Gut microbiome responses to dietary intake of grain-based fibers with the potential to modulate markers of metabolic disease: a systematic literature review

Diet-microbiota associations in gastrointestinal research: a systematic review

Interactions between diet and gastrointestinal microbiota influence health status and outcomes. Evaluating these relationships requires accurate quantification of dietary variables relevant to microbial metabolism, however current dietary assessment methods focus on dietary components relevant to human digestion only. The aim of this study was to synthesize research on foods and nutrients that influence human gut microbiota and thereby identify knowledge gaps to inform dietary assessment advancements toward better understanding of diet-microbiota interactions. Thirty-eight systematic reviews and 106 primary studies reported on human diet-microbiota associations. Dietary factors altering colonic microbiota included dietary patterns, macronutrients, micronutrients, bioactive compounds, and food additives. Reported diet-microbiota associations were dominated by routinely analyzed nutrients, which are absorbed from the small intestine but analyzed for correlation to stool microbiota. Dietary derived microbiota-relevant nutrients are more challenging to quantify and underrepresented in included studies. This evidence synthesis highlights advancements needed, including opportunities for expansion of food composition databases to include microbiota-relevant data, particularly for human intervention studies. These advances in dietary assessment methodology will facilitate translation of microbiota-specific nutrition therapy to practice.

Characteristics and properties of a polysaccharide isolated from Wolfiporia cocos as potential dietary supplement for IBS

Introduction

As low FODMAP (Fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet therapy is recommended for most of Irritable Bowel Syndrome (IBS) patients, the consequent insufficient of dietary fibers (DFs) intake exert an adverse impact on intestinal health. It is necessary to find suitable DFs for IBS patients.

Methods

This study extracted a water-insoluble polysaccharide from Wolfiporia cocos (WIP) by alkali-extraction and acid-precipitation method. Its molecular weight was detected by high performance gel permeation chromatography (HPGPC) analysis. The structure of WIP was analyzed by Fourier transform infrared (FT-IR) spectrum, Nuclear Magnetic Resonance (NMR) spectra and X-ray diffraction (XRD). The properties related to stability, digestion, viscosity, osmotic activity, adsorption and fermentation were investigated, aimed to explore the feasibility of WIP as a new DF supplement for patients with IBS. In addition, 16S rRNA sequencing analysis was conducted to explore its effects on IBS-related gut microbiota.

Results and Discussion

The results showed that WIP had a single homogeneous composition and the molecular weight was 8.1 × 103 Da. WIP was indicated as a kind of pyranose form with β anomeric configuration and the main chain of WIP was 1,3-β-glucan with amorphous structure. In addition to good thermal stability, WIP also has low bioavailability and can reach the colon mostly without being digested. Moreover, the low viscosity and osmotic activity, the high water- swelling and water/oil-holding capacity, fructose adsorption capacity and poor fermentation performance of WIP demonstrated that it is suitable for IBS patients. It is worth noting that WIP regulates IBS associated gut microbiota effectively, such as the abundance of Lachnospiraceae and Prevotella. These findings provide a theoretical basis for the development of WIP as a dietary supplement for IBS patients with low FODMAP diet therapy.

GRAPHICAL ABSTRACT

Gut health, the microbiome and dietary choices: An exploration of consumer perspectives

AIMS

To explore consumer perceptions regarding dietary behaviours related to the gut microbiome, to assist in effective translation of research to practice.

METHODS

Online focus groups were conducted (adults with no formal medical or nutrition training). Semi-structured open-ended questioning explored perspectives related to gut health and dietary behaviours. A qualitative descriptive analysis approach was undertaken in duplicate.

RESULTS

Fourteen focus groups were conducted (n = 38, 15 males, 23 females). Four overarching themes regarding consumer perceptions were identified. These were (a) gut health equates with wellbeing, (b) there are divergent perceptions of how diet influences gut health, (c) interest in scientific evidence does not necessarily influence dietary behaviour and (d) gastrointestinal symptoms influence dietary behaviour.

CONCLUSIONS

Consumers are interested in gut health and understand that diet may be important. Given that current literature regarding diet and gut health does not differ from dietary guidelines, consumer interest may provide a timely slant to promote longstanding guidelines. Consumer education to limit scepticism around government messaging, including utilisation of social media by nutrition professionals, may be key to improving adherence to guidelines.

Dietitians' perspectives on the role of dietetics practice in 'gut health'

AIMS

This study aimed to explore dietitians' perspectives on the evidence surrounding the relationship between diet and 'gut health' and the current and emerging role of dietetics practice in this area.

METHODS

A qualitative descriptive methodology was used. Online semi-structured interviews were conducted with Australian dietitians, focused on the perspectives related to gut health management in dietetics practice. Inductive thematic analysis was employed, commencing with initial coding by two researchers, and further coding leading to development of emergent themes. Divergent data were discussed and considered in analysis.

RESULTS

Fourteen interviews were conducted (2 males, 12 females). An overarching theme identified that current evidence is insufficient to direct dietetics practice change regarding gut health. Six subthemes on dietetics practice in 'gut health' emerged including (a) practice is multifaceted, (b) current practice aligns with dietary guidelines, (c) symptom management remains the primary concern, (d) evidence-based information is sought, (e) translational evidence is required for practice change and (f) there is a role for dietetics in gut health research and translation.

CONCLUSIONS

Dietitians do not appear confident in their practice regarding gut microbiome-related management and recognise there is currently limited translatable research to inform practice. Evidence to date suggests that recommendations for positive gut health do not differ substantially from Australian Dietary Guidelines. Dietitians will need additional education if further evidence emerges, however they demonstrated a strong commitment to evidence-based practice.