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Background: Limited data exist to guide FODMAP (fermentable oligo‐, di‐, monosaccharides, and polyols) reintroduction to assess tolerance following a low FODMAP diet (LFD). Fructose reintroduction is often stepwise up to 7.5 g fructose (e.g., three tsp of honey). We aimed to determine the fructose tolerance threshold in non‐constipated, LFD‐responsive patients with irritable bowel syndrome (IBS) and assess whether stool microbiome predicted LFD response or fructose tolerance. Methods: Thirty‐nine non‐constipated IBS patients (51% women, mean age 33.7 years) completed a 4‐week LFD. LFD responders were defined as those who reported adequate relief of IBS symptoms following the LFD. Responders were randomized to one of the three solution groups (100% fructose, 56% fructose/44% glucose, or 100% glucose) and received four doses (2.5, 5, 10, 15 g) for 3 days each. Patients reached their tolerance dose if their mean daily IBS symptom severity (visual analog scale [VAS], 0–100 mm) was >20 mm higher than post‐LFD VAS. Stool samples before and after LFD were analyzed using shotgun metagenomics. Results: Seventy‐nine percent of patients were LFD responders. Most responders tolerated the 15 g sugar dose. There was no significant difference in mean dose tolerated between solution groups (p = 0.56). Compared to baseline, microbiome composition (beta diversity) significantly shifted and six bacterial genes in fructose and mannose metabolism pathways decreased after LFD, irrespective of LFD response or the solution group. Conclusions: Non‐constipated, LFD‐responsive IBS patients should be reintroduced to fructose in higher doses than 15 g to assess tolerance. LFD is associated with significant changes in microbial composition and bacterial genes involved in FODMAP metabolism. [ABSTRACT FROM AUTHOR]

Background: Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are chronic gastrointestinal (GI) disorders. GI symptom‐specific anxiety (GSA) is the cognitive, affective, and behavioral response stemming from fear of GI symptoms. The Visceral Sensitivity Index (VSI) measures GSA and is validated in IBS and may be useful in IBD. Methods: We compared VSI scores in IBD participants to IBS participants and healthy controls (HCs). Using validated questionnaires, we assessed the VSI's correlation with anxiety, health‐related quality of life (HRQOL), and IBD activity. Key Results: We recruited 222 age‐ and sex‐matched participants (74 IBD [23 Crohn's disease; 51 ulcerative colitis], 74 IBS, and 74 HCs). IBD and IBS participants had higher VSI scores compared with HCs (IBD = 26.62 ± 16.64, IBS = 38.83 ± 15.06; HCs = 3.42±5.06; all p's < 0.001). VSI scores were lower in IBD vs IBS (p < 0.001). In IBD, VSI modestly correlated with current anxiety (R = 0.35, p = 0.002) and the physical component of HRQOL (R = −0.45, p = 0.0001) but less with the mental component of HRQOL (R = −0.23, p = 0.05). Conclusions & Inferences: Our findings suggest the VSI is a useful measure in IBD. The VSI in IBD is related to general anxiety but is measuring a different construct and is not affected by the presence of trait anxiety. IBD patients have GSA that is associated with decreased HRQOL, which can negatively affect treatment compliance and other long‐term disease outcomes. Future studies are needed to further validate the VSI in IBD and to assess its correlation with disease activity. [ABSTRACT FROM AUTHOR]