Comparison of breath testing with fructose and high fructose corn syrups in health and IBS

Fructose malabsorption and fructan malabsorption are associated in patients with irritable bowel syndrome

BACKGROUND

Food malabsorption and intolerance is implicated in gastrointestinal symptoms among patients with irritable bowel syndrome (IBS). Key triggers include fructose and fructan. Prior studies examined fructose and fructan malabsorption separately in IBS patients. None have concurrently assessed both within the same patient group. We aimed to investigate the association between fructose and fructan malabsorption in the same patients with IBS using hydrogen breath testing (HBT).

METHODS

We retrospectively identified patients with IBS who underwent fructose and fructan HBTs and abstracted their results from the electronic medical record. Fructose and fructan HBTs were performed by administering a 25 g fructose solution or 10 g fructan solution, followed by breath hydrogen readings every 30 min for 3 h. Patients were positive for fructose or fructan malabsorption if breath hydrogen levels exceeded 20 ppm.

RESULTS

Of 186 IBS patients, 71 (38.2%) were positive for fructose malabsorption and 91 (48.9%) were positive for fructan malabsorption. Of these patients, 42 (22.6%) were positive for fructose malabsorption and fructan malabsorption. Positive fructose HBT readings were significantly associated with positive fructan HBT readings (p = 0.0283). Patients positive for fructose malabsorption or fructan malabsorption had 1.951 times higher odds of testing positive for the other carbohydrate.

CONCLUSIONS

Our results reveal a clinically significant association between fructose malabsorption and fructan malabsorption in patients with IBS. Fructan malabsorption should be assessed in patients with fructose malabsorption, and vice versa. Further studies are required to identify the mechanisms underlying our findings.

Dietary compounds in modulation of gut microbiota-derived metabolites

Gut microbiota, a group of microorganisms that live in the gastrointestinal tract, plays important roles in health and disease. One mechanism that gut microbiota in modulation of the functions of hosts is achieved through synthesizing and releasing a series of metabolites such as short-chain fatty acids. In recent years, increasing evidence has indicated that dietary compounds can interact with gut microbiota. On one hand, dietary compounds can modulate the composition and function of gut microbiota; on the other hand, gut microbiota can metabolize the dietary compounds. Although there are several reviews on gut microbiota and diets, there is no focused review on the effects of dietary compounds on gut microbiota-derived metabolites. In this review, we first briefly discussed the types of gut microbiota metabolites, their origins, and the reasons that dietary compounds can interact with gut microbiota. Then, focusing on gut microbiota-derived compounds, we discussed the effects of dietary compounds on gut microbiota-derived compounds and the following effects on health. Furthermore, we give our perspectives on the research direction of the related research fields. Understanding the roles of dietary compounds on gut microbiota-derived metabolites will expand our knowledge of how diets affect the host health and disease, thus eventually enable the personalized diets and nutrients.

Highly Sensitive and Selective Detection of Hydrogen Using Pd-Coated SnO2 Nanorod Arrays for Breath-Analyzer Applications

We report a breath hydrogen analyzer based on Pd-coated SnO₂ nanorods (Pd-SnO₂ NRs) sensor integrated into a miniaturized gas chromatography (GC) column. The device can measure a wide range of hydrogen (1–100 ppm), within 100 s, using a small volume of human breath (1 mL) without pre-concentration. Especially, the mini-GC integrated with Pd-SnO₂ NRs can detect 1 ppm of H₂, as a lower detection limit, at a low operating temperature of 152 °C. Furthermore, when the breath hydrogen analyzer was exposed to a mixture of interfering gases, such as carbon dioxide, nitrogen, methane, and acetone, it was found to be capable of selectively detecting only H₂. We found that the Pd-SnO₂ NRs were superior to other semiconducting metal oxides that lack selectivity in H₂ detection. Our study reveals that the Pd-SnO₂ NRs integrated into the mini-GC device can be utilized in breath hydrogen analyzers to rapidly and accurately detect hydrogen due to its high selectivity and sensitivity.

Overview of Breath Testing in Clinical Practice in North America

Human breath is an easily, noninvasively obtained substance. It offers insight into metabolism and is used to diagnose disaccharide malabsorption, infection, small bowel bacterial over growth, and transit times. Herein, we discuss the readily available clinical breath tests, how they function, how they are administered and interpreted and some pitfalls in their use.

Habitual FODMAP Intake in Relation to Symptom Severity and Pattern in Patients with Irritable Bowel Syndrome

Restricting intake of FODMAPs (Fermentable Oligo-, Di-, Monosaccharides and Polyols) is used as treatment for irritable bowel syndrome (IBS). However, whether habitual FODMAP consumption correlates to symptom severity, and if this relationship differs among IBS subtypes, is unclear. The aim was to study the relationship between habitual FODMAP intake and symptom severity. A total of 189 patients with IBS—IBS with constipation (IBS-C) n = 44 (22.3%), IBS with diarrhea (IBS-D) n = 54 (27.4%), mixed IBS (IBS-M) n = 46 (23.4%) and unsubtyped IBS (IBS-U) n = 46 (23.4%)—recorded food intake during four days. Symptom severity was measured with the IBS severity scoring system (IBS-SSS). For FODMAP intake, a lower lactose intake was noted among women with IBS-D, p = 0.009. In women, there was a statistically significant relationship between energy-adjusted FODMAP intake and IBS-SSS (r = 0.21, p = 0.003). This was mainly driven by the subtype IBS-U, where excess fructose intake accounted for 19.9% of explained variance in IBS-SSS (p = 0.007). This study demonstrates small differences in FODMAP intake among IBS patients with different subtypes. Association between IBS symptoms and FODMAP intake was most prominent in unsubtyped IBS. However, patients who are intolerant to certain FODMAPs may already have reduced their FODMAP intake, and this warrants future cohort or experimental studies to uncover.

Changes in gut microbial metagenomic pathways associated with clinical outcomes after the elimination of malabsorbed sugars in an IBS cohort

Specific diets to manage sugar malabsorption are reported to reduce clinical symptoms of irritable bowel syndrome (IBS). However, the effects of diets for malabsorbed sugars on gut microbiota signatures have not been studied, and associations with clinical outcomes in IBS have not been characterized. 22 IBS patients positively tested for either lactose-, fructose-, sorbitol- or combined malabsorptions were subjected to 2-weeks sugar elimination and subsequent 4-weeks re-introduction. 7 IBS patients tested negative for sugar malabsorption were used as controls. Nutrition and clinical symptoms were recorded throughout the study. Fecal samples were serially collected for 16S rRNA amplicon and shotgun-metagenome sequencing. Dietary intervention supervised by nutrition counseling reduced IBS symptoms during the elimination and tolerance phases. Varying clinical response rates were observed between subjects, and used to dichotomize our cohort into visual analogue scale (VAS) responders and non-responders. Alpha -and beta-diversity analyzes revealed only minor differences regarding 16S rRNA-based fecal microbiota compositions between responder and non-responder patients during baseline or tolerance phase. In shotgun-metagenome analyzes, however, we analyzed microbial metabolic pathways and found significant differences in pathways encoding starch degradation and complex amino acid biosynthesis at baseline between IBS controls and malabsorbers, and notably, between diet responder and non-responders. Faecalibacterium prausnitzii, Ruminococcus spp. and Bifidobacterium longum largely informed these metabolic pathways. Our study demonstrates that diet interventions for specific, malabsorbed carbohydrates reshaped the metagenomic composition of the gut microbiota, with a small community of bacterial taxa contributing to these changes rather than a single species.

Fructose and irritable bowel syndrome

Irritable bowel syndrome (IBS) is a chronic disorder characterised by recurrent abdominal pain or discomfort and transit disturbances with heterogeneous pathophysiological mechanisms. The link between food and gastrointestinal (GI) symptoms is often reported by patients with IBS and the role of fructose has recently been highlighted. Fructose malabsorption can easily be assessed by hydrogen and/or methane breath test in response to 25 g fructose; and its prevalence is about 22 % in patients with IBS. The mechanism of fructose-related symptoms is incompletely understood. Osmotic load, fermentation and visceral hypersensitivity are likely to participate in GI symptoms in the IBS population and may be triggered or worsened by fructose. A low-fructose diet could be integrated in the overall treatment strategy, but its role and implication in the improvement of IBS symptoms should be evaluated. In the present review, we discuss fructose malabsorption in adult patients with IBS and the interest of a low-fructose diet in order to underline the important role of fructose in IBS.

Intestinal gases: influence on gut disorders and the role of dietary manipulations

The inner workings of the intestines, in which the body and microbiome intersect to influence gut function and systemic health, remain elusive. Carbon dioxide, hydrogen, methane and hydrogen sulfide, as well as a variety of trace gases, are generated by the chemical interactions and microbiota within the gut. Profiling of these intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. Indeed, different tools for measuring these intestinal gases have been developed, including newly developed gas-sensing capsule technology. Gases can, according to their type, concentration and volume, induce or relieve abdominal symptoms, and might also have physiological, pathogenic and therapeutic effects. Thus, profiling and modulating intestinal gases could be powerful tools for disease prevention and/or therapy. As the interactions between the microbiota, chemical constituents and fermentative substrates of the gut are principally influenced by dietary intake, altering the diet, which, in turn, changes gas profiles, is the main therapeutic approach for gastrointestinal disorders. An improved understanding of the complex interactions within the intestines that generate gases will enhance our ability to prevent, diagnose, treat and monitor many gastrointestinal disorders.

Review article: biological mechanisms for symptom causation by individual FODMAP subgroups - the case for a more personalised approach to dietary restriction

BACKGROUND

Due to the paucity of targeted therapy for irritable bowel syndrome (IBS), many patients turn to dietary modifications for symptom management. The combination of five subgroups of poorly absorbed and rapidly fermented carbohydrates-fructans, galacto-oligosaccharides, lactose, excess fructose and polyols-are thought to trigger gastrointestinal symptoms and are referred to collectively as "FODMAPs".

AIMS

To examine the biological plausibility and mechanisms by which foods high in specific FODMAP subgroups cause symptoms, and to use this information to explore the possibility of targeting select dietary components to allow for a more personalised approach to dietary adjustment METHODS: Recent literature was analysed via search databases including Medline, PubMed and Scopus.

RESULTS

Lactose, fructans and galacto-oligosaccharides have strong biologic plausibility for symptom generation due to lack of hydrolases resulting in distention from osmosis and rapid fermentation. However, excess fructose and polyols may only cause symptoms in specific individuals when consumed in high doses, but this remains to be established. There is evidence to suggest that certain patient characteristics such as ethnicity may predict response to lactose, but differentiation of other subgroups is difficult prior to dietary manipulation.

CONCLUSIONS

While some clear mechanisms of action for symptom generation have been established, further research is needed to understand which patients will respond to specific FODMAP subgroup restriction. We suggest that clinicians consider in some patients a tailored, personalised "bottom-up" approach to the low-FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile and usual dietary intake.

Prevalence of Fructose Malabsorption in Patients With Irritable Bowel Syndrome After Excluding Small Intestinal Bacterial Overgrowth

Background/Aims

Fructose malabsorption (FM) mimics symptoms of irritable bowel syndrome (IBS), and its prevalence has increased. Diagnosing FM in IBS is challenging because of its overlap with small intestinal bacterial overgrowth (SIBO). We assessed the prevalence of FM by comparing patients with IBS with asymptomatic control individuals after excluding SIBO using the glucose hydrogen breath test (HBT).

Methods

Patients diagnosed with IBS and asymptomatic control individuals were enrolled prospectively. Dietary habits were assessed with the Food Frequency Questionnaire. After excluding SIBO, participants underwent HBTs with both 15 g and 25 g of fructose.

Results

Thirty-five patients with IBS and 35 age- and sex-matched asymptomatic control individuals were enrolled. The 15-g fructose HBT yielded positive results in 7 of the 35 (20.0%) patients with IBS and in 2 of 35 (5.7%) controls (P = 0.070). The 25-g fructose HBT was positive in 16 of the 35 (45.7%) patients with IBS and in 8 of the 35 (22.9%) controls (P = 0.040). Analysis of the Food Frequency Questionnaire responses showed no significant differences between the 2 groups in dietary intake, although patients with IBS showed a significantly higher mean fiber intake than controls (21.24 ± 11.35 g vs 15.87 ± 7.07 g, respectively, P = 0.040).

Conclusions

The 25-g fructose HBT identified FM in a significantly higher percentage of SIBO-negative patients with IBS than in asymptomatic control individuals, suggesting that FM may correlate with IBS. Education regarding dietary control of foods containing fructose may be useful for the management of patients with IBS.

Nutrition in the management of gastrointestinal diseases and disorders: the evidence for the low FODMAP diet

A growing interest from both physicians and patients is fueling research in the interaction of symptoms related to irritable bowel syndrome (IBS) and diet, particularly the low FODMAP diet. Recent studies further define the role of these short-chain fermentable carbohydrates on IBS symptoms and their effects in different parts of the gastrointestinal tract. Mounting evidence supports the use of a low FODMAP diet in the clinical setting, but this dietary approach is not without potential drawbacks. This review illustrates the mechanisms by which the low FODMAP diet leads to improvement in IBS symptoms, summarizes the available clinical evidence, and offers practical advice regarding implementation of this dietary strategy.

Irritable Bowel Syndrome: Clinical Manifestations, Dietary Influences, and Management

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder that is characterized by symptoms of chronic abdominal pain and altered bowel habits in the absence of an overtly identifiable cause. It is the most commonly diagnosed functional gastrointestinal disorder, accounting for about one third of gastroenterology visits. It generally presents as a complex of symptoms, including psychological dysfunction. Hypersensitivity to certain foods, especially foods that contain high amounts of fructose, plays a role in the pathophysiology of IBS. Elevated consumption of high-fructose corn syrup (HFCS) has been discussed in this aspect. The treatment options for IBS are challenging and varied. In addition to dietary restrictions for HFCS-induced IBS, such as low-FODMAP (Fermentable Oligosaccharides, Disaccharide, Monosaccharides, and Polyols) diets, existing drug therapies are administered based on the predominant symptoms and IBS-subtype. Patients with IBS are likely to suffer from issues, such as anxiety, depression, and post-traumatic-stress disorder. Biopsychosocial factors particularly socioeconomic status, sex, and race should, thus, be considered for diagnostic evaluation of patients with IBS.

Colon Hypersensitivity to Distension, Rather Than Excessive Gas Production, Produces Carbohydrate-Related Symptoms in Individuals With Irritable Bowel Syndrome

BACKGROUND & AIMS

Poorly digested, fermentable carbohydrates may induce symptoms of irritable bowel syndrome (IBS) via unclear mechanisms. We performed a randomized trial with magnetic resonance imaging (MRI) analysis to investigate correlations between symptoms and changes in small- and large-bowel contents after oral challenge.

METHODS

We performed a 3-period, cross-over study of 29 adult patients with IBS (based on Rome III criteria, with symptoms of abdominal pain or discomfort for at least 2 days/wk) and reported bloating. In parallel, we performed the same study of 29 healthy individuals (controls). Studies were performed in the United Kingdom from January 2013 through February 2015. On 3 separate occasions (at least 7 days apart), subjects were given a 500-mL drink containing 40 g of carbohydrate (glucose in the first period, fructose in the second, and inulin in the third, in a random order). Levels of breath hydrogen were measured and intestinal content was assessed by MRI before and at various time points after consumption of each drink. Symptoms were determined based on subjects' responses to the Hospital Anxiety and Depression Scale questionnaire and the Patient Health Questionnaire-15. The primary end point was whether participants had a clinically important symptom response during the 300 minutes after consumption of the drink.

RESULTS

More patients with IBS reached the predefined symptom threshold after intake of inulin (13 of 29) or fructose (11 of 29) than glucose (6 of 29). Symptoms peaked sooner after intake of fructose than inulin. Fructose increased small-bowel water content in both patients and controls whereas inulin increased colonic volume and gas in both. Fructose and inulin increased breath hydrogen levels in both groups, compared with glucose; fructose produced an earlier increase than inulin. Controls had lower symptom scores during the period after drink consumption than patients with IBS, despite similar MRI parameters and breath hydrogen responses. In patients who reached the symptom threshold after inulin intake, peak symptom intensity correlated with peak colonic gas (r = 0.57; P < .05). Changes in MRI features and peak breath hydrogen levels were similar in patients who did and did not reach the symptom threshold.

CONCLUSIONS

Patients with IBS and healthy individuals without IBS (controls) have similar physiological responses after intake of fructose or inulin; patients reported symptoms more frequently after inulin than controls. In patients with a response to inulin, symptoms related to levels of intraluminal gas, but peak gas levels did not differ significantly between responders, nonresponders, or controls. This indicates that colonic hypersensitivity to distension, rather than excessive gas production, produces carbohydrate-related symptoms in patients with IBS. Clinicaltrials.gov no: NCT01776853.

Adding glucose to food and solutions to enhance fructose absorption is not effective in preventing fructose-induced functional gastrointestinal symptoms: randomised controlled trials in patients with fructose malabsorption

BACKGROUND

In healthy individuals, the absorption of fructose in excess of glucose in solution is enhanced by the addition of glucose. The present study aimed to assess the effects of glucose addition to fructose or fructans on absorption patterns and genesis of gastrointestinal symptoms in patients with functional bowel disorders.

METHODS

Randomised, blinded, cross-over studies were performed in healthy subjects and functional bowel disorder patients with fructose malabsorption. The area-under-the-curve (AUC) was determined for breath hydrogen and symptom responses to: (i) six sugar solutions (fructose in solution) (glucose; sucrose; fructose; fructose + glucose; fructan; fructan + glucose) and (ii) whole foods (fructose in foods) containing fructose in excess of glucose given with and without additional glucose. Intake of fermentable short chain carbohydrates (FODMAPs; fermentable, oligo-, di-, monosaccharides and polyols) was controlled.

RESULTS

For the fructose in solution study, in 26 patients with functional bowel disorders, breath hydrogen was reduced after glucose was added to fructose compared to fructose alone [mean (SD) AUC 92 (107) versus 859 (980) ppm 4 h^-1 , respectively; P = 0.034). Glucose had no effect on breath hydrogen response to fructans (P = 1.000). The six healthy controls showed breath hydrogen patterns similar to those with functional bowel disorders. No differences in symptoms were experienced with the addition of glucose, except more nausea when glucose was added to fructose (P = 0.049). In the fructose in foods study, glucose addition to whole foods containing fructose in excess of glucose in nine patients with functional bowel disorders and nine healthy controls had no significant effect on breath hydrogen production or symptom response.

CONCLUSIONS

The absence of a favourable response on symptoms does not support the concomitant intake of glucose with foods high in either fructose or fructans in patients with functional bowel disorders.

Effects of dietary education, followed by a tailored fructose-restricted diet in adults with fructose malabsorption

OBJECTIVE

Fructose is absorbed by GLUT transporters in the small intestine. If this process is inadequate, abdominal symptoms because of fructose intolerance may arise. The effect of a tailored fructose-restricted diet on gastrointestinal complaints was assessed in patients with fructose intolerance.

MATERIALS AND METHODS

Following an abnormal fructose breath test (50 g), 107 patients (64 also with lactose intolerance) entered three study periods: weeks 0-32 (free diet), weeks 32-36 (progressive increasing amount of fructose up to quantity inducing symptoms, 'trigger dose'), and weeks 36-48 (tailored fructose-restricted diet according to the 'trigger dose'). A subgroup of 15 patients underwent additional fructose breath tests (35, 25 g) to compare three different doses.

RESULTS

At baseline, the most frequent symptoms were bloating and abdominal pain, and were more severe with combined fructose and lactose intolerance. During the free diet, patients reported eliminating (48%) or reducing (52%) fructose-containing foods, with a significant improvement in symptoms (abdominal pain from 79.7 ± 1.3 to 19.3 ± 1.8 mm; bloating from 83.1 ± 1.3 to 19.4 ± 1.8 mm; number of evacuations/day from 3.9 ± 0.16 to 1.1 ± 0.04; Bristol score from 5.1 ± 0.14 to 3.8 ± 0.1, P < 0.00001). During the tailored fructose-restricted diet, the consistent improvement in symptoms persisted and was similar to the improvement on free diet (abdominal pain 23.6 ± 1.9 mm; bloating 19.4 ± 1.8 mm; number of evacuations/day 1.7 ± 0.07; Bristol score 3.5 ± 0.06, P<0.00001 vs. baseline). A dose-dependent effect of fructose was observed on symptoms during the fructose breath test.

CONCLUSION

In our setting, individuals with fructose intolerance show an inappropriate dietary self-management. By contrast, a tailored fructose-restricted diet improves gastrointestinal symptoms without senseless food deprivation.

Is fructose malabsorption a cause of irritable bowel syndrome?

Irritable Bowel Syndrome (IBS) is a condition that may be marked by abdominal pain, bloating, fullness, indigestion, belching, constipation and/or diarrhea. IBS symptoms can result from malabsorption of fructose. Fructose is a monosaccharide found naturally in small quantities in fruits and some vegetables, and in much larger quantities in industrially manufactured sweets with added sugars (e.g. sucrose and high fructose corn syrup). Fructose malabsorption leads to osmotic diarrhea as well as gas and bloating due to fermentation in the colon. A low-fructose diet has been found to improve IBS symptoms in some patients. This paper discusses the prevalence of fructose malabsorption and considers fructose ingestion as a possible cause of--and fructose restriction as a possible dietary treatment for--IBS.

Breath tests and irritable bowel syndrome

Breath tests are non-invasive tests and can detect H₂ and CH₄ gases which are produced by bacterial fermentation of unabsorbed intestinal carbohydrate and are excreted in the breath. These tests are used in the diagnosis of carbohydrate malabsorption, small intestinal bacterial overgrowth, and for measuring the orocecal transit time. Malabsorption of carbohydrates is a key trigger of irritable bowel syndrome (IBS)-type symptoms such as diarrhea and/or constipation, bloating, excess flatulence, headaches and lack of energy. Abdominal bloating is a common nonspecific symptom which can negatively impact quality of life. It may reflect dietary imbalance, such as excess fiber intake, or may be a manifestation of IBS. However, bloating may also represent small intestinal bacterial overgrowth. Patients with persistent symptoms of abdominal bloating and distension despite dietary interventions should be referred for H₂ breath testing to determine the presence or absence of bacterial overgrowth. If bacterial overgrowth is identified, patients are typically treated with antibiotics. Evaluation of IBS generally includes testing of other disorders that cause similar symptoms. Carbohydrate malabsorption (lactose, fructose, sorbitol) can cause abdominal fullness, bloating, nausea, abdominal pain, flatulence, and diarrhea, which are similar to the symptoms of IBS. However, it is unclear if these digestive disorders contribute to or cause the symptoms of IBS. Research studies show that a proper diagnosis and effective dietary intervention significantly reduces the severity and frequency of gastrointestinal symptoms in IBS. Thus, diagnosis of malabsorption of these carbohydrates in IBS using a breath test is very important to guide the clinician in the proper treatment of IBS patients.

Hydrogen breath tests in gastrointestinal diseases

Hydrogen breath tests are widely used to explore pathophysiology of functional gastrointestinal (GI) disorders. Small intestinal bacterial overgrowth (SIBO) and carbohydrate malabsorption are disorders detected by these tests that have been proposed to be of great importance for symptoms of GI diseases. Glucose hydrogen breath test is more acceptable for diagnosis of SIBO whereas lactose and fructose hydrogen breath tests are used for detection of lactose and fructose maldigestion respectively. Lactulose hydrogen breath test is also used widely to measure the orocecal transit time for GI motility. These methods are noninvasive and inexpensive. Many patients with functional gut disorders are unaware of the relationship between diet and GI symptoms they present. In particular, patients with chronic symptoms may regard their condition as normal and may not be aware that their symptoms can be effectively managed following a proper diagnosis. Patients with symptoms of abdominal pain, bloating, flatulence and altered bowel movements (diarrhea and constipation), or with a medical diagnosis of irritable bowel syndrome or celiac disease, may have undiagnosed carbohydrate malabsorption or SIBO. Hydrogen breath tests are specific and sensitive diagnostic tests that can be used to either confirm or eliminate the possibility of carbohydrate malabsorption or SIBO in such patients. Breath tests, though valuable tools, are underutilized in evaluating dyspepsia and functional bloating and diarrhea as well as suspected malabsorption. However, because of their simplicity, reproducibility and safety of procedure they are now being substituted to more uncomfortable and expensive techniques that were traditionally used in gastroenterology.

[Importance of diet in irritable bowel syndrome]

About two-thirds of irritable bowel syndrome (IBS) patients associate their symptoms with certain foods. We reviewed food-related factors putatively associated with manifestations of IBS. Soluble fiber may improve constipation but frequently increases bloating and abdominal pain. Carbohydrate malabsorption seems to be more frequent in IBS. A low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet significantly reduces IBS symptoms and has been suggested as a therapeutic option. Serological screening for celiac disease should be done in patients without constipation. Moreover, non-celiac disease gluten sensitivity, defined as gluten intolerance once celiac disease and wheat allergy have been ruled out, should be considered in these patients. There is no specific diet for IBS patients but small and frequent meals, avoiding greasy foods, dairy products, many carbohydrates, caffeine and alcohol, is recommended.

Extending our knowledge of fermentable, short-chain carbohydrates for managing gastrointestinal symptoms

The Monash University low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) diet is now accepted as an effective strategy for managing symptoms of irritable bowel syndrome (IBS) in Australia, with interest expanding across the world. These poorly absorbed, short-chain carbohydrates have been shown to induce IBS symptoms of diarrhea, bloating, abdominal pain, and flatus due to their poor absorption, osmotic activity, and rapid fermentation. Four clinical trials have been published to date, all with significant symptomatic response to the low FODMAP diet. Up to 86% of patients with IBS have achieved relief of overall gastrointestinal symptoms and, more specifically, bloating, flatus, abdominal pain, and altered bowel habit from the approach. This review provides an overview of the low FODMAP diet and summarizes the research to date, emerging concepts, and limitations. FODMAPs are known to be beneficial to bowel health; the importance of this and how this should be considered in the clinical management of IBS is also discussed. A clinical management flowchart is provided to assist nutrition professionals in the use of this approach.

Reliability of symptom analysis during carbohydrate hydrogen-breath tests

PURPOSE OF REVIEW

Relevance of symptom analysis during hydrogen breath test (HBT) for establishing a clinical diagnosis of sugar intolerance is reviewed.

RECENT FINDINGS

Evaluation of symptoms developed in response to the ingestion of 50 g lactose could represent a simple screening test to select patients for lactose intolerance testing. Patients who do not develop symptoms do not need to be referred for HBT. In addition, symptoms reported by patients during a negative HBT cannot be at all times attributed to a false-negative test; instead, a 'nocebo' effect is likely to be implicated. On the other hand, in a double-blind randomized study, a dose of 25 g fructose was suggested as the most appropriate for testing individuals with suspected fructose malabsorption, whereas symptom reliability to diagnose fructose intolerance was inaccurate.

SUMMARY

Whereas the development of symptoms after a positive HBT may indicate sugar intolerance, it is still not clear whether the absence of symptoms after sugar malabsorption gives any indication as to the role of that sugar in the genesis of patient's complaints. Further studies should evaluate whether the disappearance of symptoms with a sugar-restricted diet after a positive HBT is a better diagnostic criterion of sugar intolerance than the development of symptoms.

Fructose malabsorption and intolerance: effects of fructose with and without simultaneous glucose ingestion

Concern exists that increasing fructose consumption, particularly in the form of high-fructose corn syrup, is resulting in increasing rates of fructose intolerance and aggravation of clinical symptoms in individuals with irritable bowel syndrome. Most clinical trials designed to test this hypothesis have used pure fructose, a form not commonly found in the food supply, often in quantities and concentrations that exceed typical fructose intake levels. In addition, the amount of fructose provided in tests for malabsorption, which is thought to be a key cause of intolerance, often exceeds the normal physiological absorption capacity for this sugar. To help health professionals accurately identify and treat this condition, this article reviews clinical data related to understanding fructose malabsorption and intolerance (i.e., malabsorption that manifests with symptoms) relative to usual fructose and other carbohydrate intake. Because simultaneous consumption of glucose attenuates fructose malabsorption, information on the fructose and glucose content of foods, beverages, and ingredients representing a variety of food categories is provided.

Food: the forgotten factor in the irritable bowel syndrome

After years of inattention, there is a growing body of evidence to suggest that dietary constituents at least exacerbate symptoms and perhaps contribute to the pathogenesis of the irritable bowel syndrome (IBS). Although patients with IBS self-report food allergies more often than the general population, the evidence suggests that true food allergies are relatively uncommon. Less clearly defined food intolerances may be an important contributor to symptoms in IBS patients. This article reviews the literature supporting a causal link between food and the symptoms of IBS as well as the evidence supporting dietary interventions as a means of managing IBS symptoms.

Intestinal fructose transport and malabsorption in humans

Fructose is a hexose sugar that is being increasingly consumed in its monosaccharide form. Patients who exhibit fructose malabsorption can present with gastrointestinal symptoms that include chronic diarrhea and abdominal pain. However, with no clearly established gastrointestinal mechanism for fructose malabsorption, patient analysis by the proxy of a breath hydrogen test (BHT) is controversial. The major transporter for fructose in intestinal epithelial cells is thought to be the facilitative transporter GLUT5. Consistent with a facilitative transport system, we show here by analysis of past studies on healthy adults that there is a significant relationship between fructose malabsorption and fructose dose (r = 0.86, P < 0.001). Thus there is a dose-dependent and limited absorption capacity even in healthy individuals. Changes in fructose malabsorption with age have been observed in human infants, and this may parallel the developmental regulation of GLUT5 expression. Moreover, a GLUT5 knockout mouse has displayed the hallmarks associated with profound fructose malabsorption. Fructose malabsorption appears to be partially modulated by the amount of glucose ingested. Although solvent drag and passive diffusion have been proposed to explain the effect of glucose on fructose malabsorption, this could possibly be a result of the facilitative transporter GLUT2. GLUT5 and GLUT2 mRNA have been shown to be rapidly upregulated by the presence of fructose and GLUT2 mRNA is also upregulated by glucose, but in humans the distribution and role of GLUT2 in the brush border membrane are yet to be definitively decided. Understanding the relative roles of these transporters in humans will be crucial for establishing a mechanistic basis for fructose malabsorption in gastrointestinal patients.

Fructose malabsorption: true condition or a variance from normality

Fructose exists in food naturally or as a sweetening additive. It has been thought that fructose malabsorption may cause the gastrointestinal symptoms seen in patients with irritable bowel syndrome. However, fructose malabsorption is still poorly understood, and clinicians are still uncertain of its role. This review attempts to clarify the relation between fructose malabsorption and symptoms in normal individuals and patients with irritable bowel syndrome. The main problem lies in the diagnosis. First, there is no definite cut off value for the breath tests. Second, we are unsure of the normal absorptive capacity of fructose in normal individuals. Normal individuals will have a degree of fructose malabsorption with or without symptoms depending on the dose of fructose used. From earlier studies, 25 g of fructose seems to be the cut-off dose to investigate fructose malabsorption, with a positive breath test at this dose suggesting abnormally low capacity to absorb fructose. This low level may be difficult to exclude from the daily diet, resulting in symptoms of fructose malabsorption.

Abnormal breath testing in IBS: a meta-analysis

BACKGROUND

Recent evidence suggests a role for enteric bacteria in the development of symptoms in subjects with irritable bowel syndrome (IBS). The concept was initially based on the common finding of an abnormal lactulose breath test to suggest the presence of small intestinal bacterial overgrowth (SIBO). Despite successful antibiotic studies based on these findings, the premise of bacterial overgrowth was met with skepticism due to the perceived inaccuracies of breath testing in humans. In this study, we conduct a systematic review and meta-analysis of the studies using breath testing in IBS subjects with comparison to healthy controls.

METHODS

A literature search was conducted to identify studies in which breath testing was conducted in subjects with IBS. Once abstract titles were identified, studies that examined breath testing in a case-control fashion were identified for paper review. After exclusion criteria were applied, the remaining papers were examined using meta-analysis, among which the prevalence of an abnormal breath test in IBS subjects was compared. Further analysis was conducted among studies with appropriate age- and sex-matched controls.

RESULTS

Eleven studies met criteria for inclusion in the meta-analysis. Although heterogeneity was identified among studies on the basis of substrate used, lactulose was the most common substrate. In pooling the 11 studies, breath testing was more often abnormal among IBS subjects than health controls (OR=4.46, 95% CI=1.69-11.80). This was further evident in more appropriately designed age- and sex-matched studies (OR=9.64, 95% CI=4.26-21.82). The overall sensitivity and specificity for breath testing in separating IBS from healthy controls was 43.6 and 83.6%.

CONCLUSIONS

This study demonstrates that the breath test findings in IBS appear to be valid. While this meta-analysis does not suggest that the breath test findings imply SIBO, the abnormal fermentation timing and dynamics of the breath test findings support a role for abnormal intestinal bacterial distribution in IBS.

Triple sugar screen breath hydrogen test for sugar intolerance in children with functional abdominal symptoms

BACKGROUND

Sugar intolerance and functional gastrointestinal disorders are both common in school age children. Both may present with similar complaints such as abdominal pain, diarrhea and bloating. Lactose, fructose and sucrose hydrogen breath tests are widely used to detect sugar malabsorption.

AIM

To determine the proportion of children with symptoms of functional gastrointestinal disorders (FGID) that have sugar intolerance as determined by using a breath hydrogen test.

METHODS

We prospectively enrolled subjects with chronic abdominal pain, bloating and/or chronic diarrhea. All subjects underwent triple sugar screen hydrogen breath test (TSST) using the combined sugar solution. Breath hydrogen concentration ≥ 20 ppm above baseline was interpreted a positive test for sugar malabsorption.

RESULTS

A positive hydrogen breath test consistent with sugar malabsorption was found in 5 out of 31 (16%) subjects. Three of these subjects were confirmed to have lactose malabsorption based on small bowel lactase enzyme analysis or subsequent lactose hydrogen breath test. One subject with positive TSST was diagnosed with fructose malabsorption based on dietary history; he improved on a limited fructose diet, and one was diagnosed to have gastric Crohn's disease.

CONCLUSION

Approximately one in six children with symptoms of FGID had sugar intolerance as determined by the TSST.

Fructose and cardiometabolic disorders: the controversy will, and must, continue

The present review updates the current knowledge on the question of whether high fructose consumption is harmful or not and details new findings which further pushes this old debate. Due to large differences in its metabolic handling when compared to glucose, fructose was indeed suggested to be beneficial for the diet of diabetic patients. However its growing industrial use as a sweetener, especially in soft drinks, has focused attention on its potential harmfulness, possibly leading to dyslipidemia, obesity, insulin resistance/metabolic syndrome and even diabetes. Many new data have been generated over the last years, confirming the lipogenic effect of fructose as well as risks of vascular dysfunction and hypertension. Fructose exerts various direct effects in the liver, affecting both hepatocytes and Kupffer cells and resulting in non-alcoholic steatotic hepatitis, a well known precursor of the metabolic syndrome. Hepatic metabolic abnormalities underlie indirect peripheral metabolic and vascular disturbances, for which uric acid is possibly the culprit.Nevertheless major caveats exist (species, gender, source of fructose, study protocols) which are detailed in this review and presently prevent any firm conclusion. New studies taking into account these confounding factors should be undertaken in order to ascertain whether or not high fructose diet is harmful.

The role of diet in symptoms of irritable bowel syndrome in adults: a narrative review

This review summarizes what is known about the effect of diet on irritable bowel syndrome (IBS) symptoms emphasizing data from randomized, controlled clinical trials. Studies suggest that IBS symptoms in one quarter of patients may be caused or exacerbated by one or more dietary components. Recent studies indicate that a diet restricted in fermentable, poorly absorbed carbohydrates, including fructose, fructans (present in wheat and onions), sorbitol, and other sugar alcohols is beneficial, but confirmatory studies are needed. Despite a long history of enthusiastic use, fiber is marginally beneficial. Insoluble fiber may worsen symptoms. Some patients with IBS, especially those with constipation, will improve with increased intake of soluble fiber. Prebiotic fibers have not been adequately tested. Daily use of peppermint oil is effective in relieving IBS symptoms. The usefulness of probiotics in the form of foods such as live-culture yogurt and buttermilk for IBS symptoms is not established. In clinical practice, it is very difficult to establish that a patient's symptoms result from an adverse reaction to food. A double blind placebo-controlled food challenge is the most reliable method, but it is not suitable for routine clinical use. A modified exclusion diet and stepwise reintroduction of foods or trials of eliminating classes of food may be useful.

Comparison of the prevalence of fructose and lactose malabsorption across chronic intestinal disorders

BACKGROUND

Fructose malabsorption, lactose malabsorption and an early rise in breath hydrogen after lactulose (ERBHAL) may play roles in induction of symptoms in gastrointestinal conditions.

AIM

To compare prevalence and interactions of fructose malabsorption, lactose malabsorption and ERBHAL among healthy subjects and those with chronic intestinal disorders using consistent breath hydrogen testing methodologies.

METHODS

Consecutive series of Caucasian patients with Crohn's disease (n = 91), ulcerative colitis (56), functional gastrointestinal disorders (FGID) (201), coeliac disease (136) and 71 healthy volunteers underwent breath hydrogen testing using lactulose, fructose and lactose.

RESULTS

Early rise in breath hydrogen after lactulose occurred more commonly in healthy controls (39%) than in Crohn's disease (20%) and untreated coeliac disease (14%; P < 0.008), but not FGID (27%), ulcerative colitis (26%) or treated coeliac disease (29%). Fructose malabsorption was more frequent in Crohn's disease (61%) than other groups (33-44%, P < 0.05). Lactose malabsorption was most common in Crohn's disease (42%) and ulcerative colitis (40%) and uncommon (10%) in 79 patients with newly diagnosed coeliac disease. In Crohn's disease, concurrent Fructose malabsorption and lactose malabsorption was most common (29%), and the association of fructose malabsorption with ERBHAL seen overall (62%) was not observed (36%, P < 0.0001).

CONCLUSIONS

Carbohydrate malabsorption and ERBHAL are normal physiological phenomena. The abnormal patterns observed in Crohn's disease may have pathogenic importance.

Intestinal and anorectal motility and functional disorders

Motility and functional disorders of the small intestine, the colon and the anorectum can induce or contribute to symptoms such as diarrhoea, constipation and abdominal pain and may impair nutrient absorption in severe cases. Acute affections of intestinal functions e.g. during gastrointestinal infections usually need no functional diagnostics but resolve spontaneously or with adequate therapy of the underlying disease. By contrast, chronic disturbances of small intestinal, colonic and anorectal motility and/or sensitivity are subject to gastrointestinal function tests. The role of these tests for diagnosis and therapeutic handling of severe intestinal dysmotility/chronic intestinal pseudo-obstruction, severe constipation, diarrhoea, fecal incontinence and irritable bowel syndrome will be discussed in this review that mainly focuses on adults.