Heidi M. Staudacher

Fermentable Carbohydrate Restriction Reduces Luminal Bifidobacteria and Gastrointestinal Symptoms in Patients with Irritable Bowel Syndrome

Preliminary studies indicate that dietary restriction of fermentable short-chain carbohydrates improves symptoms in irritable bowel syndrome (IBS). Prebiotic fructo-oligosaccharides and galacto-oligosaccharides stimulate colonic bifidobacteria. However, the effect of restricting fermentable short-chain carbohydrates on the gastrointestinal (GI) microbiota has never been examined. This randomized controlled trial aimed to investigate the effects of fermentable carbohydrate restriction on luminal microbiota, SCFA, and GI symptoms in patients with IBS. Patients with IBS were randomized to the intervention diet or habitual diet for 4 wk. The incidence and severity of symptoms and stool output were recorded for 7 d at baseline and follow-up. A stool sample was collected and analyzed for bacterial groups using fluorescent in situ hybridization. Of 41 patients randomized, 6 were withdrawn. At follow-up, there was lower intake of total short-chain fermentable carbohydrates in the intervention group compared with controls (P = 0.001). The total luminal bacteria at follow-up did not differ between groups; however, there were lower concentrations (P < 0.001) and proportions (P < 0.001) of bifidobacteria in the intervention group compared with controls when adjusted for baseline. In the intention-to-treat analysis, more patients in the intervention group reported adequate control of symptoms (13/19, 68%) compared with controls (5/22, 23%; P = 0.005). This randomized controlled trial demonstrated a reduction in concentration and proportion of luminal bifidobacteria after 4 wk of fermentable carbohydrate restriction. Although the intervention was effective in managing IBS symptoms, the implications of its effect on the GI microbiota are still to be determined.

Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome

BACKGROUND Emerging evidence indicates that the consumption of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) may result in symptoms in some patients with irritable bowel syndrome (IBS). The present study aimed to determine whether a low FODMAP diet is effective for symptom control in patients with IBS and to compare its effects with those of standard dietary advice based on the UK National Institute for Health and Clinical Excellence (NICE) guidelines. METHODS Consecutive patients with IBS who attended a follow-up dietetic outpatient visit for dietary management of their symptoms were included. Questionnaires were completed for patients who received standard (n = 39) or low FODMAP dietary advice (n = 43). Data were recorded on symptom change and comparisons were made between groups. RESULTS In total, more patients in the low FODMAP group reported satisfaction with their symptom response (76%) compared to the standard group (54%, P = 0.038). Composite symptom score data showed better overall symptom response in the low FODMAP group (86%) compared to the standard group (49%, P < 0.001). Significantly more patients in the low FODMAP group compared to the standard group reported improvements in bloating (low FODMAP 82% versus standard 49%, P = 0.002), abdominal pain (low FODMAP 85% versus standard 61%, P = 0.023) and flatulence (low FODMAP 87% versus standard 50%, P = 0.001). CONCLUSIONS A low FODMAP diet appears to be more effective than standard dietary advice for symptom control in IBS.

Effect of short-term fat adaptation on high- intensity training

PURPOSE To determine the effect of short-term (3-d) fat adaptation on high-intensity exercise training in seven competitive endurance athletes (maximal O2 uptake 5.0 +/- 0.5 L x min(-1), mean +/-SD). METHODS Subjects consumed a standardized diet on d-0 then, in a randomized cross-over design, either 3-d of high-CHO (11 g x kg(-1)d(-1) CHO, 1 g x kg(-1) x d(-1) fat; HICHO) or an isoenergetic high-fat (2.6 g CHO x kg(-1) x d(-1), 4.6 g FAT x kg(-1) x d(-1); HIFAT) diet separated by an 18-d wash out. On the 1st (d-1) and 4th (d-4) day of each treatment, subjects completed a standardized laboratory training session consisting of a 20-min warm-up at 65% of VO2peak (232 +/- 23W) immediately followed by 8 x 5 min work bouts at 86 +/- 2% of VO2peak (323 +/- 32 W) with 60-s recovery. RESULTS Respiratory exchange ratio (mean for bouts 1, 4, and 8) was similar on d-1 for HIFAT and HICHO (0.91 +/- 0.04 vs 0.92 +/- 0.03) and on d-4 after HICHO (0.92 +/- 0.03) but fell to 0.85 +/- 0.03 (P < 0.05) on d-4 after HIFAT. Accordingly, the rate of fat oxidation increased from 31 +/- 13 on d-1 to 61 +/- 25 micromol x kg(-1) x min(-1) on d-4 after HIFAT (P < 0.05). Blood lactate concentration was similar on d-1 and d-4 of HICHO and on d-1 of HIFAT (3.5 +/- 0.9 and 3.2 +/- 1.0 vs 3.7 +/- 1.2 mM) but declined to 2.4 +/- 0.5 mM on d-4 after HIFAT (P < 0.05). Ratings of perception of effort (legs) were similar on d-1 for HIFAT and HICHO (14.8 +/- 1.5 vs 14.1 +/- 1.4) and on d-4 after HICHO (13.8 +/- 1.8) but increased to 16.0 +/- 1.3 on d-4 after HIFAT (P < 0.05). CONCLUSIONS 1) competitive endurance athletes can perform intense interval training during 3-d exposure to a high-fat diet, 2) such exercise elicited high rates of fat oxidation, but 3) compared with a high-carbohydrate diet, training sessions were associated with increased ratings of perceived exertion.

Clinical effectiveness and economic costs of group versus one‐to‐one education for short‐chain fermentable carbohydrate restriction (low FODMAP diet) in the management of irritable bowel syndrome

BACKGROUND Restriction of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) is an effective dietary treatment for irritable bowel syndrome (IBS). Patient dietary education is essential but labour intensive. Group FODMAP education may alleviate this somewhat but has not previously been investigated. The present study aimed to investigate the clinical effectiveness of low FODMAP group education in patients with IBS and to explore the cost of a group pathway. METHODS Patients with IBS (n = 364) were assessed for their suitability to attend dietitian-led group education or traditional one-to-one education in a novel group pathway. Clinical effectiveness (global symptom question, symptom prevalence, stool output) were compared at baseline and follow-up using the chi-squared test. The costs of the novel group pathway were assessed using a decision model. RESULTS The global symptom question indicated more patients were satisfied with their symptoms following dietary advice, in both group education [baseline 48/263 (18%) versus follow-up 142/263 (54%), P < 0.001] and one-to-one education [baseline 5/101 (5%) versus follow-up 61/101 (60%), P < 0.001], with no difference between group and one-to-one education at follow-up (P = 0.271). Overall, there was a significant decrease in symptom severity from baseline to follow-up (P < 0.001 for both groups) but no difference in symptom response between group and one-to-one education. The cost for the group education pathway for all 364 patients was £31 713.36. CONCLUSIONS The present study shows that dietitian-led FODMAP group education is clinically effective and the costs associated with a FODMAP group pathway are worthy of further consideration for routine clinical care.

Fructan content of commonly consumed wheat, rye and gluten-free breads

Fructans are non-digestible carbohydrates with various nutritional properties including effects on microbial metabolism, mineral absorption and satiety. They are present in a range of plant foods, with wheat being an important source. The aim of the present study was to measure the fructan content of a range of wheat, rye and gluten-free breads consumed in the United Kingdom. Fructans were measured in a range of breads using selective enzymic hydrolysis and spectrophotometry based on the AOAC 999.03 method. The breads generally contained low quantities of fructan (0.61–1.94 g/100 g), with rye bread being the richest source (1.94 g/100 g). Surprisingly, gluten-free bread contained similar quantities of fructan (1.00 g/100 g) as other breads. There was wide variation in fructan content between individual brands of granary (0.76–1.09 g/100 g) and gluten-free breads (0.36–1.79 g/100 g). Although they contain only low quantities of fructan, the widespread consumption of bread may make a significant contribution to fructan intakes.

The low FODMAP diet: recent advances in understanding its mechanisms and efficacy in IBS

There is an intensifying interest in the interaction between diet and the functional GI symptoms experienced in IBS. Recent studies have used MRI to demonstrate that short-chain fermentable carbohydrates increase small intestinal water volume and colonic gas production that, in those with visceral hypersensitivity, induces functional GI symptoms. Dietary restriction of short-chain fermentable carbohydrates (the low fermentable oligosaccharide, disaccharide, monosaccharide and polyol (FODMAP) diet) is now increasingly used in the clinical setting. Initial research evaluating the efficacy of the low FODMAP diet was limited by retrospective study design and lack of comparator groups, but more recently well-designed clinical trials have been published. There are currently at least 10 randomised controlled trials or randomised comparative trials showing the low FODMAP diet leads to clinical response in 50%–80% of patients with IBS, in particular with improvements in bloating, flatulence, diarrhoea and global symptoms. However, in conjunction with the beneficial clinical impact, recent studies have also demonstrated that the low FODMAP diet leads to profound changes in the microbiota and metabolome, the duration and clinical relevance of which are as yet unknown. This review aims to present recent advances in the understanding of the mechanisms by which the low FODMAP diet impacts on symptoms in IBS, recent evidence for its efficacy, current findings regarding the consequences of the diet on the microbiome and recommendations for areas for future research.

Altered gastrointestinal microbiota in irritable bowel syndrome and its modification by diet: probiotics, prebiotics and the low FODMAP diet

Irritable bowel syndrome (IBS) is a functional bowel disorder characterised by abdominal pain or discomfort with disordered defecation. This review describes the role of the gastrointestinal (GI) microbiota in the pathogenesis of IBS and how dietary strategies to manage symptoms impact on the microbial community. Evidence suggests a dysbiosis of the luminal and mucosal colonic microbiota in IBS, frequently characterised by a reduction in species of Bifidobacteria which has been associated with worse symptom profile. Probiotic supplementation trials suggest intentional modulation of the GI microbiota may be effective in treating IBS. A smaller number of prebiotic supplementation studies have also demonstrated effectiveness in IBS whilst increasing Bifidobacteria. In contrast, a novel method of managing IBS symptoms is the restriction of short-chain fermentable carbohydrates (low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet). Studies consistently demonstrate clinical effectiveness of the low FODMAP diet in patients with IBS. However, one unintentional consequence of this dietary intervention is its impact on the microbiota. This leads to an interesting paradox; namely, increasing luminal Bifidobacteria through probiotic supplementation is associated with a reduction in IBS symptoms while in direct conflict to this, the low FODMAP diet has clinical efficacy but markedly reduces luminal Bifidobacteria concentration. Given the multifactorial aetiology of IBS, the heterogeneity of symptoms and the complex and diverse nature of the microbiome, it is probable that both interventions are effective in patient subgroups. However combination treatment has never been explored and as such, presents an exciting opportunity for optimising clinical management, whilst preventing potentially deleterious effects on the GI microbiota.

How healthy is a gluten-free diet?

A diet that excludes the gliadin and glutenin protein fractions in wheat, rye and barley is the only treatment available for individuals with coeliac disease. There is, however, a growing enthusiasm for a gluten-free diet (GFD) or wheat avoidance in those without formally-diagnosed coeliac disease for its perceived benefit on health, weight loss, treating disease and/or minimising future risk of disease. In Australia, for example, a recent large and detailed survey of over 1000 adults indicated that almost 11 % had chosen to avoid wheat, nearly half of those being gluten-free (GF), despite a prevalence of those diagnosed with coeliac disease being much <1 %. About four out of five of those did it to help relieve symptoms such as bloating or abdominal pain. This contrasts with marketing information from USA, which suggests that most of the 30 % of the population who were considering being GF did so for ‘good health’. In a UK survey, 42 % of a cohort of patients with irritable bowel syndrome (IBS) believed they had gluten sensitivity, 15 % had tried a GFD and 12 % were still following it. With such a high proportion of the population following a restrictive diet, it is imperative that the nutritional adequacy of the diet in general and of the available GF processed foods specifically is well understood. There has been an unwritten assumption that GF alternatives are healthier than their gluten-containing counterparts. This premise may lead to overconsumption of processed/ packaged GF products including staple items (such as bread, cereals and pasta) and/or so-called energy-rich and nutrient-poor ‘discretionary’ items (such as cereal bars, biscuits and potato crisps), a scenario that appears to have been exploited by some marketers and food manufacturers. Likewise, it is often stated that GF processed and packaged foods are less healthy than their gluten-containing counterparts due to relatively higher content of fat, sugar and salt. Contemporary data on this issue are scarce, underlining the importance of the supermarket evaluation of GF foods published by Wu et al.. This Australian study was a comprehensive comparison of the nutritional quality of GF v. matched non-GF products. An impressive total of 3213 food products were assessed across ten food categories, and included staple and discretionary products. The primary outcome of the analysis was the difference in health star rating – a new front-of-pack labelling system being introduced in Australia. It rates products between 0·5 and 5 stars in increasing 0·5 star increments, with a higher star rating indicating better nutritional quality. This rating system is based on an algorithm incorporating energy, SFA, total sugar, protein, fibre and Na contents of the product. Overall, for GF staple items (pasta, bread and ready-to-eat breakfast cereals), there was no difference in mean rating for each group compared with the corresponding gluten-containing category, except for GF pasta, which scored 0·5 stars lower. On secondary analysis, the protein content of each of the three staple groups was lower in GF v. gluten-containing groups. Given the small protein contribution of grains to the overall diet, this can be considered as a negligible finding. No other differences were found between staple food groups for total energy, Na, SFA and total sugars. There were some differences in fibre content between staple groups, but dietary fibre content was not available for all products. Of importance, GF products were not consistently lower in fibre content. GF discretionary items were largely not different in star rating from their corresponding glutencontaining products, but, in fact, were rated more highly for three discretionary food groups, ice cream, maize and potato crisps and sugar-based confectioneries, largely driven by a lower mean content of SFA or total sugar. In summary, this analysis indicated that Australian GF products are not significantly different in their nutritional quality compared with their gluten-containing counterparts. This dispels the widely stated idea that GF processed foods are in general higher in fat, salt and sugar – a finding that could be interpreted as a positive outcome for many individuals with coeliac disease who regularly rely on these products. Perhaps the more important corollary of this, however, was that no nutritional advantage was demonstrated for GF foods. In other words, the notion that GF labelling might infer a health benefit is not warranted. There were certain limitations of this analysis, some of which the authors acknowledge. First, these data are based on nutrition information from the food label, rather than on the gold standard composition analysis of the food, which also prevented systematic assessment of certain important micronutrients that are often fortified in gluten-containing staple items (such as folate and Fe), and are important contributors to dietary intake (particularly fibre), but were not available on the label. Second, the primary outcome of this study was a comparison using the healthy star rating, which is not generalisable worldwide, although it is based on sound criteria. Third, only Australian-sourced products were included. Fourth, this analysis grouped foods into core food groups and analysed the nutrient content for each core group. Like-for-like analysis between foods – for example, GF v. gluten-containing white British Journal of Nutrition (2015), 114, 1539–1541

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

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.

Nutritional, microbiological and psychosocial implications of the low FODMAP diet

Dietary restriction of certain fermentable carbohydrates (low fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) diet) is effective for managing symptoms of irritable bowel syndrome (IBS). However, there are potential consequences of this diet that relate to its impact on nutritional, microbiological, and health‐related quality of life outcomes. Evidence suggests that the low FODMAP diet leads to some alterations in nutrient intake. For example, carbohydrate intake is reduced, and there is a decrease in the proportion of patients meeting the recommended intake for calcium. Intake of other macro and micro‐nutrients appears to be adequate in the short term. As well as the impact on nutrient intake, extensive dietary modification can have a pronounced impact on the gastrointestinal microbiota. Indeed, recent data suggests the diet markedly reduces luminal Bifidobacteria concentration, and there is limited evidence that it reduces total bacteria abundance and concentration of other bacterial groups, for example, Faecalibacterium prausnitzii. Finally, despite the evidence for its clinical effectiveness in patients with IBS, the restrictive nature of the diet could pose a significant burden on patients, thereby limiting improvements, or indeed worsening health‐related quality of life. In conclusion, while robust evidence supports the clinical effectiveness of the low FODMAP diet, it is important, considering the likelihood of its continued widespread use in IBS and other functional bowel disorders, that we extend our understanding of the impact of the diet on endpoints that may have potential consequences for long term health.