Dietary fructose and gastrointestinal symptoms: a review

John Yudkin's hypothesis: sugar is a major dietary culprit in the development of cardiovascular disease

To date, the risk of developing atherosclerosis has extended beyond Western countries and now affecting individuals from various ethnic backgrounds and age groups. Traditional risk factors of atherosclerosis, such as hypercholesterolemia, has been better controlled than before due to highly effective and inexpensive therapies at lowering plasma cholesterol levels. However, the role of reducing dietary cholesterol intake, as a public healthy strategy, in preventing the occurrence of cardiovascular mortalities has been recently challenged. Indeed, despite our continuous decline of dietary cholesterol intake within the last 50 years, the incidence of cardiovascular mortalities has continued to rise, thus raising the possibility that other dietary factors, such as fructose-containing sugars, are the major culprit. In the 1970s, John Yudkin first proposed that sugar was the predominant dietary factor that underlies the majority of cardiovascular mortalities, yet his hypothesis was dismissed. However, over the last 25 years substantial scientific evidence has been accumulated to support Yudkin's hypothesis. The objectives of this review are to highlight Yudkin's significant contribution to nutritional science by reviewing his hypothesis and summarizing the recent advances in our understanding of fructose metabolism. The metabolic consequences of fructose metabolism, such as fructose-induced uricemia, insulin resistance, lipoprotein hyperproduction and chronic inflammation, and how they are linked to atherosclerosis as risk factors will be discussed. Finally, the review will explore areas that warrant future research and raise important considerations that we need to evaluate when designing future studies.

Association between Dietary Intake of Live Microbes and Chronic Constipation in Adults

BACKGROUND

Chronic constipation (CC) is a common gut health problem, and the role of live dietary microbes in CC is unclear.

OBJECTIVE

This study aimed to investigate the relationship between dietary live microbes consumption and CC.

METHODS

Using the National Health and Nutrition Examination Survey data (2005-2010), 11,170 adults who completed the 24-h face-to-face dietary recall and bowel health questionnaire were identified. CC was defined by the Bristol Stool Form Scale. Dietary live microbes intake was classified as low, medium, and high. Additionally, combined medium and high categories (MedHi) were analyzed. Multivariate regression models were constructed to assess the association between dietary intake of live microbes and CC.

RESULTS

In the weighted sample, the age-adjusted CC prevalence was 7.06% (95% confidence interval [CI]: 6.45, 7.67). In multivariate regression models, after controlling for potential confounders race/ethnicity, sex, body mass index, education, poverty, depression, caffeine intake, and alcohol intake, a significant inverse association between dietary live microbes consumption and CC was observed (odds ratio [OR]: 0.77, 95% CI: 0.61, 0.97, P-trend = 0.061).

CONCLUSIONS

Our findings suggest that a high dietary live microbes consumption may be associated with lower odds of CC. However, further prospective studies are essential to confirm its effectiveness in reducing CC occurrence.

Association of fructose consumption with prevalence of functional gastrointestinal disorders manifestations: results from Hellenic National Nutrition and Health Survey (HNNHS)

The study aimed to assess the total prevalence of functional gastrointestinal disorders (FGID), and separately, irritable bowel syndrome (IBS) among adults and to determine their potential association with fructose consumption. Data from the Hellenic National Nutrition and Health Survey were included (3798 adults; 58·9 % females). Information regarding FGID symptomatology was assessed using self-reported physician diagnosis questionnaires the reliability of which were screened using the ROME III, in a sample of the population. Fructose intake was estimated from 24 h recalls, and the MedDiet score was used to assess adherence to the Mediterranean diet. The prevalence of FGID symptomatology was 20·2 %, while 8·2 % had IBS (representing 40·2 % of total FGID). The likelihood of FGID was 28 % higher (95 %CI: 1·03-1·6) and of IBS 49 % (95 %CI: 1·08-2·05) in individuals with higher fructose intake than with lower intake (3rd tertile compared with 1st). When area of residence was accounted for, individuals residing in the Greek islands had a significantly lower probability of FGID and IBS compared with those residing in Mainland and the main Metropolitan areas, with Islanders also achieving a higher MedDiet score and lower added sugar intake, comparatively to inhabitants of the main metropolitan areas. FGID and IBS symptomatology was most prominent among individuals with higher fructose consumption, and this was most conspicuous in areas with a lower Mediterranean diet adherence, suggesting that the dietary source of fructose rather than total fructose should be examined in relation to FGID.

Theories behind the effect of starch‑ and sucrose‑reduced diets on gastrointestinal symptoms in irritable bowel syndrome (Review)

Increased amounts of starch and sugar have been added to the diet in the Western world during the last decades. Undigested carbohydrates lead to bacterial fermentation and gas production with diffusion of water, causing abdominal bloating, pain and diarrhea. Therefore, dietary advice is the first line of treatment of irritable bowel syndrome (IBS), a disease characterized by abdominal pain and altered bowel habits without any organic findings. Recently, a diet with a reduction of starch and sucrose led to a marked effect on gastrointestinal (GI) symptoms. The mechanism is unknown, but three possible mechanisms are presented in the present review. First, functional variants of the enzyme sucrase‑isomaltase (SI) have been described in IBS. A subgroup of patients with IBS may thus suffer from partial SI deficiency with reduced digestion of starch and sucrose. Second, fructose absorption is less efficient than glucose absorption, which may lead to a physiological fructose malabsorption when ingesting high amounts of sucrose. A third mechanism is that high‑sugar diets causing hyperglycemia, hyperinsulinemia and weight gain have led to painful neuropathy in animal models; whereas, improved metabolic control in humans has led to improvement of neuropathy. Starch‑ and sucrose‑reduced diets lead to decreased levels of C‑peptide, insulin, gastric inhibitory peptide, leptin and weight reduction. These metabolic changes may reduce the excitability of the hypersensitive nervous system often found in IBS and, thereby, lead to the reduced symptoms found after the diet. In conclusion, further studies are needed to investigate the pathophysiology behind development of symptoms after starch and sucrose intake, and the mechanisms behind symptom relief after reduced intake.

Small and Large Intestine (I): Malabsorption of Nutrients

Numerous disorders can alter the physiological mechanisms that guarantee proper digestion and absorption of nutrients (macro- and micronutrients), leading to a wide variety of symptoms and nutritional consequences. Malabsorption can be caused by many diseases of the small intestine, as well as by diseases of the pancreas, liver, biliary tract, and stomach. This article provides an overview of pathophysiologic mechanisms that lead to symptoms or complications of maldigestion (defined as the defective intraluminal hydrolysis of nutrients) or malabsorption (defined as defective mucosal absorption), as well as its clinical consequences, including both gastrointestinal symptoms and extraintestinal manifestations and/or laboratory abnormalities. The normal uptake of nutrients, vitamins, and minerals by the gastrointestinal tract (GI) requires several steps, each of which can be compromised in disease. This article will first describe the mechanisms that lead to poor assimilation of nutrients, and secondly discuss the symptoms and nutritional consequences of each specific disorder. The clinician must be aware that many malabsorptive disorders are manifested by subtle disorders, even without gastrointestinal symptoms (for example, anemia, osteoporosis, or infertility in celiac disease), so the index of suspicion must be high to recognize the underlying diseases in time.

Methane breath tests and blood sugar tests in children with suspected carbohydrate malabsorption

Carbohydrate malabsorption and subsequent gastrointestinal symptoms are a common clinical problem in pediatrics. Hydrogen (H₂) and methane (CH₄) breath tests are a cheap and non-invasive procedure for diagnosing fructose and lactose malabsorption (FM/LM) but test accuracy and reliability as well as the impact of non-hydrogen producers (NHP) is unclear. CH₄ breath tests (MBT), blood sugar tests (BST) and clinical symptoms were compared with H₂ breath tests (HBT) for FM/LM. 187/82 tests were performed in children (2 to 18 years) with unclear chronic/recurrent abdominal pain and suspected FM/LM. In FM and LM, we found a significant correlation between HBT and MBT/BST. In LM, MBT differentiated most of the patients correctly and BST might be used as an exclusion test. However, additional MBT and BST had no diagnostic advantage in FM. NHP still remain a group of patients, which cannot be identified using the recommended CH₄ cut-off values in FM or LM. Reported symptoms during breath tests are not a reliable method to diagnose FM/LM. Overall a combined test approach might help in diagnosing children with suspected carbohydrate malabsorption.

Glucose transporters in the small intestine in health and disease

Absorption of monosaccharides is mainly mediated by Na+-D-glucose cotransporter SGLT1 and the facititative transporters GLUT2 and GLUT5. SGLT1 and GLUT2 are relevant for absorption of D-glucose and D-galactose while GLUT5 is relevant for D-fructose absorption. SGLT1 and GLUT5 are constantly localized in the brush border membrane (BBM) of enterocytes, whereas GLUT2 is localized in the basolateral membrane (BLM) or the BBM plus BLM at low and high luminal D-glucose concentrations, respectively. At high luminal D-glucose, the abundance SGLT1 in the BBM is increased. Hence, D-glucose absorption at low luminal glucose is mediated via SGLT1 in the BBM and GLUT2 in the BLM whereas high-capacity D-glucose absorption at high luminal glucose is mediated by SGLT1 plus GLUT2 in the BBM and GLUT2 in the BLM. The review describes functions and regulations of SGLT1, GLUT2, and GLUT5 in the small intestine including diurnal variations and carbohydrate-dependent regulations. Also, the roles of SGLT1 and GLUT2 for secretion of enterohormones are discussed. Furthermore, diseases are described that are caused by malfunctions of small intestinal monosaccharide transporters, such as glucose-galactose malabsorption, Fanconi syndrome, and fructose intolerance. Moreover, it is reported how diabetes, small intestinal inflammation, parental nutrition, bariatric surgery, and metformin treatment affect expression of monosaccharide transporters in the small intestine. Finally, food components that decrease D-glucose absorption and drugs in development that inhibit or downregulate SGLT1 in the small intestine are compiled. Models for regulations and combined functions of glucose transporters, and for interplay between D-fructose transport and metabolism, are discussed.

A Single Load of Fructose Attenuates the Risk of Exercise-Induced Hypoglycemia in Adults With Type 1 Diabetes on Ultra-Long-Acting Basal Insulin: A Randomized, Open-Label, Crossover Proof-of-Principle Study

OBJECTIVE

While the adjustment of insulin is an established strategy to reduce the risk of exercise-associated hypoglycemia for individuals with type 1 diabetes, it is not easily feasible for those treated with ultra-long-acting basal insulin. The current study determined whether pre-exercise intake of fructose attenuates the risk of exercise-induced hypoglycemia in individuals with type 1 diabetes using insulin degludec.

RESEARCH DESIGN AND METHODS

Fourteen male adults with type 1 diabetes completed two 60-min aerobic cycling sessions with or without prior intake (30 min) of 20 g of fructose, in a randomized two-period crossover design. Exercise was performed in the morning in a fasted state without prior insulin reduction and after 48 h of standardized diet. The primary outcome was time to hypoglycemia (plasma glucose ≤3.9 mmol/L) during exercise.

RESULTS

Intake of fructose resulted in one hypoglycemic event at 60 min compared with six hypoglycemic events at 27.5 ± 9.4 min of exercise in the control condition, translating into a risk reduction of 87.8% (hazard ratio 0.12 [95% CI 0.02, 0.66]; P = 0.015). Mean plasma glucose during exercise was 7.3 ± 1.4 mmol/L with fructose and 5.5 ± 1.1 mmol/L in the control group (P < 0.001). Lactate levels were higher at rest in the 30 min following fructose intake (P < 0.001) but were not significantly different from the control group during exercise (P = 0.32). Substrate oxidation during exercise did not significantly differ between the conditions (P = 0.73 for carbohydrate and P = 0.48 for fat oxidation). Fructose was well tolerated.

CONCLUSIONS

Pre-exercise intake of fructose is an easily feasible, effective, and well-tolerated strategy to alleviate the risk of exercise-induced hypoglycemia while avoiding hyperglycemia in individuals with type 1 diabetes on ultra-long-acting insulin.

High intestinal hydrogen production in runners after intake of fructose solution

Fructose intake is associated with increased consumption of processed foods, specifically in the context of nutritional supplements. To assess gastrointestinal symptoms and hydrogen production after the ingestion of a fructose solution in runners, healthy and sick persons. Hydrogen test (H2 test) was performed after the intake a solution with 50 g fructose along with the application of a questionnaire to evaluate the gastrointestinal symptoms during the H2 test in three groups: Athletes group (AG); control group (CG) with healthy subjects; and non-alcoholic fatty liver disease group (NAFLDG). Statistical analysis was performed with analysis of variance at a p < 0.05 significance level. The AG was the largest H₂ producer followed by the CG with significant difference between the AG and NAFLDG (p ≤ 0.05). Most participants remained asymptomatic, but the strongest correlation was the symptom of bloating GC (R = 0.625), eructation in NAFLD (R = 0.481) and diarrhea in CG (R = 0.345) and AG (R = 0.338) The result of the present study suggests the production of hydrogen by the colon following the administration of fructose is higher in athletes compared with healthy individuals and persons with NAFLD, showing that fructose intake may be an interesting point of dietary management, especially in elite professionals.

Mechanisms, Evaluation, and Management of Chronic Constipation

With a worldwide prevalence of 15%, chronic constipation is one of the most frequent gastrointestinal diagnoses made in ambulatory medicine clinics, and is a common source cause for referrals to gastroenterologists and colorectal surgeons in the United States. Symptoms vary among patients; straining, incomplete evacuation, and a sense of anorectal blockage are just as important as decreased stool frequency. Chronic constipation is either a primary disorder (such as normal transit, slow transit, or defecatory disorders) or a secondary one (due to medications or, in rare cases, anatomic alterations). Colonic sensorimotor disturbances and pelvic floor dysfunction (such as defecatory disorders) are the most widely recognized pathogenic mechanisms. Guided by efficacy and cost, management of constipation should begin with dietary fiber supplementation and stimulant and/or osmotic laxatives, as appropriate, followed, if necessary, by intestinal secretagogues and/or prokinetic agents. Peripherally acting μ-opiate antagonists are another option for opioid-induced constipation. Anorectal tests to evaluate for defecatory disorders should be performed in patients who do not respond to over-the-counter agents. Colonic transit, followed if necessary with assessment of colonic motility with manometry and/or a barostat, can identify colonic dysmotility. Defecatory disorders often respond to biofeedback therapy. For specific patients, slow-transit constipation may necessitate a colectomy. No studies have compared inexpensive laxatives with newer drugs with different mechanisms. We review the mechanisms, evaluation, and management of chronic constipation. We discuss the importance of meticulous analyses of patient history and physical examination, advantages and disadvantages of diagnostic testing, guidance for individualized treatment, and management of medically refractory patients.

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.

The extra-splanchnic fructose escape after ingestion of a fructose-glucose drink: An exploratory study in healthy humans using a dual fructose isotope method

BACKGROUND & AIMS

The presence of specific fructose transporters and fructose metabolizing enzymes has now been demonstrated in the skeletal muscle, brain, heart, adipose tissue and many other tissues. This suggests that fructose may be directly metabolized and play physiological or pathophysiological roles in extra-splanchnic tissues. Yet, the proportion of ingested fructose reaching the systemic circulation is generally not measured. This study aimed to assess the amount of oral fructose escaping first-pass splanchnic extraction after ingestion of a fructose-glucose drink using a dual oral-intravenous fructose isotope method.

METHODS

Nine healthy volunteers were studied over 2 h before and 4 h after ingestion of a drink containing 30.4 ± 1.0 g of glucose (mean ± SEM) and 30.4 ± 1.0 g of fructose labelled with 1% [U-¹³C₆]-fructose. A 75%-unlabeled fructose and 25%-[6,6-²H₂]-fructose solution was continuously infused (100 μg kg^-1 min^-1) over the 6 h period. Total systemic, oral and endogenous fructose fluxes were calculated from plasma fructose concentrations and isotopic enrichments. The fraction of fructose escaping first-pass splanchnic extraction was calculated assuming a complete intestinal absorption of the fructose drink.

RESULTS

Fasting plasma fructose concentration before tracer infusion was 17.9 ± 0.6 μmol.L^-1. Fasting endogenous fructose production detected by tracer dilution analysis was 55.3 ± 3.8 μg kg^-1min^-1. Over the 4 h post drink ingestion, 4.4 ± 0.2 g of ingested fructose (i.e. 14.5 ± 0.8%) escaped first-pass splanchnic extraction and reached the systemic circulation. Endogenous fructose production significantly increased to a maximum of 165.4 ± 10.7 μg kg^-1·min^-1 60 min after drink ingestion (p < 0.001).

CONCLUSIONS

These data indicate that a non-negligible fraction of fructose is able to escape splanchnic extraction and circulate in the periphery. The metabolic effects of direct fructose metabolism in extra-splanchnic tissues, and their relationship with metabolic diseases, remain to be evaluated. Our results also open new research perspectives regarding the physiological role of endogenous fructose production.

Fructose metabolism, cardiometabolic risk, and the epidemic of coronary artery disease

Despite strong indications that increased consumption of added sugars correlates with greater risks of developing cardiometabolic syndrome (CMS) and cardiovascular disease (CVD), independent of the caloric intake, the worldwide sugar consumption remains high. In considering the negative health impact of overconsumption of dietary sugars, increased attention is recently being given to the role of the fructose component of high-sugar foods in driving CMS. The primary organs capable of metabolizing fructose include liver, small intestine, and kidneys. In these organs, fructose metabolism is initiated by ketohexokinase (KHK) isoform C of the central fructose-metabolizing enzyme KHK. Emerging data suggest that this tissue restriction of fructose metabolism can be rescinded in oxygen-deprived environments. In this review, we highlight recent progress in understanding how fructose metabolism contributes to the development of major systemic pathologies that cooperatively promote CMS and CVD, reference recent insights into microenvironmental control of fructose metabolism under stress conditions and discuss how this understanding is shaping preventive actions and therapeutic approaches.

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.

Fructose metabolism and metabolic disease

Increased sugar consumption is increasingly considered to be a contributor to the worldwide epidemics of obesity and diabetes and their associated cardiometabolic risks. As a result of its unique metabolic properties, the fructose component of sugar may be particularly harmful. Diets high in fructose can rapidly produce all of the key features of the metabolic syndrome. Here we review the biology of fructose metabolism as well as potential mechanisms by which excessive fructose consumption may contribute to cardiometabolic disease.

Food avoidance in athletes: FODMAP foods on the list

We surveyed 910 athletes to assess behaviours towards self-selected food/ingredient avoidance to minimize gastrointestinal distress. Fifty-five percent eliminated at least 1 high fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) food/category, with up to 82.6% reporting symptom improvement. In athletes indicating that high FODMAP foods trigger gastrointestinal symptoms, lactose (86.5%) was most frequently eliminated, followed by galactooligosaccharides (23.9%), fructose (23.0%), fructans (6.2%), and polyols (5.4%). Athletes avoid predominantly lactose and to a lesser extent other high FODMAP foods to reduce gastrointestinal distress.

No difference in ad libitum energy intake in healthy men and women consuming beverages sweetened with fructose, glucose, or high-fructose corn syrup: a randomized trial

BACKGROUND

Increased energy intake is consistently observed in individuals consuming sugar-sweetened beverages (SSBs), likely mainly because of an inadequate satiety response to liquid calories. However, SSBs have a high content of fructose, the consumption of which acutely fails to trigger responses in key signals involved in energy homeostasis. It is unclear whether the fructose content of SSBs contributes to the increased energy intake in individuals drinking SSBs.

OBJECTIVE

We investigated whether the relative amounts of fructose and glucose in SSBs modifies ad libitum energy intake over 8 d in healthy adults without fructose malabsorption.

DESIGN

We conducted 2 randomized, controlled, double-blind crossover studies to compare the effects of consuming 4 servings/d of a fructose-, glucose-, or aspartame-sweetened beverage (study A; n = 9) or a fructose-, glucose-, or high-fructose corn syrup (HFCS)-sweetened beverage (study B; n = 24) for 8 d on overall energy intake. SSBs were provided at 25% of estimated energy requirement, or an equivalent volume of the aspartame-sweetened beverage, and consumption was mandatory. All solid foods were provided at 125% of estimated energy requirements and were consumed ad libitum.

RESULTS

In study A, ad libitum energy intake was 120% ± 10%, 117% ± 12%, and 102% ± 15% of estimated energy requirements when subjects consumed the fructose-, glucose-, and aspartame-sweetened beverages. Energy intake was significantly higher in the fructose and glucose phases than in the aspartame phase (P < 0.003 for each), with no difference between the fructose and glucose phases (P = 0.462). In study B, total energy intake during the fructose, HFCS, and glucose phases was 116% ± 14%, 116% ± 16%, and 116% ± 16% of the subject's estimated total energy requirements (P = 0.880).

CONCLUSIONS

In healthy adults, total 8-d ad libitum energy intake was increased in individuals consuming SSBs compared with aspartame-sweetened beverages. The energy overconsumption observed in individuals consuming SSBs occurred independently of the relative amounts of fructose and glucose in the beverages. These trials were registered at clinicaltrials.gov as NCT00475475 and NCT01424306.

Natural Selection at the Brush-Border: Adaptations to Carbohydrate Diets in Humans and Other Mammals

Dietary shifts can drive molecular evolution in mammals and a major transition in human history, the agricultural revolution, favored carbohydrate consumption. We investigated the evolutionary history of nine genes encoding brush-border proteins involved in carbohydrate digestion/absorption. Results indicated widespread adaptive evolution in mammals, with several branches experiencing episodic selection, particularly strong in bats. Many positively selected sites map to functional protein regions (e.g., within glucosidase catalytic crevices), with parallel evolution at SI (sucrase-isomaltase) and MGAM (maltase-glucoamylase). In human populations, five genes were targeted by positive selection acting on noncoding variants within regulatory elements. Analysis of ancient DNA samples indicated that most derived alleles were already present in the Paleolithic. Positively selected variants at SLC2A5 (fructose transporter) were an exception and possibly spread following the domestication of specific fruit crops. We conclude that agriculture determined no major selective event at carbohydrate metabolism genes in humans, with implications for susceptibility to metabolic disorders.

Irritable bowel syndrome: contemporary nutrition management strategies

Irritable bowel syndrome is a complex disorder whose pathophysiology involves alterations in the enteric microbiota, visceral hypersensitivity, gut immune/barrier function, hypothalamic-pituitary-adrenal axis regulation, neurotransmitters, stress response, psychological factors, and more. The importance of diet in the management of irritable bowel syndrome has taken center stage in recent times as the literature validates the relationship of certain foods with the provocation of symptoms. Likewise, a number of elimination dietary programs have been successful in alleviating irritable bowel syndrome symptoms. Knowledge of the dietary management strategies for irritable bowel syndrome will help guide nutritionists and healthcare practitioners to deliver optimal outcomes. This tutorial reviews the nutrition management strategies for irritable bowel syndrome.

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.

Fructose-induced symptoms beyond malabsorption in FGID

The dietary carbohydrate fructose can be incompletely absorbed in the small intestine and is sometimes associated with gastrointestinal symptoms that include motility disturbances and abdominal pain. Fructose malabsorption has been well documented in variable but similar proportions of healthy and populations with functional gastrointestinal disorders. Recent work into the expression of the main intestinal fructose transporter proteins highlight that our understanding of the mechanistic basis for fructose malabsorption and how it differentiates in gastrointestinal patients is incomplete. Until we have further mechanistic insight, restricting dietary fructose intake and other poorly absorbed short-chain carbohydrates and polyols remains an efficacious approach for managing functional gastrointestinal symptoms.

Fructose intolerance/malabsorption and recurrent abdominal pain in children

OBJECTIVES

The purpose of the present study was to ascertain whether pediatric patients with chronic abdominal pain had concurrent fructose intolerance as determined by a standardized dose breath hydrogen test (BHT), and whether symptoms would improve with a low-fructose diet.

METHODS

The fructose BHT test was administered to patients evaluated in clinic with unexplained chronic abdominal pain alone or associated with constipation, gas or bloating, and/or diarrhea. The patients were given a standard dose of 1 g/kg fructose to maximum of 25 g. Hydrogen and methane were measured at 8 time points. The test was presumed positive if breath hydrogen exceeded 20 ppm above baseline. If positive, patients were given a dietitian-prescribed low-fructose diet.

RESULTS

A total of 222 patients were part of the study. Ages ranged from 2 to 19 years with a mean of 10.5. BHT for fructose was performed in all of the patients and it was positive for fructose intolerance in 121 of 222 patients (54.5%). A total of 101 of 222 (45.5%) patients had negative BHT for fructose intolerance. All BHT-positive patients had a nutrition consult with a registered dietitian and were placed on a low-fructose diet. Using a standard pain scale for children, 93 of 121 patients (76.9%) reported resolution of symptoms on a low-fructose diet (P < 0.0001). Furthermore, 55 of 101 patients (54.4%) with negative BHT for fructose reported resolution of symptoms without a low-fructose diet (P = 0.37).

CONCLUSIONS

Fructose intolerance/malabsorption is common in children with recurrent/functional abdominal pain and a low-fructose diet is an effective treatment.

Significance of hydrogen breath tests in children with suspected carbohydrate malabsorption

BACKGROUND

Hydrogen breath tests are noninvasive procedures frequently applied in the diagnostic workup of functional gastrointestinal disorders. Here, we review hydrogen breath test results and the occurrence of lactose, fructose and sorbitol malabsorption in pediatric patients; and determine the significance of the findings and the outcome of patients with carbohydrate malabsorption.

METHODS

We included 206 children (88 male, 118 female, median age 10.7 years, range 3-18 years) with a total of 449 hydrogen breath tests (lactose, n = 161; fructose, n = 142; sorbitol, n = 146) into a retrospective analysis. Apart from test results, we documented symptoms, the therapeutic consequences of the test, the outcome and the overall satisfaction of the patients and families.

RESULTS

In total, 204 (46%) of all breath tests were positive. Long-term follow-up data could be collected from 118 patients. Of 79 patients (67%) who were put on a diet reduced in lactose, fructose and/or sorbitol, the majority (92%, n = 73) reported the diet to be strict and only 13% (n = 10) had no response to diet. Most families (96%, n = 113) were satisfied by the test and the therapy. There were only 21 tests (5%) with a borderline result because the criteria for a positive result were only partially met.

CONCLUSIONS

Hydrogen breath tests can be helpful in the evaluation of children with gastrointestinal symptoms including functional intestinal disorders. If applied for a variety of carbohydrates but only where indicated, around two-third of all children have positive results. The therapeutic consequences are successfully relieving symptoms in the vast majority of patients.

A high-fat diet differentially affects the gut metabolism and blood lipids of rats depending on the type of dietary fat and carbohydrate

The aim of this model study was to investigate how selected gut functions and serum lipid profile in rats on high-fat diets differed according to the type of fat (saturated vs. unsaturated) and carbohydrate (simple vs. complex). The experiment was conducted using 32 male Wistar rats distributed into 4 groups of 8 animals each. For 4 weeks, the animals were fed group-specific diets that were either rich in lard or soybean oil (16% of the diet) as the source of saturated or unsaturated fatty acids, respectively; further, each lard- and soybean oil-rich diet contained either fructose or corn starch (45.3% of the diet) as the source of simple or complex carbohydrates, respectively. Both dietary factors contributed to changes in the caecal short-chain fatty acid concentrations, especially to the butyrate concentration, which was higher in rats fed lard- and corn starch-rich diets compared to soybean oil- and fructose-rich diets, respectively. The lowest butyrate concentration was observed in rats fed the soybean oil- and fructose-rich diet. On the other hand, the lard- and fructose-rich diet vs. the other dietary combinations significantly increased serum total cholesterol concentration, to more than two times serum triglyceride concentration and to more than five times the atherogenic index. In conclusion, a high-fat diet rich in fructose can unfavorably affect gut metabolism when unsaturated fats are predominant in the diet or the blood lipids when a diet is rich in saturated fats.

Effect of fructose-reduced diet in patients with irritable bowel syndrome, and its correlation to a standard fructose breath test

OBJECTIVES

To perform a validation of dairy registrations for use as diagnostic tool in IBS and fructose malabsorption (FM). To investigate the precision of the fructose breath test (FBT) as compared with symptom score reduction on fructose-reduced diet (FRD) in a cohort of patients with Rome II defined irritable bowel syndrome (IBS).

DESIGN

IBS patients diagnosed according to the Rome II criteria and with no organic gastrointestinal disease were enrolled. The patients were randomized in an open study design with a 2 week run-in on IBS diet, followed by 4 weeks w/wo additional FRD. FBT was performed in all patients. Dairy registrations of stool frequency and consistency as well as abdominal pain/discomfort and bloating on a visual analog scale (VAS) were performed during the whole study.

RESULTS

A total of 182 subjects performed the study according to protocol (88 FRD, 94 controls). The VAS symptom registration performed well in validation procedures, whereas stool data showed less impressive characteristics. FRD improved symptom scores (abdominal pain/discomfort and bloating) significantly whereas no changes were observed in the control group. The effect of FRD on the stool frequency was modest but no effect was observed on the stool consistency. The FBT did not discriminate between patients with and without effect of FRD, and even in the group with a negative FBT significant improvement of symptom scores was observed.

CONCLUSION

VAS measures yield reliable symptom evaluation in dairy registrations of IBS. FRD improves symptom scores in IBS patients independent of results from the FBT.

Caffeoylquinic acid-rich extract from chicory seeds improves glycemia, atherogenic index, and antioxidant status in rats

OBJECTIVE

Comparison of the effects of a high-fructose diet supplemented with rutin, a phenolic compound with well-recognized bioavailability and bioactivity, and a chicory (Cichorium intybus L.) seed extract rich in caffeoylquinic acids (CQA) on gut physiology and the development of disorders related to metabolic syndrome.

METHODS

A 28-d experiment was conducted on 32 young male Wistar rats. In comparison with control rats fed a standard corn starch diet (group C), the experimental group (group E) was fed a diet with an increased content of cholesterol and fructose (to 1% and 66% of the diet, respectively), as well as with oxidized soybean oil. Rats from the other two experimental groups were administered the same diet as group E during the first 2 wk of feeding, whereas at the beginning of the last 2 wk, the diet was enriched with rutin (group ER) or the CQA-rich ethanol extract from chicory seeds (9.6% of CQA, group EC), so the amount of added phenolics was equal in both dietary groups (0.15%).

RESULTS

The diet administered in group E caused hyperglycemia and increased blood serum atherogenicity in rats, but did not induce other manifestations of the metabolic syndrome, i.e., dyslipidemia and oxidative stress. Additionally, it affected gut physiology through increasing mucosal sucrase activity and disturbing fermentative processes in the cecum, such as the production of short-chain fatty acids and the activity of microbial enzymes. Similarly to rutin, the dietary addition of the chicory seed extract improved glycemia, which was comparable to that determined in group C. In addition, the extract was found to decrease the atherogenic index to the level observed in group C and to increase blood antioxidant status. Both dietary supplements reduced the content of thiobarbituric acid-reactive substances in kidney and heart tissue when compared with group E.

CONCLUSION

The potential efficacy of the CQA-rich extract from chicory seeds in improving diet-induced metabolic disturbances proved to be better than that of rutin; thus, the extract might be considered as a dietary supplement for carrying out clinical trials.

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.

The prevalence of celiac disease among patients with nonconstipated irritable bowel syndrome is similar to controls

BACKGROUND & AIMS

Guidelines recommend that patients with symptoms of nonconstipated irritable bowel syndrome (NC-IBS) undergo testing for celiac disease (CD). We evaluated the prevalence of CD antibodies, and biopsy confirmed CD among patients with NC-IBS in a large US population.

METHODS

In a study conducted at 4 sites, from 2003 to 2008, we compared data from 492 patients with symptoms of NC-IBS to 458 asymptomatic individuals who underwent colonoscopy examinations for cancer screening or polyp surveillance (controls). All participants provided blood samples for specific and nonspecific CD-associated antibodies. Additionally, patients with IBS were analyzed for complete blood cell counts, metabolic factors, erythrocyte sedimentation rates, and levels of C-reactive protein and thyroid-stimulating hormone. Any subjects found to have CD-associated antibodies were offered esophagogastroduodenoscopy and duodenal biopsy analysis.

RESULTS

Of patients with NC-IBS, 7.3% had abnormal results for CD-associated antibodies, compared with 4.8% of controls (adjusted odds ratio, 1.49; 95% confidence interval: 0.76-2.90; P=.25). Within the NC-IBS group, 6.51% had antibodies against gliadin, 1.22% against tissue transglutaminase, and 0.61% against endomysium (P>.05 vs controls for all antibodies tested). CD was confirmed in 0.41% of patients in the NC-IBS group and 0.44% of controls (P>.99).

CONCLUSIONS

Although CD-associated antibodies are relatively common, the prevalence of CD among patients with NC-IBS is similar to that among controls in a large US population. These findings challenge recommendations to routinely screen patients with NC-IBS for CD. More than 7% of patients with NC-IBS had CD-associated antibodies, suggesting that gluten sensitivity might mediate IBS symptoms; further studies are needed.

Fructose addition to a glucose supplement modifies perceived exertion during strength and endurance exercise

The addition of fructose (F) to a glucose (G) supplement may modify the metabolic response during exercise; however, its effect on perceived exertion (PE) and its influence on postprandial metabolism have not been jointly studied in different types of exercise. This study sought to assess the acute effects of F addition to a G supplement on PE and on the postprandial metabolic response during a single bout of either strength exercise (SE) or endurance exercise (EE). Twenty physically trained men ingested an oral dose of G or GF 15 minutes before starting a 30-minute session of SE (10 sets of 10 repetitions of half squat) or EE (cycling). The combination resulted in 4 randomized interventions in a crossover design in which all subjects performed all experimental conditions: G + SE, GF + SE, G + EE, and GF + SE. Perceived exertion, heart rate (HR), G, insulin, lactate, and urinary catecholamine levels were measured before exercise, during the exercise, and during acute recovery. Perceived exertion during exercise was lower for GF than for G during SE and EE (mean ± SD; 8.95 ± 0.62 vs. 9.26 ± 0.65, p < 0.05 and 7.47 ± 0.84 vs. 7.74 ± 0.93, p < 0.05, respectively). The glycemic peak in GF + SE was lower than in G + SE (p < 0.05), and there was a second peak during recovery (p < 0.05), whereas in EE, no difference in blood G levels was noted between G and GF supplements. Moreover, HR, urinary adrenalin, and noradrenalin were lower in GF than in G (p < 0.05), though only for EE. The results showed that PE is positively affected by GF supplementation for both SE and EE and thus may be a useful dietary strategy for helping to achieve higher training loads.

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.

Arterial hypertension due to fructose ingestion: model based on intermittent osmotic fluid trapping in the small bowel

Based on recently reported data that fructose ingestion is linked to arterial hypertension, a model of regulatory loops involving the colon role in maintenance of fluid and sodium homeostasis is proposed.In normal digestion of hyperosmolar fluids, also in cases of postprandial hypotension and in patients having the "dumping" syndrome after gastric surgery, any hyperosmolar intestinal content is diluted by water taken from circulation and being trapped in the bowel until reabsorption. High fructose corn sirup (HFCS) soft drinks are among common hyperosmolar drinks. Fructose is slowly absorbed through passive carrier-mediated facilitated diffusion, along the entire small bowel, thus preventing absorption of the trapped water for several hours.Here presented interpretation is that ingestion of hyperosmolar HFCS drinks due to a transient fluid shift into the small bowel increases renin secretion and sympathetic activity, leading to rise in ADH and aldosterone secretions. Their actions spare water and sodium in the large bowel and kidneys. Alteration of colon absorption due to hormone exposure depends on cell renewal and takes days to develop, so the momentary capacity of sodium absorption in the colon depends on the average aldosterone and ADH exposure during few previous days. This inertia in modulation of the colon function can make an individual that often takes HFCS drinks prone to sodium retention, until a new balance is reached with an expanded ECF pool and arterial hypertension. In individuals with impaired fructose absorption, even a higher risk of arterial hypertension can be expected.

Respostas metabólicas à suplementação com frutose em exercício de força de membros inferiores

A frutose, por seu metabolismo independente da insulina, realiza significativas alterações no metabolismo hepático, promovendo um entorno metabólico favorável ao metabolismo tanto da glicose como dos lipídios, durante o exercício. Essa condição tem sido bastante estudada em exercício de endurance; no entanto, nenhum estudo sobre a suplementação com frutose no exercício de força (EF) foi encontrado. O objetivo do presente estudo foi avaliar os efeitos agudos da adição de frutose a um suplemento de glicose sobre o metabolismo de lipídios em EF. Vinte homens treinados ingeriram suplemento de glicose (G) ou glicose mais frutose (G+F), 15 minutos antes de realizar exercício de força (10 séries de 10 repetições). Os sujeitos foram testados em ordem randômica em um desenho cruzado e com uma semana de intervalo em duas condições experimentais: EF+(G) e EF+(G+F). A análise dos resultados mostrou que os valores de triglicérides durante o exercício foram maiores (p < 0,05) quando os sujeitos foram suplementados com G+F do que quando suplementados apenas com G. Ao final do exercício, os valores de ácidos graxos livres foram maiores quando os sujeitos foram suplementados G+F (p < 0,05). A glicemia foi menor durante o exercício e maior na recuperação (p < 0,05) para essa condição. O comportamento da insulina não diferiu entre os experimentos durante o exercício de força (p > 0,05), mas foi maior em G+F que em G (p < 0,05) durante a recuperação. A percepção subjetiva de esforço (PSE) foi menor (p < 0,05) para a suplementação com G+F do que com G. Em conclusão, a suplementação com G+F afeta positivamente o metabolismo de lipídios durante o exercício de força e favorece seu metabolismo imediatamente após o esforço, proporcionando condição metabólica que reflete em uma condição que afeta favoravelmente a PSE.

Heterogeneous effects of fructose on blood lipids in individuals with type 2 diabetes: systematic review and meta-analysis of experimental trials in humans

OBJECTIVE

Because of blood lipid concerns, diabetes associations discourage fructose at high intakes. To quantify the effect of fructose on blood lipids in diabetes, we conducted a systematic review and meta-analysis of experimental clinical trials investigating the effect of isocaloric fructose exchange for carbohydrate on triglycerides, total cholesterol, LDL cholesterol, and HDL cholesterol in type 1 and 2 diabetes.

RESEARCH DESIGN AND METHODS

We searched MEDLINE, EMBASE, CINAHL, and the Cochrane Library for relevant trials of > or =7 days. Data were pooled by the generic inverse variance method and expressed as standardized mean differences with 95% CI. Heterogeneity was assessed by chi(2) tests and quantified by I(2). Meta-regression models identified dose threshold and independent predictors of effects.

RESULTS

Sixteen trials (236 subjects) met the eligibility criteria. Isocaloric fructose exchange for carbohydrate raised triglycerides and lowered total cholesterol under specific conditions without affecting LDL cholesterol or HDL cholesterol. A triglyceride-raising effect without heterogeneity was seen only in type 2 diabetes when the reference carbohydrate was starch (mean difference 0.24 [95% CI 0.05-0.44]), dose was >60 g/day (0.18 [0.00-0.37]), or follow-up was < or =4 weeks (0.18 [0.00-0.35]). Piecewise meta-regression confirmed a dose threshold of 60 g/day (R(2) = 0.13)/10% energy (R(2) = 0.36). A total cholesterol-lowering effect without heterogeneity was seen only in type 2 diabetes under the following conditions: no randomization and poor study quality (-0.19 [-0.34 to -0.05]), dietary fat >30% energy (-0.33 [-0.52 to -0.15]), or crystalline fructose (-0.28 [-0.47 to -0.09]). Multivariate meta-regression analyses were largely in agreement.

CONCLUSIONS

Pooled analyses demonstrated conditional triglyceride-raising and total cholesterol-lowering effects of isocaloric fructose exchange for carbohydrate in type 2 diabetes. Recommendations and large-scale future trials need to address the heterogeneity in the data.

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.

Fructose modifies the hormonal response and modulates lipid metabolism during aerobic exercise after glucose supplementation

The metabolic response when aerobic exercise is performed after the ingestion of glucose plus fructose is unclear. In the present study, we administered two beverages containing GluF (glucose+fructose) or Glu (glucose alone) in a randomized cross-over design to 20 healthy aerobically trained volunteers to compare the hormonal and lipid responses provoked during aerobic exercise and the recovery phase. After ingesting the beverages and a 15-min resting period, volunteers performed 30 min of moderate aerobic exercise. Urinary and blood samples were taken at baseline (t(-15)), during the exercise (t(0), t(15) and t(30)) and during the recovery phase (t(45), t(75) and t(105)). Plasma insulin concentrations were higher halfway through the exercise period and during acute recuperation (t(15) and t(75); P<0.05) following ingestion of GluF than after Glu alone, without any differences between the effects of either intervention on plasma glucose concentrations. Towards the end of the exercise period, urinary catecholamine concentrations were lower following GluF (t(45); P<0.05). Plasma triacylglycerol (triglyceride) concentrations were higher after the ingestion of GluF compared with Glu (t(15), t(30), t(45) and t(105); P<0.05). Furthermore, with GluF, we observed higher levels of lipoperoxides (t(15), t(30), t(45) and t(105); P<0.05) and oxidized LDL (low-density lipoprotein; t(30); P<0.05) compared with after the ingestion of Glu alone. In conclusion, hormonal and lipid alterations are provoked during aerobic exercise and recovery by the addition of a dose of fructose to the pre-exercise ingestion of glucose.

Ingestion of black chokeberry fruit extract leads to intestinal and systemic changes in a rat model of prediabetes and hyperlipidemia

This report presents a complex analysis of changes proceeding in the gut, blood and internal organs of rats with induced oxidative stress, glucose intolerance and hyperlipidemia after dietary supplementation with an extract from black chokeberry (Aronia melanocarpa) fruit, that is a condensed source of polyphenols (714 mg/g), especially anthocyanin glycosides (56.6%). The disturbances mimicking those observed in metabolic syndrome were induced by a high-fructose diet and simultaneous single injection of streptozotocin (20 mg/kg). Dietary supplementation with the chokeberry fruit extract (0.2%) decreased activity of maltase and sucrase as well as increased activity of lactase in the mucosa of the small intestine. Its ingestion led also to the improvement of antioxidant status, especially, the concentration of a lipid peroxidation indicator (TBARS) in organ tissues (liver, kidney and lung) was normalized; some cholesterol-lowering and distinct hypoglycemic actions were also observed. The mechanism of glucose reduction is likely to be multifactorial, and we suggest the factors related with the decreased activity of mucosal disaccharidases important for further investigation. In conclusion, chokeberry fruit derivatives may act as a promising supplementary therapeutic option in the prevention and treatment of disorders occurring in metabolic syndrome, as well as their complications.

Fructose intolerance in children presenting with abdominal pain

OBJECTIVES

We determined the occurrence of fructose malabsorption in pediatric patients with previous diagnoses of abdominal pain caused by a functional bowel disorder, whether the restriction of fructose intake changes the reporting of symptoms, the role of fructose dosage, and the severity of resultant symptoms.

PATIENTS AND METHODS

We administered a fructose breath test to children presenting with persistent unexplained abdominal pain. Patients randomly received 1, 15, or 45 g fructose, and breath hydrogen was measured for 3 hours after ingestion. Test results were positive when breath hydrogen was 20 ppm greater than baseline and was accompanied by gastrointestinal symptoms.

RESULTS

A total of 32 patients was enrolled, and none of the 9 who received 1 g had positive results. Three of 10 who received 15 g and 8 of 13 who received 45 g had positive results. All patients with positive test results restricted their fructose intake. Among the group with positive results, 9 of 11 had rapid improvement of their gastrointestinal symptoms. After 2 months, all 9 patients continued to report improvement.

CONCLUSIONS

We concluded that fructose malabsorption may be a significant problem in children and that management of dietary intake can be effective in reducing gastrointestinal symptoms.

Fructose intolerance in IBS and utility of fructose-restricted diet

INTRODUCTION

Whether dietary fructose intolerance causes symptoms of irritable bowel syndrome (IBS) is unclear. We examined the prevalence of fructose intolerance in IBS and long-term outcome of fructose-restricted diet.

METHODS

Two hundred and nine patients with suspected IBS were retrospectively evaluated for organic illnesses. Patients with IBS (Rome II) and positive fructose breath test received instructions regarding fructose-restricted diet. One year later, their symptoms, compliance with, and effects of dietary modification on lifestyle were assessed using a structured interview.

RESULTS

Eighty patients (m/f=26/54) fulfilled Rome II criteria. Of 80 patients, 31 (38%) had positive breath test. Of 31 patients, 26 (84%) participated in follow-up (mean=13 mo) evaluation. Of 26 patients, 14 (53%) were compliant with diet; mean compliance=71%. In this group, pain, belching, bloating, fullness, indigestion, and diarrhea improved (P<0.02). Of 26 patients, 12 (46%) were noncompliant, and their symptoms were unchanged, except belching. The mean impact on lifestyle, compliant versus noncompliant groups was 2.93 versus 2.57 (P>0.05).

CONCLUSIONS

About one-third of patients with suspected IBS had fructose intolerance. When compliant, symptoms improved on fructose-restricted diet despite moderate impact on lifestyle; noncompliance was associated with persistent symptoms. Fructose intolerance is another jigsaw piece of the IBS puzzle that may respond to dietary modification.

Fructose malabsorption may be gender dependent and fails to show compensation by colonic adaptation

Fructose malabsorption is linked to gastrointestinal and other unusual symptoms. Polymers of fructose are also recognized prebiotics. While some prebiotics can self-adapt when consumed regularly (resulting in decreased breath hydrogen and symptoms), we wondered whether self-adaptation occurs with basic fructose. We evaluated 90 subjects (61 females). Each completed a diet questionnaire and underwent a fructose challenge. Breath hydrogen and quantified symptom scores were recorded. Group comparisons for sum of breath hydrogen and total symptom scores were evaluated with the Mann-Whitney U test. Spearman's correlation coefficient and chi(2) or Fisher's exact test were used as appropriate. Malabsorption occurred in 29 patients (32.2%) and low-grade symptoms without malabsorption in 30 (33%). Women complained of symptoms more frequently (p = 0.04) and exhibited more fructose malabsorption (p = 0.0527). Breath hydrogen correlated with symptoms (r = 0.516, p = 0.0037). Adaptation with increasing pretest fructose intake was absent. We conclude that gender may influence fructose malabsorption and there is no adaptation to regular consumption.

Effects of five different alcoholic drinks on patients with Crohn's disease

OBJECTIVE

Many patients with Crohn's disease (CD) complain of abdominal discomfort after alcohol intake. The aim of the present study was to investigate the effect of ethanol and sugar content in five different alcoholic drinks on abdominal discomfort in patients with CD.

MATERIAL AND METHODS

In a crossover study, two weeks apart, 12 healthy individuals and 20 patients with CD in remission consumed randomly red wine, white wine, Smirnoff Ice, Elephant Beer and pure ethanol. Blood samples were obtained for determination of serum ethanol and plasma glucose at 0, 30, 60, 90, 120 and 180 min. A self-reported pain symptom score was used.

RESULTS

There was no difference between CD patients and healthy individuals in the area under the curve (AUC) for the ethanol concentration after intake of the five different drinks. The plasma AUC for glucose in the CD patients after intake of Smirnoff Ice and Elephant beer was significantly increased (p<0.05) in comparison with that in the remaining three alcoholic drinks. Abdominal pain manifestations were significantly more pronounced in CD patients following intake of Smirnoff Ice and Elephant beer, with their higher sugar concentration, compared with intake of the remaining three drinks (p<0.05).

CONCLUSIONS

The present study shows no difference in alcohol absorption between CD patients and controls. The alcoholic drinks Smirnoff Ice and Elephant beer have an increased effect on self-reported abdominal pain in CD patients, probably due to the high sugar content in these drinks.

Ability of the normal human small intestine to absorb fructose: evaluation by breath testing

BACKGROUND & AIMS

Fructose consumption is increasing, and its malabsorption causes common gastrointestinal symptoms. Because its absorption capacity is poorly understood, there is no standard method of assessing fructose absorption. We performed a dose-response study of fructose absorption in healthy subjects to develop a breath test to distinguish normal from abnormal fructose absorption capacity.

METHODS

In a double-blind study, 20 healthy subjects received 10% solutions of 15, 25, and 50 g of fructose and 33% solution of 50-g fructose on 4 separate days at weekly intervals. Breath samples were assessed for hydrogen (H2) and methane (CH4) during a period of 5 hours, and symptoms were recorded.

RESULTS

No subject tested positive with 15 g. Two (10%) tested positive with 25 g fructose but were asymptomatic. Sixteen (80%) tested positive with 50 g (10% solution), and 11 (55%) had symptoms. Breath H2 was elevated in 13 (65%), CH4 in 1 (5%), and both in 2 (10%). Twelve (60%) tested positive with 50 g (33% solution), and 9 (45%) experienced symptoms. The area under the curve for H2 and CH4 was higher (P < .01) with 50 g compared with lower doses. There were no gender differences.

CONCLUSIONS

Healthy subjects have the capacity to absorb up to 25 g fructose, whereas many exhibit malabsorption and intolerance with 50 g fructose. Hence, we recommend 25 g as the dose for testing subjects with suspected fructose malabsorption. Breath samples measured for H2 and CH4 concentration at 30-minute intervals and for 3 hours will detect most subjects with fructose malabsorption.

Fructose malabsorption and symptoms of irritable bowel syndrome: guidelines for effective dietary management

Dietary fructose induces abdominal symptoms in patients with fructose malabsorption, but there are no published guidelines on its dietary management. The objective was to retrospectively evaluate a potentially successful diet therapy in patients with irritable bowel syndrome and fructose malabsorption. Tables detailing the content of fructose and fructans in foods were constructed. A dietary strategy comprising avoidance of foods containing substantial free fructose and short-chain fructans, limitation of the total dietary fructose load, encouragement of foods in which glucose was balanced with fructose, and co-ingestion of free glucose to balance excess free fructose was devised. Sixty-two consecutively referred patients with irritable bowel syndrome and fructose malabsorption on breath hydrogen testing underwent dietary instruction. Dietary adherence and effect on abdominal symptoms were evaluated via telephone interview 2 to 40 months (median 14 months) later. Response to the diet was defined as improvement of all symptoms by at least 5 points on a -10- to 10-point scale. Forty-eight patients (77%) adhered to the diet always or frequently. Forty-six (74%) of all patients responded positively in all abdominal symptoms. Positive response overall was significantly better in those adherent than nonadherent (85% vs 36%; P<0.01), as was improvement in individual symptoms (P<0.01 for all symptoms). This comprehensive fructose malabsorption dietary therapy achieves a high level of sustained adherence and good symptomatic response.

Functional bowel disorders

Employing a consensus approach, our working team critically considered the available evidence and multinational expert criticism, revised the Rome II diagnostic criteria for the functional bowel disorders, and updated diagnosis and treatment recommendations. Diagnosis of a functional bowel disorder (FBD) requires characteristic symptoms during the last 3 months and onset > or =6 months ago. Alarm symptoms suggest the possibility of structural disease, but do not necessarily negate a diagnosis of an FBD. Irritable bowel syndrome (IBS), functional bloating, functional constipation, and functional diarrhea are best identified by symptom-based approaches. Subtyping of IBS is controversial, and we suggest it be based on stool form, which can be aided by use of the Bristol Stool Form Scale. Diagnostic testing should be guided by the patient's age, primary symptom characteristics, and other clinical and laboratory features. Treatment of FBDs is based on an individualized evaluation, explanation, and reassurance. Alterations in diet, drug treatment aimed at predominant symptoms, and psychotherapy may be beneficial.