The Impact of a 4-Week Low-FODMAP and mNICE Diet on Nutrient Intake in a Sample of US Adults with Irritable Bowel Syndrome with Diarrhea

Abstract

Background: A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) has gained increasing acceptance for the treatment of irritable bowel syndrome but safety concerns have been raised regarding nutritional adequacy. Changes in nutrient intake during the elimination phase of the low-FODMAP diet remain predominantly unknown.

Objective: To determine changes in the mean reported daily nutrient content before and after 4 weeks of a low-FODMAP diet vs modified National Institute for Health and Clinical Excellence (mNICE) dietary intervention and to identify nutritional inadequacies based on comparison to the Dietary Reference Intakes in patients with irritable bowel syndrome-diarrhea subtype.

Design: Post hoc analysis of a randomized controlled trial entailing a 4-week trial period comparing the low-FODMAP and mNICE diets.

Participants and setting: A total of 78 patients (41 low FODMAP and 37 mNICE) meeting the Rome III criteria for irritable bowel syndrome-diarrhea subtype were consecutively recruited from gastroenterology and primary care clinics at the University of Michigan Medical Center between October 2012 and November 2015.

Methods: Participants randomized to the low-FODMAP arm were instructed to decrease their dietary intake of FODMAPs, whereas participants randomized to the mNICE intervention arm were instructed to eat small frequent meals, avoid trigger foods, and avoid excess alcohol and caffeine.

Main outcome measures: Post hoc evaluation for presence of micronutrient deficiencies per Dietary Reference Intakes when implementing low-FODMAP vs mNICE dietary interventions. Dietary intake was analyzed via 3-day food diaries at baseline and during the final week of the assigned diet.

Statistical analyses performed: A post hoc analysis utilizing either a t test or χ² analysis was conducted between before and after data.

Results: Both diets resulted in fewer daily kilocalories consumed, fewer number of daily meals consumed, and less daily carbohydrate intake. Among the patients following the low-FODMAP diet, there was a statistically significant decrease from baseline in several micronutrients, which was not observed in the mNICE cohort. However, these differences in the low-FODMAP group remained significant only for riboflavin after correcting for calorie-adjusted nutrient intake. Comparing Dietary Reference Intakes of participants pre- and postintervention, fewer patients met the Dietary Reference Intakes for thiamin and iron in the low FODMAP group, and for calcium and copper in the mNICE group.

Conclusions: During a 4-week dietary intervention, the mean daily intake of most micronutrients remained stable and within the Recommended Dietary Allowances for both diets. Although decrease in several micronutrients was observed with implementation of the low-FODMAP diet relative to the mNICE diet, most of these disappeared after adjusting for energy intake.

Keywords: Dietary intervention; Functional disorder; Micronutrient; Nutrition.