Food Sensitivities Linked to Gut Bacteria in Irritable Bowel Syndrome

While it’s important for nutrition and an integral part of patients’ lives, food also plays a role in functional gastrointestinal disorders such as irritable bowel syndrome (IBS), and most patients already recognize some foods will cause gut symptoms when eaten.

Dietary intake affects the gastrointestinal microbiota — which is involved in the pathogenesis of functional gastrointestinal disorders — and it can be used to manage them, Kevin Whelan, PhD, a dietetics professor at King’s College London (KCL), said at Digestive Disease Week 2013, held May 18-21, 2013, in Orlando, Fla.

During his discussion of the mechanisms of food sensitivities and gut microbiota in patients with IBS, Whelan explained that more than 1,000 bacteria live in the gut, and diet is a major determinant of the roughly 160 different GI bacteria in each patient.

“Gut bacteria in people with IBS is different than in those without IBS,” Whelan noted. “Food can alter the microbiota that can affect IBS.”

Whelan indicated that taking microbiota-altering prebiotics and probiotics can improve IBS, but he cautioned that not all of those agents will produce the desired results in all patients. Before suggesting one to a patient, clinicians should research the literature to learn which agents have been shown to be effective in controlling the symptoms that the patient is experiencing, Whelan recommended.

Reporting on KCL’s research on the use of a low Fermentable, Oligo-, Di- Mono-saccharides and PolyolS (FODMAP) diet in treating IBS, Whelan said FODMAPs — which include fructans and galactans, lactose, fructose and sugar alcohols — are found in multiple foods, so while IBS patients may lack the ability to digest many FODMAPs, restricting them can be complex.

FODMAPs increase water content in the small intestine, and a high FODMAP diet produces more gas than a low FODMAP diet, Whelan said.

Whelan reported that KCL’s FODMAP service has worked with a number of patients whose bloating, pain, and diarrhea was better after following a low FODMAP diet. Those patients also consumed fewer carbohydrates, sugars, and calcium, but they maintained their fiber intake.

“A decrease can make a dramatic difference,” Whelan said, sharing data about reductions in bloating and stool frequency and an increase in normal stool consistency.

Patients may not need to restrict all FODMAPs, but it’s not always possible to know which ones can be eaten, even after breath testing. Still, Whelan said, “in the next five to 10 years, we will be in a position to do tests to determine which carbohydrates to remove from the diet.”

During the same lecture of the American Gastroenterological Association Institute, Sheila E. Crowe, MD, of the University of California, San Diego, described the role of food sensitivities and food allergies in functional gastrointestinal disorders. She reminded participants that celiac disease — which is four to five times more prevalent today than it was 50 years ago — can coexist with or mimic IBS, and the elimination of gluten, wheat, or other carbohydrates can often reduce symptoms in patients with IBS. However, few studies have demonstrated a proven benefit.

“How gluten contributes remains unclear, but multiple mechanisms are implicated,” Crowe said. “More research is needed.”