The development of the concept of dietary fibre

Hyperkalemia and Plant-Based Diets in Chronic Kidney Disease

Traditional dietary guidelines for patients with kidney disease recommend restriction of plant foods due to concerns about hyperkalemia and associated adverse events. Studies conducted over several decades have shown that the basis for these guidelines does not match the evidence. Serum potassium levels can be elevated in patients with reduced kidney function after consumption of foods with potassium-based additives or with highly concentrated potassium content such as juices, dried fruit, or purees. However, plant foods may have certain qualities that may blunt potassium retention including their alkalinizing effects, the lack of bioavailable potassium, and the impact of dietary fiber in organic plant foods on colonic potassium excretion. Furthermore, there are many benefits of plant foods that patients with kidney disease may be missing by excluding them from their diets by recommending the historical low-potassium "renal diet." Revised dietary recommendations for kidney health may encourage patient-centered kidney recipes that revolve around plant foods and do not restrict them.

Interactions between dietary fibre and the gut microbiota

Research characterising the gut microbiota in different populations and diseases has mushroomed since the advent of next-generation sequencing techniques. However, there has been less emphasis on the impact of dietary fibres and other dietary components that influence gut microbial metabolic activities. Dietary fibres are the main energy source for gut bacteria. However, fibres differ in their physicochemical properties, their effects on the gut and their fermentation characteristics. The diversity of carbohydrates and associated molecules in fibre-rich foods can have a major influence on microbiota composition and production of bioactive molecules, for example SCFAs and phenolic acids. Several of these microbial metabolites may influence the functions of body systems including the gut, liver, adipose tissues and brain. Dietary fibre intake recommendations have recently been increased (to 30 g daily) in response to growing obesity and other health concerns. Increasing intakes of specific fibre and plant food sources may differentially influence the bacteria and their metabolism. However, in vitro studies show great individual variability in the response of the gut microbiota to different fibres and fibre combinations, making it difficult to predict which foods or food components will have the greatest impact on levels of bioactive molecules produced in the colon of individuals. Greater understanding of individual responses to manipulation of the diet, in relation to microbiome composition and production of metabolites with proven beneficial impact on body systems, would allow the personalised approach needed to best promote good health.

Dietary Fibre Consensus from the International Carbohydrate Quality Consortium (ICQC)

Dietary fibre is a generic term describing non-absorbed plant carbohydrates and small amounts of associated non-carbohydrate components. The main contributors of fibre to the diet are the cell walls of plant tissues, which are supramolecular polymer networks containing variable proportions of cellulose, hemicelluloses, pectic substances, and non-carbohydrate components, such as lignin. Other contributors of fibre are the intracellular storage oligosaccharides, such as fructans. A distinction needs to be made between intrinsic sources of dietary fibre and purified forms of fibre, given that the three-dimensional matrix of the plant cell wall confers benefits beyond fibre isolates. Movement through the digestive tract modifies the cell wall structure and may affect the interactions with the colonic microbes (e.g., small intestinally non-absorbed carbohydrates are broken down by bacteria to short-chain fatty acids, absorbed by colonocytes). These aspects, combined with the fibre associated components (e.g., micronutrients, polyphenols, phytosterols, and phytoestrogens), may contribute to the health outcomes seen with the consumption of dietary fibre. Therefore, where possible, processing should minimise the degradation of the plant cell wall structures to preserve some of its benefits. Food labelling should include dietary fibre values and distinguish between intrinsic and added fibre. Labelling may also help achieve the recommended intake of 14 g/1000 kcal/day.

Establishing What Constitutes a Healthy Human Gut Microbiome: State of the Science, Regulatory Considerations, and Future Directions

On December 17, 2018, the North American branch of the International Life Sciences Institute (ILSI North America) convened a workshop "Can We Begin to Define a Healthy Gut Microbiome Through Quantifiable Characteristics?" with >40 invited academic, government, and industry experts in Washington, DC. The workshop objectives were to 1) develop a collective expert assessment of the state of the evidence on the human gut microbiome and associated human health benefits, 2) see if there was sufficient evidence to establish measurable gut microbiome characteristics that could serve as indicators of "health," 3) identify short- and long-term research needs to fully characterize healthy gut microbiome-host relationships, and 4) publish the findings. Conclusions were as follows: 1) mechanistic links of specific changes in gut microbiome structure with function or markers of human health are not yet established; 2) it is not established if dysbiosis is a cause, consequence, or both of changes in human gut epithelial function and disease; 3) microbiome communities are highly individualized, show a high degree of interindividual variation to perturbation, and tend to be stable over years; 4) the complexity of microbiome-host interactions requires a comprehensive, multidisciplinary research agenda to elucidate relationships between gut microbiome and host health; 5) biomarkers and/or surrogate indicators of host function and pathogenic processes based on the microbiome need to be determined and validated, along with normal ranges, using approaches similar to those used to establish biomarkers and/or surrogate indicators based on host metabolic phenotypes; 6) future studies measuring responses to an exposure or intervention need to combine validated microbiome-related biomarkers and/or surrogate indicators with multiomics characterization of the microbiome; and 7) because static genetic sampling misses important short- and long-term microbiome-related dynamic changes to host health, future studies must be powered to account for inter- and intraindividual variation and should use repeated measures within individuals.

Marine polysaccharides attenuate metabolic syndrome by fermentation products and altering gut microbiota: An overview

Marine polysaccharides (MPs), including plant, animal, and microbial-derived polysaccharides, can alleviate metabolic syndrome (MetS) by different regulation mechanisms. MPs and their derivatives can attenuate MetS by vary cellular signal pathways, such as peroxisome proliferator-activated receptor, 5' adenosine monophosphate-activated protein kinase, and CCAAT/enhancer binding protein-α. Also, most of MPs cannot be degraded by human innate enzymes, but they can be degraded and fermented by human gut microbiota. The final metabolic products of these polysaccharides are usually short-chain fatty acids (SCFAs), which can change the gut microbiota ecology by altering the existing percentage of special microorganisms. In addition, the SCFAs and changed gut microbiota can regulate enteroendocrine hormone secretion, blood glucose, lipid metabolism levels, and other MetS symptoms. Here, we summarize the up-to-date findings on the effects of MPs, particularly marine microbial-derived polysaccharides, and their metabolites on attenuating MetS.

Dietary Fiber Analysis of Four Pulses Using AOAC 2011.25: Implications for Human Health

Chickpeas, common beans, dry peas, and lentils are pulse crops that have been a cornerstone of the human diet since the inception of agriculture. However, the displacement of pulses from the diet by low fiber protein alternatives has resulted in a pervasive deficiency referred to as the dietary fiber gap. Using an analytical method American Association of Analytical Chemists (AOAC) 2011.25 that conforms to the Codex Alimentarius Commission consensus definition for dietary fiber, the fiber content of these pulse crops was evaluated in seed types used for commercial production. These pulse crops have 2 to 3 times more fiber per 100 g edible portion than other dietary staples. Moreover, there is marked variation in fiber content among cultivars of the same crop. We conclude that pulse crop consumption should be emphasized in efforts to close the dietary fiber gap. The substantial differences in fiber content among currently available cultivars within a crop can be used to further improve gains in fiber intake without the need to change dietary habits. This provides a rationale for cultivar-based food labeling.

Starving our microbial self: the deleterious consequences of a diet deficient in microbiota-accessible carbohydrates

The gut microbiota of a healthy person may not be equivalent to a healthy microbiota. It is possible that the Western microbiota is actually dysbiotic and predisposes individuals to a variety of diseases. The asymmetric plasticity between the relatively stable human genome and the more malleable gut microbiome suggests that incompatibilities between the two could rapidly arise. The Western lifestyle, which includes a diet low in microbiota-accessible carbohydrates (MACs), has selected for a microbiota with altered membership and functionality compared to those of groups living traditional lifestyles. Interactions between resident microbes and host leading to immune dysregulation may explain several diseases that share inflammation as a common basis. The low-MAC Western diet results in poor production of gut microbiota-generated short-chain fatty acids (SCFAs), which attenuate inflammation through a variety of mechanisms in mouse models. Studies focused on modern and traditional societies, combined with animal models, are needed to characterize the connection between diet, microbiota composition, and function. Differentiating between an optimal microbiota, one that increases disease risk, and one that is causative or potentiates disease will be required to further understand both the etiology and possible treatments for health problems related to microbiota dysbiosis.

Dietary fiber supplements: effects in obesity and metabolic syndrome and relationship to gastrointestinal functions

Dietary fiber is a term that reflects a heterogeneous group of natural food sources, processed grains, and commercial supplements. Several forms of dietary fiber have been used as complementary or alternative agents in the management of manifestations of the metabolic syndrome, including obesity. Not surprisingly, there is a great variation in the biological efficacy of dietary fiber in the metabolic syndrome and body weight control. Diverse factors and mechanisms have been reported as mediators of the effects of dietary fiber on the metabolic syndrome and obesity. Among this array of mechanisms, the modulation of gastric sensorimotor influences appears to be crucial for the effects of dietary fiber but also quite variable. This report focuses on the role, mechanism of action, and benefits of different forms of fiber and supplements on obesity and the metabolic syndrome, glycemia, dyslipidemia, and cardiovascular risk and explores the effects of dietary fiber on gastric sensorimotor function and satiety in mediating these actions of dietary fiber.