A potential cure for the debilitating condition irritable bowel syndrome (IBS) is now a step closer, following a landmark scientific discovery that explains why women are disproportionately affected.
The Hormonal Link to Gut Pain
Researchers from the University of California, San Francisco (UCSF) have made a significant breakthrough, identifying a precise biological mechanism that makes women up to twice as likely to suffer from the lifelong digestive disorder. The study, published in the prestigious journal Science, centres on the female sex hormone oestrogen.
While previous studies had hinted that oestrogen might slow gut movement, this new research goes further. The team discovered that oestrogen receptors—proteins that boost the hormone's effects—are densely clustered in the lower colon. Here, they stimulate specific cells known as L-cells to release a hormone called PYY.
Crucially, the scientists found that PYY directly activates painful nerve fibres in the gut, a role never before described. In experiments on mice, blocking both oestrogen and PYY resulted in a 'dramatic reduction' of gut pain in females.
From Diet Management to Future Drug Therapies
This discovery also sheds light on why the current NHS-recommended low-FODMAP diet helps some IBS patients. Foods high in FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) can trigger symptoms. Common examples include:
- Broccoli, beans, and lentils
- Wheat and garlic
- Onions, apples, and some fruit juices
The researchers suggest that eating fewer of these foods may prevent L-cells from producing excessive pain-signalling PYY. However, as study co-author Dr Holly Ingraham, a professor of molecular and cellular pharmacology at UCSF, notes, "Even for patients who see success with a low-FODMAP diet, it's nearly impossible to stick to long term."
Dr Eric Figueroa, an expert in pharmacology and physiology at UCSF, emphasised the importance of the finding: "Establishing this new role for PYY in gut pain reframes our thinking about this hormone and its local effects in the colon."
A New Path for Treatment and Understanding
The research provides the first rigorous scientific explanation for the gender disparity in IBS. To confirm the link, the scientists gave male mice oestrogen to match female levels—their gut pain sensitivity promptly increased to match that of females.
Dr Ingraham stated the team's goal was clear: "Instead of just saying young women suffer from IBS, we wanted rigorous science explaining why. We've answered that question, and in the process identified new potential drug targets."
This opens the door to developing medications that target these newly identified pathways, offering hope for the estimated one in five UK adults with IBS. The condition most commonly affects people aged 20-39 and symptoms, which vary in severity, include:
- Stomach pain, bloating, diarrhoea, and constipation
- Fatigue, nausea, and back pain
- Passing mucus in stool and urinary problems
With many sufferers not seeking medical advice, experts believe this prevalence could be a significant underestimation. This groundbreaking work moves the focus from symptom management to targeting the root cause of pain, promising a future where effective, targeted drugs could replace lifelong dietary restrictions.
