Literature Review: Dietary Intervention Adherence and Adherence Barriers in Functional Gastrointestinal Disorder...

Dietary management is key in controlling functional gastrointestinal disorders (FGIDs) symptoms. However, the degree to which patients with FGIDs in clinical studies adhere to dietary recommendations is unknown. Our aim was to evaluate adherence, dietary education, and adherence-related factors in FGIDs dietary intervention trials. A literature search was performed using MEDLINE, Google Scholar, and SCOPUS for clinical trials evaluating dietary management of FGIDs. Full manuscripts published from January 2000 through August 2018 were reviewed. Data including definitions of adherence and rates, study design, dietary education, use of a dietitian, provision of study foods, potential adherence barriers, and dropouts were captured. A total of 21 publications were included. Fifteen (67%) focused on the low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) diet, 5 (24%) on fiber supplementation, and 1 (9%) on a low carbohydrate diet. Fifteen (71%) were randomized controlled trials. Meals/supplements were provided to the study participants in 27%, 80%, and 100%, of the low FODMAP, fiber, and low carbohydrate studies, respectively, which appeared to significantly enhance adherence (P<0.03). Eighteen studies (81%) provided either written or oral diet information to study participants. Overall, only 10 publications (48%) provided adherence data. Nine (60%) of the low FODMAP studies provided adherence data (range, 30% to 100%); ranges could not be calculated for the other dietary trials. The most common method to measure adherence was via food diaries. Therefore, adherence is not often measured in FGIDs dietary intervention clinical trials; when reported, rates of adherence range widely. Studies providing food had the highest adherence rates.