Faecal and urine metabolites, but not gut microbiota, may predict response to low FODMAP diet in irritable bowel syndrome

BACKGROUND

The low FODMAP diet (LFD) leads to clinical response in 50%-80% of patients with irritable bowel syndrome (IBS). It is unclear why only some patients respond.

AIMS

To determine if differences in baseline faecal microbiota or faecal and urine metabolite profiles may separate clinical responders to the diet from non-responders allowing predictive algorithms to be proposed.

METHODS

We recruited adults fulfilling Rome III criteria for IBS to a blinded randomised controlled trial. Patients were randomised to sham diet with a placebo supplement (control) or LFD supplemented with either placebo (LFD) or 1.8 g/d B-galactooligosaccharide (LFD/B-GOS), for 4 weeks. Clinical response was defined as adequate symptom relief at 4 weeks after the intervention (global symptom question). Differences between responders and non-responders in faecal microbiota (FISH, 16S rRNA sequencing) and faecal (gas-liquid chromatography, gas-chromatography mass-spectrometry) and urine (1 H NMR) metabolites were analysed.

RESULTS

At 4 weeks, clinical response differed across the 3groups with adequate symptom relief of 30% (7/23) in controls, 50% (11/22) in the LFD group and 67% (16/24) in the LFD/B-GOS group (p = 0.048). In the control and the LFD/B-GOS groups, microbiota and metabolites did not separate responders from non-responders. In the LFD group, higher baseline faecal propionate (sensitivity 91%, specificity 89%) and cyclohexanecarboxylic acid esters (sensitivity 80%, specificity 78%), and urine metabolite profile (Q2 0.296 vs. randomised -0.175) predicted clinical response.

CONCLUSIONS

Baseline faecal and urine metabolites may predict response to the LFD.

Improving Food-Related Quality of Life in Inflammatory Bowel Disease through a Novel Web Resource: A Feasibility Randomised Controlled Trial

Food-related quality of life (FR-QoL) is impaired in inflammatory bowel disease (IBD) and education and support on food-related issues in IBD is needed. This feasibility trial aimed to investigate the effectiveness and acceptability of a web resource in enhancing FR-QoL in newly diagnosed IBD. Patients diagnosed with Crohn's disease or ulcerative colitis in the preceding 12 months, with an impaired FR-QoL, were recruited and randomised to either receive access to the web resource (covering IBD-specific diet concerns) or no access (control group) for 12 weeks, while receiving usual clinical care. FR-QoL, health-related quality of life, psychological outcomes, and clinical disease activity were assessed. Web resource usage was assessed, and patients' experiences of the web resource were investigated in semi-structured interviews. Of 81 patients screened, 50 participants were randomised, 30 to the web resource and 20 to control. FR-QoL increased more in the web resource (+11.7 SD 18.2) than control group (+1.4 SD 20.4) (p = 0.067), while IBD distress reduced in the web resource (-6.8 SD 26.6) and increased in the control group (+8.3 SD 25.5) (p = 0.052), albeit not statistically significantly. End of trial Crohn's disease clinical activity (PRO-2) was significantly lower in the web resource than control group (p = 0.046). Participants most frequently accessed web resource content discussing dietary management of gut symptoms and in semi-structured interviews, reported the website to contain relevant information. This feasibility study demonstrates potential effectiveness of the web resource on improving FR-QoL and psychological outcomes in IBD. An adequately powered effectiveness RCT is feasible to conduct and is now warranted. NCT03884686.

Prebiotic Galactooligosaccharide Supplementation in Adults with Ulcerative Colitis: Exploring the Impact on Peripheral Blood Gene Expression, Gut Microbiota, and Clinical Symptoms

Prebiotics may promote immune homeostasis and reduce sub-clinical inflammation in humans. This study investigated the effect of prebiotic galactooligosaccharide (GOS) supplementation in colonic inflammation. Seventeen patients with active ulcerative colitis (UC) consumed 2.8 g/d GOS for 6 weeks. At baseline and 6 weeks, gene expression (microarray), fecal calprotectin (ELISA), microbiota (16S rRNA), short-chain fatty acids (SCFAs; gas-liquid chromatography), and clinical outcomes (simple clinical colitis activity index (SCCAI), gastrointestinal symptom rating scale (GSRS), and Bristol stool form scale (BSFS)) were measured. Following prebiotics, clinical scores (SCCAI), fecal calprotectin, SCFAs, and pH were unchanged. Five genes were upregulated and two downregulated. Normal stool proportion (BSFS) increased (49% vs. 70%, p = 0.024), and the incidence (46% vs. 23%, p = 0.016) and severity (0.7 vs. 0.5, p = 0.048) of loose stool (GSRS), along with urgency (SCCAI) scores (1.0 vs. 0.5, p = 0.011), were reduced. In patients with a baseline SCCAI ≤2, prebiotics increased the relative abundance of Bifidobacterium from 1.65% (1.97) to 3.99% (5.37) (p = 0.046) and Christensenellaceae from 0.13% (0.33) to 0.31% (0.76) (p = 0.043). Prebiotics did not lower clinical scores or inflammation but normalized stools. Bifidobacterium and Christensenellaceae proportions only increased in patients with less active diseases, indicating that the prebiotic effect may depend on disease activity. A controlled study is required to validate these observations.

Effects of Low FODMAP Diet on Symptoms, Fecal Microbiome, and Markers of Inflammation in Patients With Quiescent Inflammatory Bowel Disease in a Randomized Trial

BACKGROUND & AIMS

There is limited evidence that a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) reduces gut symptoms in quiescent inflammatory bowel disease (IBD). We performed a randomized, controlled trial to investigate the effects of a low FODMAP diet on persistent gut symptoms, the intestinal microbiome, and circulating markers of inflammation in patients with quiescent IBD.

METHODS

We performed a single-blind trial of 52 patients with quiescent Crohn's disease or ulcerative colitis and persistent gut symptoms at 2 large gastroenterology clinics in the United Kingdom. Patients were randomly assigned to groups that followed a diet low in FODMAPs (n = 27) or a control diet (n = 25), with dietary advice, for 4 weeks. Gut symptoms and health-related quality of life were measured using validated questionnaires. Stool and blood samples were collected at baseline and end of trial. We assessed fecal microbiome composition and function using shotgun metagenomic sequencing and phenotypes of T cells in blood using flow cytometry.

RESULTS

A higher proportion of patients reported adequate relief of gut symptoms following the low FODMAP diet (14/27, 52%) than the control diet (4/25, 16%, P=.007). Patients had a greater reduction in irritable bowel syndrome severity scores following the low FODMAP diet (mean reduction of 67; standard error, 78) than the control diet (mean reduction of 34; standard error, 50), although this difference was not statistically significant (P = .075). Following the low FODMAP diet, patients had higher health-related quality of life scores (81.9 ± 1.2) than patients on the control diet (78.3 ± 1.2, P = .042). A targeted analysis revealed that in stool samples collected at the end of the study period, patients on the low FODMAP diet had significantly lower abundance of Bifidobacterium adolescentis, Bifidobacterium longum, and Faecalibacterium prausnitzii than patients on control diet. However, microbiome diversity and markers of inflammation did not differ significantly between groups.

CONCLUSIONS

In a trial of the low FODMAP diet vs a control diet in patients with quiescent IBD, we found no significant difference after 4 weeks in change in irritable bowel syndrome severity scores, but significant improvements in specific symptom scores and numbers reporting adequate symptom relief. The low FODMAP diet reduced fecal abundance of microbes believed to regulate the immune response, compared with the control diet, but had no significant effect on markers of inflammation. We conclude that a 4-week diet low in FODMAPs is safe and effective for managing persistent gut symptoms in patients with quiescent IBD. www.isrctn.com no.: ISRCTN17061468.

Volatile Organic Compounds in Feces Associate With Response to Dietary Intervention in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Dietary interventions are effective in management of patients with irritable bowel syndrome (IBS), although responses vary. We investigated whether fecal levels of volatile organic compounds (VOCs) associate with response to dietary interventions in patients with IBS.

METHODS

Adults who fulfilled the Rome III criteria for IBS were recruited to a 2x2 factorial randomized controlled trial. Patients were randomly assigned to a group counselled to follow a diet low in fructans, galacto-oligosaccharides, lactose, fructose, and polyols (low-FODMAP diet, n = 46) or a group that received placebo dietary advice (sham diet, n = 47) for 4 weeks. Patients from each group were also given either a multi-strain probiotic or placebo supplement. Response was defined as a reduction of 50 points or more on the validated IBS symptom scoring system. Fecal samples were collected from participants at baseline and end of the 4-week study period; VOCs were analyzed by a gas-chromatography sensor device. VOC profiles were determined using a pipeline involving wavelet transformation followed by feature selection based on random forest. A partial least squares classifier was constructed to classify VOC profiles by response and accuracies were determined using 10-fold cross-validation.

RESULTS

Data from 93 patients who completed the study (63 female) were used in the final analysis. More patients responded to the low-FODMAP diet (37/46, 80%) than the sham diet (21/47, 45%) (P < .001), but there was no difference in response between patients given the probiotic (31/49, 63%) vs the placebo (27/44, 61%) (P = .850), with no interaction between the diet and supplement interventions. At baseline, VOC profiles contained 15 features that classified response to the low-FODMAP diet with a mean accuracy of 97% (95% CI, 96%-99%) and 10 features that classified response to probiotic with a mean accuracy of 89% (95% CI, 86%-92%). End of treatment models achieved similar predictive powers and accuracies.

CONCLUSION

Fecal VOC profiling is a low cost, non-invasive tool that might be used to predict responses of patients with IBS to low-FODMAP diet and probiotics and identify their mechanisms of action. ISRCTN registry no: 02275221.

Long-term impact of the low-FODMAP diet on gastrointestinal symptoms, dietary intake, patient acceptability, and healthcare utilization in irritable bowel syndrome

BACKGROUND

The low-FODMAP diet is a frequently used treatment for irritable bowel syndrome (IBS). Most research has focused on short-term FODMAP restriction; however, guidelines recommend that high-FODMAP foods are reintroduced to individual tolerance. This study aimed to assess the long-term effectiveness of the low-FODMAP diet following FODMAP reintroduction in IBS patients.

METHODS

Patients with IBS were prospectively recruited to a questionnaire study following completion of dietitian-led low-FODMAP education. At baseline and following FODMAP restriction (short term) only, gastrointestinal symptoms were measured as part of routine clinical care. Following FODMAP reintroduction, (long term), symptoms, dietary intake, acceptability, food-related quality of life (QOL), and healthcare utilization were assessed. Data were reported for patients who continued long-term FODMAP restriction (adapted FODMAP) and/or returned to a habitual diet (habitual).

KEY RESULTS

Of 103 patients, satisfactory relief of symptoms was reported in 12% at baseline, 61% at short-term follow-up, and 57% at long-term follow-up. At long-term follow-up, 84 (82%) patients continued an 'adapted FODMAP' diet (total FODMAP intake mean 20.6, SD 14.9 g/d) compared with 19 (18%) of patients following a 'habitual' diet (29.4, SD 22.9 g/d, P=.039). Nutritional adequacy was not compromised for either group. The 'adapted FODMAP' group reported the diet cost significantly more than the 'habitual' group (P<.001) and affected social eating (P<.01) but there was no effect on food-related QOL. Healthcare utilization was similar between both groups.

CONCLUSION AND INFERENCES

Low-FODMAP education is effective for long-term IBS management, enables a nutritionally adequate diet, and is broadly acceptable to patients.

Fermentable Carbohydrates [FODMAPs] Exacerbate Functional Gastrointestinal Symptoms in Patients With Inflammatory Bowel Disease: A Randomised, Double-blind, Placebo-controlled, Cross-over, Re-challenge Trial

BACKGROUND AND AIMS

Preliminary evidence suggests that fermentable carbohydrate restriction might ameliorate functional gastrointestinal symptoms [FGS] in inflammatory bowel disease [IBD]. Our aim was to determine whether fermentable carbohydrates exacerbate FGS in IBD using a randomised, double-blinded, placebo-controlled, re-challenge trial.

METHODS

Patients with quiescent IBD and FGS responsive to a low FODMAP diet were allocated to a series of 3-day [d] fermentable carbohydrate challenges in random order [fructan, 12 g/d; galacto-oligosaccharides [GOS] 6 g/d; sorbitol, 6 g/d; and glucose placebo, 12 g/d], each separated by a washout period. Symptoms and stool output were measured daily during the challenges.

RESULTS

Thirty-two patients with IBD, fulfilling criteria for irritable bowel syndrome, functional bloating, or functional diarrhoea, were recruited and data were available for 29 patients completing all arms [12 Crohn's disease, 17 ulcerative colitis]. Significantly fewer patients reported adequate relief of FGS on the final day day of the fructan challenge [18/29, 62.1%] compared with glucose [26/29, 89.7%] [p = 0.033]. There was greater severity of pain [1.1 vs 0.5, p = 0.004], bloating [1.3 vs 0.6, p = 0.002], flatulence [1.5 vs 0.7, p = 0.004], and faecal urgency [0.9 vs 0.4, p = 0.014] on the final day of fructan challenge compared with glucose.

CONCLUSIONS

At the relatively high doses used, fructans, but not GOS or sorbitol, exacerbated FGS in quiescent IBD. Further research is required to determine whether a low FODMAP diet reduces FGS in IBD and the degree of FODMAP restriction required for symptom improvement.

Food-related Quality of Life in Inflammatory Bowel Disease: Development and Validation of a Questionnaire

BACKGROUND

Psychosocial factors surrounding eating and drinking, such as enjoying food, managing restrictions, and maintaining social relationships, remain under-researched in inflammatory bowel disease [IBD]. This study aimed to develop and validate a food-related quality of life [FR-QoL] questionnaire to systematically measure these issues in the IBD population.

METHODS

Following semi-structured interviews with 28 IBD patients, 150 potential questionnaire items were generated. These were ranked by 100 IBD patients, and items were removed based on ceiling/floor effects and high inter-item correlations [> 0.7], with 41 items being retained. In total, 323 IBD patients, 100 asthma patients [chronic disease control], and 117 healthy controls completed the FR-QoL questionnaire, alongside generic and disease-specific QoL and food satisfaction questionnaires. Principal components analysis [PCA], construct and discriminant validity, and test-retest reliability were calculated.

RESULTS

Twelve items were removed following PCA. The reduced questionnaire [FR-QoL-29] explained 63.9% of the variance [Cronbach's α = 0.96]. FR-QoL-29 correlated significantly with generic QoL [r = 0.697], depression [r = -0.519], anxiety [r = -0.531], and food satisfaction [r = 0.701]. The FR-QoL-29 sumscores were significantly lower for IBD (89.5, standard deviation [SD] 28.6) than asthma [125.4, SD 24.1; p < 0.001] and healthy volunteers [123.0, SD 16.5; p<0.001]. Within IBD, worse food-related QoL was found in those with moderate/high disease activity [66.7, SD 22.1] compared with remission/low disease activity [92.5, SD 28.1]. Test-retest reliability was good (intra-class correlation [ICC] = 0.83, 95% confidence interval [CI] = 0.76:0.88).

CONCLUSIONS

The FR-QoL-29 shows good reliability and validity across a range of IBD characteristics. This easily administered questionnaire is a useful tool in identifying poor food-related QoL and in the future may identify areas for intervention.

Pharmaceutical/food grade titanium dioxide particles are absorbed into the bloodstream of human volunteers

BACKGROUND

Exposure to persistent engineered nano and micro particles via the oral route is well established. Animal studies have demonstrated that, once ingested, a small proportion of such particles translocate from the gastrointestinal tract to other tissues. Exposure to titanium dioxide is widespread via the oral route, but only one study has provided indirect evidence (total titanium analyses) of absorption into the blood stream in humans. We sought to replicate these observations and to provide additional evidence for particulate uptake.

FINDINGS

Human volunteers with normal intestinal permeability were orally administered 100 mg pharmaceutical/food grade titanium dioxide. Blood samples were collected from 0.5 to 10 h post ingestion and analysed for the presence of reflectant bodies (particles) by dark field microscopy, and for total titanium by inductively coupled plasma mass spectrometry (ICP-MS). Blood film analyses implied early absorption of particles (2 h) with a peak maximum at 6 h following ingestion. The presence of these reflectant particles in blood roughly mirrored the levels of total titanium by ICP-MS, providing good evidence for the latter being a measure of whole particle (titanium dioxide) absorption.

CONCLUSIONS

This study shows that a fraction of pharmaceutical/food grade titanium dioxide is absorbed systemically by humans following ingestion. It confirms that at least two routes of particle uptake may exist in the human gut- one proximal and one distal. Further work should quantify human exposure and uptake of such persistent particles.

Distinct microbial populations exist in the mucosa-associated microbiota of sub-groups of irritable bowel syndrome

BACKGROUND

There is increasing evidence to support a role for the gastrointestinal microbiota in the etiology of irritable bowel syndrome (IBS). Given the evidence of an inflammatory component to IBS, the mucosa-associated microbiota potentially play a key role in its pathogenesis. The objectives were to compare the mucosa-associated microbiota between patients with diarrhea predominant IBS (IBS-D), constipation predominant IBS (IBS-C) and controls using fluorescent in situ hybridization and to correlate specific bacteria groups with individual IBS symptoms.

METHODS

Forty-seven patients with IBS (27 IBS-D and 20 IBS-C) and 26 healthy controls were recruited to the study. Snap-frozen rectal biopsies were taken at colonoscopy and bacterial quantification performed by hybridizing frozen sections with bacterial-group specific oligonucleotide probes.

KEY RESULTS

Patients with IBS had significantly greater numbers of total mucosa-associated bacteria per mm of rectal epithelium than controls [median 218 (IQR - 209) vs 128 (121) P = 0.007], and this was chiefly comprised of bacteroides IBS [69 (67) vs 14 (41) P = 0.001] and Eubacterium rectale-Clostridium coccoides [52 (58) vs 25 (35) P = 0.03]. Analysis of IBS sub-groups demonstrated that bifidobacteria were lower in the IBS-D group than in the IBS-C group and controls [24 (32) vs 54 (88) vs 32 (35) P = 0.011]. Finally, amongst patients with IBS, the maximum number of stools per day negatively correlated with the number of mucosa-associated bifidobacteria (P < 0.001) and lactobacilli (P = 0.002).

CONCLUSIONS & INFERENCES

The mucosa-associated microbiota in patients with IBS is significantly different from healthy controls with increases in bacteroides and clostridia and a reduction in bifidobacteria in patients with IBS-D.

Efficacy and tolerability of a low microparticle diet in a double blind, randomized, pilot study in Crohn's disease

BACKGROUND

Ultrafine and fine particles are potent adjuvants in antigen-mediated immune responses, and cause inflammation in susceptible individuals. Following recent findings that microparticles accumulate in the phagocytes of intestinal lymphoid aggregates, this study is the first investigation of whether their reduction in the diet improves the symptoms of Crohn's disease.

METHODS

In a double blind study, 20 patients with active corticosteroid-treated ileal or ileo-colonic Crohn's disease randomly received either a low microparticle diet (trial group; n = 10) or a control diet (n = 10) for 4 months. Crohn's disease activity index (CDAI) and corticosteroid requirements were compared.

RESULTS

One patient in each group was withdrawn. In the trial group there was a progressive decrease in CDAI from entry (392 +/- 25) to month 4 (145 +/- 47) (P = 0.002 vs control group) and seven patients were in remission (CDAI <150). In contrast, the control group had returned to baseline levels (302 +/- 28 on entry and 295 +/- 25 at month 4), with none in remission. Corticosteroid intake was reduced more in the trial group although this did not reach significance.

CONCLUSIONS

A low microparticle diet may be effective in the management of ileal Crohn's disease and could explain the efficacy of elemental diets, which similarly are low in microparticles.

Determination of titanium dioxide in foods using inductively coupled plasma optical emission spectrometry

Titanium dioxide is a common food additive of increasing interest in dietary intake studies and dietary exclusion studies. Food labelling for titanium dioxide is imprecise so a method was developed for its rapid determination in foods using acid digestion and inductively coupled plasma optical emission spectrometry (ICPOES). Twenty-five foods thought to contain titanium dioxide were obtained. Based on preliminary digestion studies, samples (500 mg) were digested in 18 mol l-1 H2SO4 at 250 degrees C for 1 h and then diluted to 5.9 mol l-1 H2SO4 before determination of titanium by ICPOES at 336.121 nm. Emission intensity was suppressed by H2SO4 so standards were matched for acid concentration. Titanium dioxide embedded in gelatine was used to assess accuracy. A standard reference material of known titanium concentration and six foods of known titanium dioxide content were used as external reference materials. Limits of detection were 2-7.5 ppb, depending on spectral integration times, and the signal was linear up to 5 ppm. Results for all control samples were in good agreement with the expected values. Twelve of the foods contained detectable titanium, ranging from 0.001 to 0.782% by weight, but only eight indicated this on their labels, four being exempt under food labelling regulations. Based on food portion sizes, an individual's daily intake of titanium dioxide could exceed 200 mg from just one of these products. This method may facilitate future studies on titanium dioxide intake, given the present limitations of food labelling.