Prebiotic effects: metabolic and health benefits

The different compartments of the gastrointestinal tract are inhabited by populations of micro-organisms. By far the most important predominant populations are in the colon where a true symbiosis with the host exists that is a key for well-being and health. For such a microbiota, 'normobiosis' characterises a composition of the gut 'ecosystem' in which micro-organisms with potential health benefits predominate in number over potentially harmful ones, in contrast to 'dysbiosis', in which one or a few potentially harmful micro-organisms are dominant, thus creating a disease-prone situation. The present document has been written by a group of both academic and industry experts (in the ILSI Europe Prebiotic Expert Group and Prebiotic Task Force, respectively). It does not aim to propose a new definition of a prebiotic nor to identify which food products are classified as prebiotic but rather to validate and expand the original idea of the prebiotic concept (that can be translated in 'prebiotic effects'), defined as: 'The selective stimulation of growth and/or activity(ies) of one or a limited number of microbial genus(era)/species in the gut microbiota that confer(s) health benefits to the host.' Thanks to the methodological and fundamental research of microbiologists, immense progress has very recently been made in our understanding of the gut microbiota. A large number of human intervention studies have been performed that have demonstrated that dietary consumption of certain food products can result in statistically significant changes in the composition of the gut microbiota in line with the prebiotic concept. Thus the prebiotic effect is now a well-established scientific fact. The more data are accumulating, the more it will be recognised that such changes in the microbiota's composition, especially increase in bifidobacteria, can be regarded as a marker of intestinal health. The review is divided in chapters that cover the major areas of nutrition research where a prebiotic effect has tentatively been investigated for potential health benefits. The prebiotic effect has been shown to associate with modulation of biomarkers and activity(ies) of the immune system. Confirming the studies in adults, it has been demonstrated that, in infant nutrition, the prebiotic effect includes a significant change of gut microbiota composition, especially an increase of faecal concentrations of bifidobacteria. This concomitantly improves stool quality (pH, SCFA, frequency and consistency), reduces the risk of gastroenteritis and infections, improves general well-being and reduces the incidence of allergic symptoms such as atopic eczema. Changes in the gut microbiota composition are classically considered as one of the many factors involved in the pathogenesis of either inflammatory bowel disease or irritable bowel syndrome. The use of particular food products with a prebiotic effect has thus been tested in clinical trials with the objective to improve the clinical activity and well-being of patients with such disorders. Promising beneficial effects have been demonstrated in some preliminary studies, including changes in gut microbiota composition (especially increase in bifidobacteria concentration). Often associated with toxic load and/or miscellaneous risk factors, colon cancer is another pathology for which a possible role of gut microbiota composition has been hypothesised. Numerous experimental studies have reported reduction in incidence of tumours and cancers after feeding specific food products with a prebiotic effect. Some of these studies (including one human trial) have also reported that, in such conditions, gut microbiota composition was modified (especially due to increased concentration of bifidobacteria). Dietary intake of particular food products with a prebiotic effect has been shown, especially in adolescents, but also tentatively in postmenopausal women, to increase Ca absorption as well as bone Ca accretion and bone mineral density. Recent data, both from experimental models and from human studies, support the beneficial effects of particular food products with prebiotic properties on energy homaeostasis, satiety regulation and body weight gain. Together, with data in obese animals and patients, these studies support the hypothesis that gut microbiota composition (especially the number of bifidobacteria) may contribute to modulate metabolic processes associated with syndrome X, especially obesity and diabetes type 2. It is plausible, even though not exclusive, that these effects are linked to the microbiota-induced changes and it is feasible to conclude that their mechanisms fit into the prebiotic effect. However, the role of such changes in these health benefits remains to be definitively proven. As a result of the research activity that followed the publication of the prebiotic concept 15 years ago, it has become clear that products that cause a selective modification in the gut microbiota's composition and/or activity(ies) and thus strengthens normobiosis could either induce beneficial physiological effects in the colon and also in extra-intestinal compartments or contribute towards reducing the risk of dysbiosis and associated intestinal and systemic pathologies

What health care for undocumented migrants in Belgium?

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Desarrollo y evaluación de un cuestionario semi-cuantitativo de frecuencias alimenticias para adolescentes bolivianos

Introduction: Since previous studies suggest that the dietary patterns and lifestyle in adolescence have an impact in health later in life, it is pertinent to monitor and document their dietary patterns. Objective: To develop and test the reliability and validity of a semi-quantitative food frequency questionnaire for Bolivian adolescents. Setting: La Paz, September - October 2004. Methodology: A convenience sample of 82 students from a secondary participated in the study. A semi quantitative food frequency questionnaire was applied twice with one month interval (Q1 and Q2). A 3 days dietary record (3R) was obtained from 32 of the Students as standard. Results: Most of the questions (87%) reporting intake of each individual food item agreed moderately to substantially while only 2 individual food items fell into the category of slight agreement and 11 into the category of fair agreement using the kappa statistic. Quantities obtained from both applications of the questionnaire yielded similar results (P > 0.05). Nutrient estimates obtained from the Q1 and Q2 and the 3R were not statistically different (P > 0.05). Conclusion: The semi - quantitative food frequency questionnaire is apparently reliable and valid for the measurement of absolute food intake in Bolivian adolescents. Care will be taken in the future to prevent overestimation of intake measured by this particular questionnaire

FabR regulates Salmonella biofilm formation via its direct target FabB

Background: Biofilm formation is an important survival strategy of Salmonella in all environments. By mutant screening, we showed a knock-out mutant of fabR, encoding a repressor of unsaturated fatty acid biosynthesis (UFA), to have impaired biofilm formation. In order to unravel how this regulator impinges on Salmonella biofilm formation, we aimed at elucidating the S. Typhimurium FabR regulon. Hereto, we applied a combinatorial high-throughput approach, combining ChIP-chip with transcriptomics. Results: All the previously identified E. coli FabR transcriptional target genes (fabA, fabB and yqfA) were shown to be direct S. Typhimurium FabR targets as well. As we found a fabB overexpressing strain to partly mimic the biofilm defect of the fabR mutant, the effect of FabR on biofilms can be attributed at least partly to FabB, which plays a key role in UFA biosynthesis. Additionally, ChIP-chip identified a number of novel direct FabR targets (the intergenic regions between hpaR/hpaG and ddg/ydfZ) and yet putative direct targets (i.a. genes involved in tRNA metabolism, ribosome synthesis and translation). Next to UFA biosynthesis, a number of these direct targets and other indirect targets identified by transcriptomics (e.g. ribosomal genes, ompA, ompC, ompX, osmB, osmC, sseI), could possibly contribute to the effect of FabR on biofilm formation. Conclusion: Overall, our results point at the importance of FabR and UFA biosynthesis in Salmonella biofilm formation and their role as potential targets for biofilm inhibitory strategies

Ageing, immunity and influenza: a role for probiotics?

Influenza is a major cause of death in the over 65s. Increased susceptibility to infection and reduced response to vaccination are due to immunosenscence in combination with medical history and lifestyle factors. Age-related alterations in the composition of the gut microbiota have a direct impact on the immune system and it is proposed that modulation of the gut microbiota using pre- and probiotics could offer an opportunity to improve immune responses to infections and vaccination in older people. There is growing evidence that pro- biotics have immunomodulatory properties, which to some extent are strain-dependent, and are strongly influenced by ageing. Randomised controlled trials suggest that probiotics may reduce the incidence and/or severity of respiratory infections, although there is limited data on older people. A small number of studies have examined the potential adjuvant effects of selected probiotics for vaccination against influenza; however, the data is inconsistent, particularly in older people. This review describes the impact of age-related changes in the gut on the immune response to respiratory infections and evaluates whether restoration of gut microbial homoeostasis by probiotics offers an opportunity to modulate the outcome of respiratory infections and vaccination against influenza in older people. Although there is promising evidence for effects of probiotics on human health, there is a lack of consistent data, perhaps partly due to strain-specific differences and an influence of the age of the host. Further research is critical in evaluating the potential use of probiotics in respiratory infections and vaccination in the ageing population

Severe acute malnutrition and mortality in children in the community : Comparison of indicators in a multi-country pooled analysis

Funding: The authors received no specific funding for this work. Competing interests: The authors have declared that no competing interests exist. Acknowledgments We would like to acknowledge the principal investigators of the original studies: Jan Van den Broeck for the DRC cohort, Michel Garenne for the Senegal cohort, and Keith West for the Nepal cohort. The DRC study was supported by the Centre de Développement Intégrale–Bwamanda, and funding was provided by the Flemish Inter-University Council (Vlaamse Interuniversitaire Raad), the Belgian Administration for Development Cooperation, and the Nutricia Research Foundation. Catherine Schwinger is affiliated to the Centre for Intervention Science in Maternal and Child Health (CISMAC), which is funded by the Research Council of Norway through its Centres of Excellence funding scheme (project number 223269), the University of Bergen (UiB), Norway.Peer reviewedPublisher PD

Inconsistent diagnosis of acute malnutrition by weight-for-height and mid-upper arm circumference : contributors in 16 cross-sectional surveys from South Sudan, the Philippines, Chad, and Bangladesh

Background: The two anthropometric indicators of acute malnutrition in children under 5 years, i.e. a Mid-Upper Arm Circumference < 125 mm (MUAC(125)) or a Weight-for-Height Z-score<-2 (WHZ(-2)), correlate poorly. We aimed at assessing the contribution of age, sex, stunting (Height-for-Age HAZ<-2), and low sitting-standing height ratio Z-score (SSRZ in the 1st tertile of the study population, called hereafter 'longer legs') to this diagnosis discrepancy. Methods: Data from 16 cross-sectional nutritional surveys carried out by Action Against Hunger International in South Sudan, the Philippines, Chad, and Bangladesh fed multilevel, multivariate regression models, with either WHZ -2 or MUAC(125) as the dependent variable and age, sex, stunting, and 'longer legs' as the independent ones. We also compared how the performance of MUAC125 and WHZ-2 to detect slim children, i.e. children with a low Weight-for-Age (WAZ=-2), was modified by the contributors. Results: Overall 23.1 % of the 14,409 children were identified as acutely malnourished by either WHZ-2 or MUAC125, but only 28.5 % of those (949/3,328) were identified by both indicators. Being stunted (+17.8 %; 95 % CI: 14.8 %; 22.8 %), being a female (+16.5 %; 95 % CI: 13.5 %; 19.5 %) and being younger than 24 months (+33.6 %; 95 % CI: 30.4 %; 36.7 %) were factors strongly associated with being detected as malnourished by MUAC125 and not by WHZ-2, whereas having 'longer legs' moderately increased the diagnosis by WHZ-2 (+4.2 %; 95 % CI: 0.7 %; 7.6 %). The sensitivity to detect slim children by MUAC125 was 31.0 % (95 % CI: 26.8 %; 35.2 %) whereas it was 70.6 % (95 % CI: 65.4 %; 75.9 %) for WHZ-2. The sensitivity of MUAC125 was particularly affected by age (57.4 % vs. 18.1 % in children aged = 24 months). Specificity was high for both indicators. Conclusions: MUAC125 should not be used as a stand-alone criterion of acute malnutrition given its strong association with age, sex and stunting, and its low sensitivity to detect slim children. Having 'longer legs' moderately increases the diagnosis of acute malnutrition by WHZ-2. Prospective studies are urgently needed to elucidate the clinical and physiological outcomes of the various anthropometric indicators of malnutrition