Fact v fiction: Stress and your gut

Stress - especially long-term stress - is known to for its harmful effects on health, but how much does it affect the gut? We asked Gastroenterology Dietitian Dr Sammie Gill to separate the facts from the fiction. 

Fact: Stress often manifests in the gut, with both short- and long-term stress associated with disruptions to normal gut function. 

Stress stimulates the release of hormones such as adrenaline and noradrenaline, which can have a dual effect on gut motility - either speeding it up or slowing it down. This can lead to changes in poo habits, resulting in either diarrhoea or constipation. 

What’s more, lab studies in mice suggest that stress can influence different regions of the gut in distinct ways. For instance, short-term stress may reduce motility in the lower part of the large intestine while the upper part continues to contract. 

Fiction: Higher amounts of stress is associated with an increased risk of irritable bowel syndrome (IBS).  

Stress is also linked with worsening symptoms in IBS, partly because it can increase visceral hypersensitivity, or sensitivity to pain in the gut.  

Stress has been associated with the development of other gut conditions too, including inflammatory bowel disease (IBD), partly driven by increased gut permeability and localised inflammation. Stress also seems to trigger flare ups.  

Fiction: The gut microbiome is highly sensitive to changes in stress levels. For instance, increased stress is linked with decreases in key bacterial groups, such as Proteobacteria and Verrucomicrobia, as well as beneficial microbes, such as Lactobacillus and Bifidobacterium. 

When the types of microbes shift, so do the metabolites they produce. In fact, studies have shown that stress reduces levels of short-chain fatty acids (SCFAs) – key metabolites that provide a source of energy for cells that line the gut and help suppress the growth of potentially harmful gut microbes. 

What’s more, SCFAs have been shown to affect gut motility, and lab studies in mice indicate that SCFA supplementation can reduce the stress response, lower stress-like behaviours, and decrease gut permeability.  

Although still in its early stages, this is where gut microbiome–targeted interventions may offer promise. 

Fact: Short-term stress can disrupt normal gut barrier function and increase gut permeability (or ‘leakiness’). That said, this effect is short-lived and resolves once the stressor is removed.  

In contrast, longer-term stress can lead to sustained gut ‘leakiness’ which can disrupt immune function and trigger inflammation locally and throughout the body.  

This is tied to a higher risk of developing gut-related conditions and worsening symptoms, such as abdominal pain, bloating, and changes in poo habits. 

Fiction: Not all stress is harmful. Short-term stress is usually transient and arises from immediate challenges or demanding situations. It leads to short-lived physiological changes such as increases in adrenaline and changes in poo habits (e.g. a bout of diarrhoea).   

Long-term stress differs because it persists over time. It can have cumulative effects on the body and increase the risk of several chronic health conditions, inside the gut (e.g. IBS) and outside the gut (e.g. cardiovascular disease).  

More studies are needed on head-to-head comparisons between different stressor types (e.g. traumatic, environmental, psychological, physiological) and their effects on the gut.  

Fiction: For many years, the gut and brain were viewed as separate systems. Today, we know this isn’t the case at all. 

In fact, the gut and the brain have a very close relationship and are in constant communication with one another – called the ‘gut-brain connection’. 

Stress in one can quickly affect the other.  

The gut and the brain ‘talk’ using four key channels – the nervous system, the hormonal system, the gut microbiome, and the immune system. 

Learn more about the gut-brain connection here. 

Summary 

Stress affects the gut in different ways – from changes in motility to changes in microbes.  

Managing stress over the long-term is important for protecting the health of your gut and beyond.  

Prioritising stress management by addressing triggers, developing effective coping skills, and setting aside regular ‘me time’ - can be helpful.  

Sources 

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective. The Journal of Physiology. (2023). Link. 

Sympathetic input to multiple cell types in mouse and human colon produces region-specific responses. Gastroenterology. (2022). Link. 

Negative events during adulthood are associated with symptom severity and altered stress response in patients with irritable bowel syndrome. Clinical Gastroenterology and Hepatology. (2019). Link. 

Systematic review with meta-analysis: The association between post-traumatic stress disorder and irritable bowel syndrome. Journal of Gastroenterology and Hepatology. (2018). Link. 

Stress-induced chronic visceral pain of gastrointestinal origin. Frontiers in Systems Neuroscience. (2017). Link. 

Systematic review: the role of psychological stress in inflammatory bowel disease. Alimentary Pharmacology and Therapeutics. (2022). Link.