IBS and chronic idiopathic constipation (CIC) are among the most common functional gastrointestinal (GI) disorders, with studies estimating that between 5% and 15% of the general population experiences IBS symptoms, whereas CIC symptoms occur in about 14% of people. Recently, the American College of Gastroenterology (ACG) released a monograph—published in the American Journal of Gastroenterology—that updated prior monographs on approaches to treating IBS and CIC.

To develop the monograph, the ACG’s Institute for Clinical Research & Education conducted a systematic review and meta-analysis of randomized clinical trials that assessed several types of interventions for IBS and CIC. “We looked back at previous monographs from recent years,” explains Eamonn M.M. Quigley, MD, FACG, a co-author of the update. “The last monograph on constipation came out in 2005, whereas the last one on IBS was released in 2009. Since then, there have been significant developments that warranted an update.”

Diet & Fiber

An important addition to the ACG guidelines is new information on the relationship between diet and IBS (Table 1). “Research has shown that diet has emerged as a major issue, especially for patients with IBS,” says Dr. Quigley. “This isn’t new for patients because they’ve known for years about certain foods upsetting their GI tract. For clinicians, however, we now have good evidence that diet is a major factor in the precipitation of IBS attacks.”


The guidelines note that specialized diets may improve IBS symptoms for some, but the recommendation was labeled as weak because of a low quality of evidence. Current data show that gluten-free diets and diets low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols—also known as the low FODMAPs diet—are promising, but their precise role in the management of IBS needs to be better defined. “We have collected evidence supporting that certain diets appear to be helpful in managing IBS,” says Dr. Quigley. “However, more studies are needed on gluten-free diets and other diet strategies to optimize outcomes.”

Dr. Quigley says research is also needed to further explore the role of fiber in both IBS and CIC. “When managing IBS, patients need to be careful with fiber because it can actually make some cases worse,” he says. “The evidence on fiber for CIC also isn’t strong.” The guidelines note that people with CIC should slowly increase fiber intake because it may help with symptoms (Table 2). Patients with IBS should be more cautious due to potential problems with bloating.

Drug Therapy

According to the ACG monograph, some new medications have reached the market and may be helpful for managing IBS and CIC. Some of these drugs only act in the GI tract and do not need to be absorbed into the bloodstream in order to be effective. The monograph gave a strong recommendation for linaclotide as a treatment for both IBS and CIC, citing high quality of evidence for both conditions. Lubiprostone also received a strong recommendation for IBS and CIC, but the quality of evidence was characterized as moderate for IBS and high for CIC. “Both of these medications seem to be effective for each of these disorders,” Dr. Quigley says.

The evidence on prebiotics and synbiotics was classified as very low, and the ACG guidelines gave these therapies a weak recommendation for IBS. However, the writing group did note that, overall, probiotics appear to improve global symptoms, bloating, and flatulence in IBS. They also noted that probiotics generally seemed to have beneficial effects in IBS.

Other Helpful Recommendations

The ACG monograph also provides clinicians with recommendations on other more traditional treatments, including the use of antidepressants, antibiotics, serotonergic agents, and psychological therapies. “Many of these treatments can help to some extent, but some will be more helpful than others,” Dr. Quigley says. “It should be noted that many of these traditional treatments were developed before controlled clinical trials became more rigorous with regard to their performance and analysis. We don’t have a lot of high-quality evidence to support them, but these treatments may still help patients with IBS and CIC.”

Dr. Quigley anticipates that future research will garner more data on diets that may improve IBS and CIC symptoms and further establish the role of fiber for these patients. “More data are also needed on emerging drug therapies that are currently in the early phases of development,” he says. “Several treatments are being investigated for IBS and CIC and appear to be promising. As data emerge, the hope is that we’ll have more treatment options at our disposal so that we can decrease the burden of these conditions.”