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SAN ANTONIO -- Symptoms associated with moderate or severe irritable bowel syndrome (IBS) improved significantly at 12 weeks in adult patients who consumed a supplement containing human milk oligosaccharides (HMOs), a prospective open-label study showed.

The overall IBS severity score decreased by 55%, ranging from 49-62% across the three principal IBS subtypes. Abdominal pain severity and frequency, bloating, and gastrointestinal symptom severity all improved significantly, as did health-related quality of life (QoL).

Most of the improvement occurred during the first 4 weeks and was maintained to the end of the study, Magnus Simren, MD, of the University of Gothenburg in Sweden, reported here at the American College of Gastroenterology meeting.

"Oral supplementation with a blend of [two HMOs] can provide nutritional support for individuals with IBS of all subtypes," said Simren, currently a visiting faculty member at the University of North Carolina in Chapel Hill. "The supplementation was associated with reduced abnormal stool consistency, improved overall bowel symptom severity, reduced abdominal pain and bloating, and improved health-related quality of life."

The vast majority of patients rated the supplement product as "well tolerable" or "tolerable" throughout the 12-week study period, he added.

Altered gut microbiota appear to be a contributing factor to IBS pathophysiology. Several studies have shown altered intestinal microbiota composition and function, altered gut barrier function, and altered intestinal symptoms in patients with IBS. Interventions that restore intestinal microbiota composition and function might reduce IBS symptoms and improve disease status, said Simren.

HMOs are the of gut microbiota status in infants. HMOs are involved in the maturation of the gut barrier and development of gut immune function. They also bind pathogens to prevent attachment to infant mucosal surfaces and lower the risk of viral, bacterial, and protozoan parasite infections.

"In patients with IBS and healthy volunteers, we have demonstrated that HMOs specifically increase bifidobacteria abundance," said Simren. "This is of great importance because these bacteria are considered to be important for a healthy gut and have been found to be reduced in patients with IBS. HMOs also increase the concentration of metabolites essential for gut barrier functioning and immune modulation. From a safety perspective, it is important that they do not induce gastrointestinal symptoms."

Simren reported findings from the multicenter, single-arm trial to assess the potential of a blend of two HMOs to support bowel habits and improve bowel symptoms and quality of life in patients with IBS. The oral supplement contained 5 grams of 2'-Fucosyllactose (2'FL) and lacto-N-neotetraose (LNnT) and was consumed daily. The product is commercially available (Holigos IBS) without a prescription but is designed for physician-supervised use.

Investigators at 17 sites in the U.S. enrolled patients with a physician diagnosis of IBS who met Rome IV criteria. Data analysis included 317 patients with a mean age of 44; 70% were women.

Simren said 136 patients had constipation-predominant IBS, 85 had diarrhea-predominant IBS, 95 had mixed symptoms, and IBS subtype was not specified in one case. Two thirds of the patients had an IBS diagnosis for 1-3 years, and a fourth had an IBS duration ≥5 years. Almost two-thirds of the patients had severe illness by the IBS Symptom Scoring System (IBS-SSS), and fewer than 5% had mild symptoms.

Baseline assessment by the Bristol Stool Form Scale found patients had abnormal bowel movements 88% of the time, and the rate was similar across the three IBS subtypes. By week 4 the proportion had declined to 59.2% (P<0.0001), and the improvement was maintained to 12 weeks, when patients rated their bowel movements as abnormal 56.3% of the time. Significant improvements were seen in all three IBS subtypes.

The total IBS-SSS averaged 323 (severe) at baseline, decreasing to 178 (<175 = mild) by week 4, and to 144 by week 12 (P<0.0001). The total IBS QoL score improved significantly from 50.4 at baseline to 70.1 by week 4 (P<0.0001) and averaged 74.6 at week 12 (P<0.0001). Abdominal pain severity and frequency, bloating, and total gastrointestinal symptoms improved by 30-60%, irrespective of IBS subtype.

The supplement was well accepted and tolerated by the patients, said Simren. The proportion of patients who rated the product as "well tolerable" or "tolerable" ranged from 96%-98% at 4, 8, and 12 weeks. The overall adverse event rate was 15%; most common were gas, bloating, abdominal pain, diarrhea, and urgency, which was mild in 80% of cases. Eight patients discontinued the study because of side effects.

"These results are very encouraging, but they need to be validated in a randomized trial," said Simren.

In response to questions that followed his presentation, Simren said the two HMOs included in the supplement have been evaluated extensively in preclinical and clinical and are considered particularly important to gut-bowel health and function. Patients had to have stable symptoms at enrollment, and no major changes or interventions that could affect symptoms were allowed during the study. Long-term efficacy and tolerability need to be confirmed, as patients were not followed beyond the 12-week study period.

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