SAN DIEGO — Roughly half of patients who go on a low-FODMAP diet to treat diarrhea predominant irritable bowel syndrome do not respond to the change in diet. According to data presented at Digestive Disease Week, many of those patients could have a genetic variant that causes a deficiency of the sucrase-isomaltase enzyme.
Shanti L. Eswaran, MD, of the University of Michigan, said patients with this deficiency, known as SID, have trouble breaking down complex carbohydrates, including sucrose.
“Given that patients with IBS may utilize an elimination diet in order to mitigate their food-related GI symptoms, this increased risk of [sucrase-isomaltase (SI)] activity in patients with IBS-like symptoms is particularly relevant as the low-FODMAP diet does not generally exclude starch or sucrose,” she said in her presentation. “This can hold potential for the phenotyping of IBS patients and allowing for the targeting of specific dietary therapy.”
Using salivary samples taken from patients with IBS-D in a previously published trial of the low-FODMAP diet, researchers looked for SI genotype and stratified patients into groups of carriers and non-carriers of the genes. Of 46 patients who had been randomly assigned the low-FODMAP diet in the previous trial, investigators found one common and four rare hypomorphic SI variants.
In the original study, 52% of patients experienced adequate relief after switching to the low-FODMAP diet. After stratifying patients by SI variant, however, researchers found that 61% of non-carriers achieved adequate relief compared with 44% of carriers (P = .031). Patients who were not carriers of an SI variant were also more likely to experience improvement in abdominal pain compared with carriers, but the difference was not significant.
Eswaran said that their findings show that SI hypomorphic variants are associated with a significant reduction in the likelihood of responding to the low-FODMAP diet.
“Given that our current dietary treatment strategies do not take SID into account, these results may bear implications for the development of treatment stratification in IBS, getting us closer to, hopefully, precision medicine in this patient population.” - by Alex Young
Eswaran S, et al. Abstract 347. Presented at: Digestive Disease Week; May 18-21, 2019; San Diego.
Disclosures: Eswaran reports no relevant financial disclosures. Please see the meeting disclosure index for all other authors’ relevant financial disclosures.