances that can interact with the body, including compounds that influence immune activity, inflammation, and nerve signalling.

Researchers found that signals produced by gut microbes can reach the brain through several pathways. These include communication through the nervous system, signalling through the immune system, and substances produced by microbes that circulate through the bloodstream.

Through these mechanisms, the gut microbiome may influence how the brain regulates mood and responds to stress.

What this means

This research highlights how microbes in the gut are involved in communication between the digestive system and the brain.

Why this matters for people with digestive symptoms

Many people with digestive issues also experience changes in mood, stress levels, or emotional wellbeing. Research increasingly suggests that the gut microbiome may play a role in this connection, reinforcing how closely gut health and overall wellbeing are linked.

Study: Schneider KM, Blank N, Alvarez Y and colleagues. “The enteric nervous system relays psychological stress to intestinal inflammation.” Published in Cell, 2023.

Researchers have long observed that many people with digestive conditions experience flare-ups during periods of stress. A major study published in Cell in 2023 helped explain the biological reason why this happens.

The researchers focused on the enteric nervous system, the complex network of nerves embedded throughout the digestive tract. Sometimes referred to as the “second brain,” this system constantly communicates with the brain and helps regulate digestion, immune activity, and gut movement.

The scientists discovered that chronic psychological stress increases levels of stress hormones such as cortisol. These hormones can change how the nerves in the gut behave. Instead of simply coordinating digestion, the stressed nervous system begins sending signals that activate immune cells in the intestine.

These immune cells release inflammatory molecules, including tumour necrosis factor, which increase inflammation in the digestive tract. The researchers also found that stress can disrupt nerve signalling that controls gut movement, which may contribute to symptoms such as bloating, abdominal pain, diarrhoea, or constipation.

What this means

This research shows that stress can influence gut inflammation through communication between the brain, the nervous system in the gut, and the immune system.

Why this matters for people with digestive symptoms

Many people notice their gut symptoms worsen during periods of stress. This study helps explain why supporting both gut health and the nervous system may be important when addressing ongoing digestive issues.

Study: La Torre D, Van Oudenhove L, Vanuytsel T, Verbeke K. “Psychosocial stress-induced intestinal permeability in healthy humans: What is the evidence?” Published in Neurobiology of Stress, 2023.

The lining of the digestive tract plays an important protective role in the body. It acts as a barrier that allows nutrients from food to enter the bloodstream while preventing bacteria, toxins, and other unwanted substances from passing through the gut wall.

A study published in Neurobiology of Stress in 2023 explored how psychological stress can affect this barrier. Researchers reviewed evidence showing that stress can temporarily increase intestinal permeability, meaning the gut lining becomes more permeable than normal.

When the gut barrier becomes more permeable, substances that usually stay within the digestive tract may pass more easily into the bloodstream. This can trigger immune responses and increase inflammation in the body.

The researchers also found that stress can influence biological pathways that regulate the structure and integrity of the intestinal lining, affecting how well the gut barrier functions.

What this means

This research provides evidence that psychological stress can affect the physical structure and function of the gut barrier.

Why this matters for people with digestive symptoms

Many people with digestive issues notice that their symptoms worsen during stressful periods. This study helps explain why stress may contribute to digestive flare-ups or increased sensitivity in the gut.

Study: Chan KL, Poller WC, Swirski FK, Russo SJ. “Central regulation of stress-evoked peripheral immune responses.” Published in Nature Reviews Neuroscience, 2023.

Scientists are increasingly exploring how the brain influences immune activity throughout the body. A review published in Nature Reviews Neuroscience in 2023 examined how stress signals from the brain can regulate immune responses in organs such as the gut.

When the brain perceives stress, it activates signalling pathways through the nervous system. These signals travel throughout the body and influence how immune cells behave. In response to stress, the body may increase inflammatory activity as part of its protective response.

While this process can be useful in short-term situations, repeated or chronic stress may lead to sustained immune activation. Over time, this increased inflammatory activity may affect tissues and organs throughout the body, including the digestive system.

The researchers highlight that the brain, nervous system, and immune system are closely interconnected and constantly communicating with each other.

What this means

This research shows that stress does not only affect how we feel emotionally. It can also influence immune activity and inflammation throughout the body.

Why this matters for people with digestive symptoms

Many digestive conditions involve inflammation in the gut. Understanding how stress signals influence immune responses helps explain why managing stress can be an important part of supporting digestive health and overall wellbeing.

Study: Solano JL, Menard C. “A gut feeling: The stressed brain drives intestinal inflammation.” Published in Immunity, 2023.

Scientists have increasingly discovered that the brain and digestive system are closely connected. A paper published in Immunity in 2023 explored how stress signals originating in the brain can influence inflammation in the gut.

When the brain perceives psychological stress, it activates signalling pathways through the nervous system. These signals travel through networks that connect the brain to organs throughout the body, including the digestive tract. One of the key systems involved is the communication between the brain and the gut’s nervous system.

The researchers describe how stress signals can influence immune cells in the intestine. When these signals are activated repeatedly or over long periods of time, immune activity in the gut may increase, leading to higher levels of inflammation.

This growing body of research highlights how closely the nervous system and immune system are linked, and how stress signals from the brain can affect physical processes throughout the body.

What this means

The brain and digestive system communicate constantly, and stress can influence immune activity in the gut through this connection.

Why this matters for people with digestive symptoms

Many digestive conditions involve inflammation in the gut. Understanding how stress signals can influence immune responses helps explain why stressful periods often coincide with worsening digestive symptoms.

Study: Cryan JF, Dinan TG. “Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour.” Published in Nature Reviews Neuroscience, 2012.

Over the past decade, scientists have increasingly explored how the gut and brain communicate. Foundational research by John Cryan and Ted Dinan helped establish the concept that microbes living in the digestive tract can influence brain function, stress responses and behaviour.

This work describes how the gut microbiome interacts with the nervous system through multiple pathways. These include communication via the vagus nerve, signalling through the immune system, and the production of microbial compounds that can affect brain activity.

The researchers showed that changes in the microbiome can influence how the body responds to stress, as well as emotional and behavioural patterns. This helped establish the idea that the gut and brain are part of an integrated system rather than separate processes.

This research has since become a foundation for understanding the gut–brain connection.

What this means

The gut microbiome plays a role in how the brain responds to stress and regulates emotional and physiological processes.

Why this matters for people with digestive symptoms

Many digestive conditions are influenced by stress and the nervous system. This research helps explain why symptoms can be closely linked to emotional and physiological states, reinforcing the importance of addressing both gut health and nervous system regulation.