Barley bran is sometimes used as a dietary intervention for Irritable Bowel Syndrome (IBS), primarily due to its high fiber content. Scientific evidence supports that increased dietary fiber can help with some IBS symptoms, particularly constipation-predominant IBS (IBS-C). Barley bran is a source of insoluble fiber, which can increase stool bulk and speed up intestinal transit time. Several studies have investigated the effects of bran (from various grains, including barley and wheat) on IBS, with mixed results.

A 2014 review in the World Journal of Gastroenterology noted that insoluble fiber such as bran can improve constipation but may worsen symptoms like bloating and abdominal discomfort in some IBS patients. In contrast, soluble fibers (e.g., psyllium) are generally better tolerated and more effective for overall IBS symptom relief. Some randomized controlled trials have found that while bran can relieve constipation, it may exacerbate other IBS symptoms in a significant proportion of patients.

In summary, there is moderate scientific evidence (rating: 3/5) supporting the use of barley bran for constipation-dominant IBS, but it is not universally recommended for all IBS patients due to the potential for increased bloating and discomfort. Clinical guidelines now often favor soluble fiber over insoluble fiber like bran for most IBS cases.