Summary Background  Recurrent, watery diarrhoea affects one‐third of patients diagnosed with irritable bowel syndrome (‘IBS‐D’). Idiopathic bile acid malabsorption (‘I‐BAM’) may be the cause. Aim  To determine the prevalence of I‐BAM in patients suffering from IBS‐D. Methods  A systematic search was performed of publications reporting patients presenting with IBS‐D type symptoms, who were subsequently confirmed as having I‐BAM by SeHCAT scanning. Results  Eighteen relevant studies, 15 prospective, comprising 1223 patients were identified. Five studies (429 patients) indicated that 10% (CI: 7–13) patients had severe bile acid malabsorption (SeHCAT 7 day retention <5% of baseline value). 17 studies (1073 patients) indicated that 32% (CI: 29–35) patients had moderate bile acid malabsorption (SeHCAT <10%). 7 studies (618 patients) indicated that 26% (CI: 23–30) patients had mild (SeHCAT <15%) bile acid malabsorption. Pooled data from 15 studies showed a dose‐response relationship according to severity of malabsorption to treatment with a bile acid binder: response to colestyramine occurred in 96% of patients with <5% retention, 80% at <10% retention and 70% at <15% retention. Conclusions  Idiopathic adult‐onset bile acid malabsorption is not rare. International guidelines for the management of irritable bowel syndrome need to be revised so that clinicians become more aware of this possibility.

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There is limited weak evidence for the efficacy of fiber in improving disease outcomes in UC and pouchitis. The potential antiinflammatory role of fiber is intriguing and merits further investigation in adequately powered clinical trials. Excluding overt gastrointestinal obstruction, there was no evidence that fiber intake should be restricted in patients with inflammatory bowel disease.

Background: Therapeutic radiotherapy is an important treatment of pelvic cancers. Historically, low-fiber diets have been recommended despite a lack of evidence and potentially beneficial mechanisms of fiber.Objective: This randomized controlled trial compared low-, habitual-, and high-fiber diets for the prevention of gastrointestinal toxicity in patients undergoing pelvic radiotherapy. Design: Patients were randomly assigned to low-fiber [#10 g nonstarch polysaccharide (NSP)/d], habitual-fiber (control), or high-fiber ($18 g NSP/d) diets and received individualized counseling at the start of radiotherapy to achieve these targets. The primary endpoint was the difference between groups in the change in the Inflammatory Bowel Disease QuestionnaireBowel Subset (IBDQ-B) score between the starting and nadir (worst) score during treatment. Other measures included macronutrient intake, stool diaries, and fecal short-chain fatty acid concentrations. Results: Patients were randomly assigned to low-fiber (n = 55), habitual-fiber (n = 55), or high-fiber (n = 56) dietary advice. Fiber intakes were significantly different between groups (P , 0.001). The difference between groups in the change in IBDQ-B scores between the start and nadir was not significant (P = 0.093). However, the change in score between the start and end of radiotherapy was smaller in the high-fiber group (mean 6 SD: 23.7 6 12.8) than in the habitual-fiber group (210.8 6 13.5; P = 0.011). At 1-y postradiotherapy (n = 126) the difference in IBDQ-B scores between the high-fiber (+0.1 6 14.5) and the habitualfiber (28.4 6 13.3) groups was significant (P = 0.004). No significant differences were observed in stool frequency or form or in short-chain fatty acid concentrations. Significant reductions in energy, protein, and fat intake occurred in the low-and habitualfiber groups only. Conclusions: Dietary advice to follow a high-fiber diet during pelvic radiotherapy resulted in reduced gastrointestinal toxicity both acutely and at 1 y compared with habitual-fiber intake. Restrictive, non-evidence-based advice to reduce fiber intake in this setting should be abandoned. This trial was registered at clinicaltrials.gov as NCT 01170299.Am J Clin Nutr doi: https://doi.org/10.3945/ajcn.116.150565.

Conformal radiotherapy techniques are an improvement on older radiotherapy techniques. IMRT may be better than 3DCRT in terms of GI toxicity, but the evidence to support this is uncertain. There is no high-quality evidence to support the use of any other prophylactic intervention evaluated. However, evidence on some potential interventions shows that they probably have no role to play in reducing RT-related GI toxicity. More RCTs are needed for interventions with limited evidence suggesting potential benefits.

How to cite this article: Wedlake L.J., McGough C., Shaw C., Klopper T., Thomas K., Lalji A., Dearnaley D.P., Blake P., Tait D., Khoo V.S. & Andreyev H.J.N. (2012) Clinical trial: efficacy of a low or modified fat diet for the prevention of gastrointestinal toxicity in patients receiving radiotherapy treatment for pelvic malignancies. J Hum Nutr Diet.25, 247–259 Abstract Background:  Inflammatory responses to pelvic radiotherapy can result in severe changes to normal gastrointestinal function with potentially severe long‐term effects. Reduced or modified fat diets may confer benefit. Methods:  This randomised controlled trial recruited patients with gynaecological, urological or lower gastrointestinal malignancy due to receive radical radiotherapy. Patients were randomised to a low fat (20% total energy from long chain triglycerides), modified fat (20% from long chain triglycerides and 20% from medium chain triglycerides) or normal fat diet (40% total energy from long chain triglycerides). The primary outcome was a difference in change in Inflammatory Bowel Disease Questionnaire – Bowel (IBDQ‐B) score, from the start to end of radiotherapy. Results:  A total of 117 patients with pelvic tumours (48% urological; 32% gastrointestinal; 20% gynaecological), with mean (SD) age: 65 (11.0) years, male : female ratio: 79 : 38, were randomised. The mean (SE) fall in paired IBDQ‐B score was −7.3 (0.9) points, indicating a worsening toxicity. Differences between groups were not significant: P = 0.914 (low versus modified fat), P = 0.793 (low versus normal fat) and P = 0.890 (modified versus normal fat). The difference in fat intake between low and normal fat groups was 29.5 g [1109 kJ (265 kcal)] amounting to 11% (of total energy intake) compared to the planned 20% differential. Full compliance with fat prescription was only 9% in the normal fat group compared to 93% in the low fat group. Conclusions:  A low or modified fat diet during pelvic radiotherapy did not improve gastrointestinal symptom scores compared to a normal fat intake. An inadequate differential in fat intake between the groups may have confounded the results.

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