Irritable bowel syndrome (IBS), an intestinal disorder characterized by abdominal pain, bloating, and alternating episodes of diarrhea and constipation, affects as many as 14 percent of people living in the United States. Evidence suggests that people with IBS often have dysbiosis, an imbalance in the microbial makeup of the gut. A recent study indicates that human milk oligosaccharides may be beneficial in modulating the gut microbial profile of people who have IBS.

Human milk oligosaccharides (HMOs) are complex, indigestible sugars in breast milk. They serve as prebiotics – compounds that induce the growth or activity of beneficial bacteria – in the infant gut. Evidence indicates they also act as “decoys” to protect the infant from gut infections; break down biofilms that group-B streptococcus bacteria create to protect themselves from antimicrobials and antibiotics; and enhance the activity of some antibiotics by increasing the membrane permeability of pathogenic bacteria.

The phase 2, parallel, double-blind, randomized, placebo-controlled trial involved 61 adult men and women with IBS. The authors of the study assigned each participant to one of three groups, consuming a 5-gram or a 10-gram dose of an HMO product or a placebo for four weeks with a four-week follow-up period after the end of the intervention. They scored the participants' IBS symptoms using standardized symptom rating scales and assessed their overall fecal microbial composition using genome-based microbiota profiling.

None of the participants reported significant changes in their symptoms at week four or eight. However, the participants who took the 10-gram dose had higher quantities of fecal bifidobacteria at week four, but not at week eight, compared to the other groups. Higher levels of bifidobacteria are associated with health and longevity in older adults, but lower levels of bifidobacteria are associated with several chronic diseases, including IBS, inflammatory bowel diseases, and metabolic disorders.

These findings demonstrate that HMOs might be beneficial in restoring the gut microbiota of IBS patients toward a healthier profile.

• Link to study abstract.

• Learn more about HMOs in this clip in which breast milk expert Dr. Erica Sonnenburg describes the role HMOs play in establishing a healthy infant gut.