Diet and stool tests may help predict IBD flares, study finds

Regular stool tests already used in NHS care, combined with dietary information, could help identify people with inflammatory bowel disease (IBD) at higher risk of relapse, a major study suggests.  

Researchers found that elevated gut inflammation detected by stool tests – even when people felt well – strongly predicted future disease flares. 

The study also found that higher meat consumption was linked to an increased risk of relapse in people with ulcerative colitis, though not in Crohn’s disease.  

Experts say embedding this approach to treatment of IBD could potentially allow earlier intervention and help personalise care to those most at risk. 

Inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, affects nearly one per cent of the UK population. People often experience long periods of remission, followed by sudden and debilitating flares of symptoms such as pain, diarrhoea and fatigue. 

Many patients ask whether everyday diet plays a role in triggering flares, but robust evidence has been limited, experts say. 

To address this, University of Edinburgh researchers led the PREdiCCt study, which followed 2,629 people with IBD who reported being in remission at the start of the study. Participants were recruited from 47 NHS centres between 2016 and 2020. 

At enrolment, participants completed a food-frequency questionnaire and provided clinical information, including blood tests and a stool test measuring faecal calprotectin – a marker of gut inflammation. They then completed monthly symptom questionnaires and were followed for a median of four years. 

Researchers recorded both symptom-based flares and ‘objective’ flares, where inflammation was confirmed by tests and treatment needed to be escalated. 

They found that faecal calprotectin was a strong early warning signal, even when people felt well. Higher levels at baseline were linked to a much greater risk of future flares. 

In ulcerative colitis, the chance of an objective flare within two years increased from around 11 per cent in people with low calprotectin levels to 34 per cent in those with high levels. 

They also found that diet was linked to flare risk in ulcerative colitis. People who consumed the most meat had around double the risk of an objective flare compared with those who ate the least. This pattern was not seen in Crohn’s disease, and there were no consistent links between flares and fibre intake, ultra-processed foods, polyunsaturated fats or alcohol. 

Experts say that because PREdiCCt is an observational study, it cannot prove that eating meat causes flares. However, they believe the findings support future clinical trials to test whether reducing meat intake, alongside routine inflammation monitoring, could help prevent relapses in ulcerative colitis.  

Charlie Lees, Professor of Gastroenterology at the University of Edinburgh: “This major study is the first of its kind to properly track the relationship between habitual diet and disease flares in such a large, prospective way. It has been a massive team effort over the past decade to recruit and follow more than 2,600 people living with IBD across the UK. Our results provide a new framework for management: using objective biomarkers to catch subclinical inflammation early and identifying specific dietary factors that may help prevent debilitating relapses. This is exactly the kind of personalised evidence-base we need to improve the lives of people living with Crohn’s and colitis.” 

The study, which is published in the journal Gut: https://doi.org/10.1136/gutjnl-2025-337846 [URL will become active after embargo lifts], also involved nutrition researchers from the University of Aberdeen. It was funded by UK Research and Innovation (UKRI), the Scottish Government’s Chief Scientist Office and Cure Crohn’s Colitis.