Table 3.

Observational studies of low FODMAP diet in adults with IBS

Study	Study design	Participants recruited for the study	Inclusion and exclusion criteria	Dietary intervention	Outcome measures	Key results
Observational studies
Shepherd and Gibson48	Retrospective study Follow-up telephone interview 2–40 months after dietary intervention (median 14 months)	62 consecutive patients with IBS and fructose malabsorption Median age 50 years 76% female	IBS (Rome II criteria) Positive fructose breath hydrogen test. Excluded celiac disease, IBD, and patients with known lactose malabsorption	1-hour dietitian-delivered advice: • avoidance of high free fructose foods in excess of glucose and high fructan foods • positive food choices • sample meal plan • coingestion of free glucose with fructose • avoiding foods rich in polyols	Dietary adherence Barriers to adherence Strategies used by patients Self-assessment of IBS symptoms using a –10 to 10 scale	48 (77%) adhered to the diet 46 (74%) responded positively in all abdominal symptoms Improvement in symptoms was significantly better in those adherent to the diet
Staudacher et al54	Nonrandomized, controlled study Questionnaire 2–6 months after dietary manipulation	82 consecutive patients with IBS Mean age 38 years 71% female	IBS diagnosis based on NICE criteria	Dietitian-led advice 39 – standard dietary advice (NICE guidelines) 43 – low FODMAP dietary advice: • suitable/unsuitable foods • meal plans • recipes adapted for the UK setting	Validated IBS Global Improvement Scale (7-point Likert scale) Four statements on satisfaction with symptom response and dietary advice	Overall symptom improvement greater in low FODMAP (86%) than standard diet (49%) group Greater benefits were seen in low FODMAP group for bloating, abdominal pain, and flatulence
Ostgaard et al49	Retrospective, case-control study Dietary guidance was given 2 years before the study Questionnaires sent by mail	63 patients with IBS without dietary guidance, 70 with dietary guidance, and 42 healthy controls Mean age 36 years 85% female	IBS diagnosis (Rome III criteria) Excluded organic GI disease, clinically significant systemic diseases, pregnant or lactating women, and abdominal surgeries, except appendectomy, Cesarean, and hysterectomy	Nurse-delivered dietary advice Two 1-hour sessions covering FODMAP avoidance	Validated MoBa FFQ SF-NDI IBS-QoL Validated Birmingham IBS Symptom scores (5-point Likert scale)	114 patients (65%) completed study (35 controls, 36 unguided, 43 guided patients with IBS) In guided patients with IBS, significant reduction in abdominal pain, but no significant differences in the total score or diarrhea/constipation Significant QoL improvement of guided patients with IBS compared to unguided patients
Mazzawi et al50	Prospective uncontrolled study Questionnaires before and 3–9 months after dietary intervention (median 4 months)	46 patients with IBS Mean age 35 years 76% female	IBS (Rome III criteria) Excluded organic GI disease, clinically significant systemic disease, pregnant or lactating, drug abuse, serious psychiatric diseases, abdominal surgeries, except appendectomy, cesarean section, and hysterectomy	Registered nurse with special training and experience. Three 45-minute sessions on dietary management	Validated Birmingham IBS symptom score IBS-QoL questionnaire SF-NDI Validated MoBa FFQ	17 (37%) completed study Reduced total IBS symptoms scores and significantly improved quality life following dietary guidance Significant improvement in abdominal pain, diarrhea, but not constipation Dietary guidance also resulted in adequate intakes of vitamins and minerals
de Roest et al51	Prospective uncontrolled study Questionnaires at baseline and follow-up (mean follow-up of 15.7±9 months) after dietary intervention	192 patients with IBS who had performed lactulose, fructose, and lactose breath testing Mean age 45 years 74% female	IBS diagnosed by a gastroenterologist or a colorectal surgeon Excluded significant GI comorbidities (IBD, celiac disease, significant diverticular disease or bowel resection)	Advice by a trained dietitian: • 1 -hour appointment and 30-minute follow-up 6 weeks later • lists of safe and restricted foods • recipes and shopping guide provided • reintroduction of restricted group of carbohydrates at follow-up	GSRS (7-point Likert scale) Assessment of safety and efficacy of the diet by email or post	90 patients with IBS (47%) completed the whole study. Significant improvement reported symptoms at follow-up (44% patients with improvement in abdominal pain, 38% in bloating, 38.5% in constipation, 60% in diarrhea) Significant positive correlation between adherence and improvement in individual GI symptoms
Wilder-Smithet al53	Prospective, uncontrolled study Questionnaires at baseline and 4 weeks after dietary intervention	1,372 patients with FGID (212 patients with IBS) who performed fructose and lactose breath testing Mean age 42 years 73% female	Classified into FGID subgroups according to (Rome III) 312 patients with positive fructose and lactose intolerance Excluded organic disease including celiac disease	Experienced dietitian-led advice: • standardized 4-week dietary modification • 1 week of diet low in saccharides and polyols followed by weekly introduction of fructose-, fructan-, inulin-, and lactose- containing food to individual tolerance	A nonstandard questionnaire on abdominal symptoms (10-point Likert scales) Bowel and dietary habits	237 of 312 (76%) patients completed the study Over 80% of patients attained adequate global symptom relief; 93% and 96% of patients with fructose or lactose malabsorption, respectively, 85% adequate relief in patients with diarrhea, 96% with bloating, and 51% with constipation
Pedersen et al52	Prospective uncontrolled pilot study Web-based questionnaires completed weekly during control and low FODMAP diet period (6 weeks each)	19 patients with IBS Median age 35 years 81% female	IBS (Rome III criteria) Excluded IBD, celiac disease, GI infection, and positive lactose intolerance gene test, history of food allergy, alarm symptoms, and other significant diseases	6 weeks of habitual diet (control) Dietitian-delivered low FODMAP diet: • 45-minute consultation • 6 weeks on the diet	IBS-SSS IBS-QoL	All 19 patients with IBS completed the study Significant improvement in IBS in control period and following dietary intervention period Low FODMAP diet further reduced symptoms (11 patients [57%] improved to mild IBS severity) Significant IBS-QoL change during low FODMAP diet period

Abbreviations: FODMAP, fermentable oligosaccharide, disaccharide, monosaccharide, and polyols; IBS, irritable bowel syndrome; FM, fructose malabsorption; IBD, inflammatory bowel disease; NICE, National Institute for Health and Clinical Excellence; MoBa FFQ, MoBa Food Frequency Questionnaire; SF-NDI, short-form nepean dyspepsia index; QoL, quality of life; IBS-SSS, irritable bowel syndrome symptom scoring system; GSRS, gastrointestinal symptom rating scale; GI, gastrointestinal; FGID, functional gastrointestinal disorder; ITT, intention to treat; PP, per-protocol.