Grain Fibre and Gut Health
Condition: Intestinal Disorder; Glucose Metabolism Disorders; Inflammation
MeSH terms: Intestinal Diseases; Metabolic Diseases; Glucose Metabolism Disorders; Inflammation
Study type: Interventional

Summary: 
      Wholegrain fibre is known to affect on the gut health, but also may cause intestinal
      discomfort. Thus, many individuals may avoid the consumption of whole grain cereals in spite
      of their known health benefits, and may in this regard consume more restricted diets. In the
      preset study the aim was to technologically modify the cereal fibres to improve its usability
      and to maintain its health beneficial properties. The objective was to investigate intestinal
      fermentation of grain dietary fibre and associated effects on gut-mediated metabolic health,
      such as immunological health and adipose tissue function. The hypothesis was that whole grain
      products maintain their original beneficial health effects and may be better tolerable when
      the bran is technologically modified. Additionally, it was hypothesized that gut-mediated
      bioavailability of plant cell wall compounds and their metabolites affect the metabolic
      health through their immunomodulatory effects.
    

Detailed description: 
      Cereal foods are the most important source of dietary fibre in the Northern European diet.
      Epidemiological studies have repeatedly shown that diets rich in whole grain foods reduce the
      risk of type 2 diabetes mellitus and cardiovascular disease. Cereal fibre complex has been
      suggested as one of the main constituents behind the protective effects. The dietary fibre
      complex is composed of biopolymers and small molecular weight compounds, that formulate the
      structure, content and interactions which change during processing. It has been proposed,
      based on animal data, that the shift in gut microbiota communities is a potential mechanism
      linking dietary fibre with reduced diabetes risk. Today it is known that gut microbita is
      actively interacting with dietary fibre producing active functional compounds to the
      circulation, and thus contribute to health benefits of dietary fibre. The hypothesis that
      insoluble fibre is a major contributor of the protective effects of whole-grain type cereal
      foods emphasizes the importance of dietary fibre structure and the conversions of both
      carbohydrates and polyphenols in the large intestine. The importance of structural features
      of grain foods in relation to their protective effect against type 2 diabetes was also
      pointed out in the previous review. On the other hand, soluble arabinoxylo-oligosaccharides
      have been shown to be selectively fermented by bifidobacteria in in vitro studies, and may
      thus also be health-protective.

      Large intestinal fermentation of the non-digested material causes both hydrolysis of the cell
      wall matrix and also liberation, further metabolism and absorption of the associated
      compounds, such as polyphenols. The interactions between dietary factors, gut microbiota and
      host metabolism are increasingly demonstrated to be important for maintaining homeostasis and
      health, but research into the role of fibre structure and phytochemicals in gut microbiota
      mediated signalling is in its early phases.The physiological effects of dietary fibre are
      dependent on the physico-chemical properties, which are mainly influenced by particle size,
      cell wall architecture, solubility, degree of polymerisation and substitution, distribution
      of side chains and degree of cross-linking of the polymers. Insoluble dietary fibres are
      generally more resistant to colonic fermentation than soluble dietary fibre. Solubility of
      dietary fibre has a major effect also on the bioavailability of fibre associated nutrients
      and phytochemicals. It has been showed in vitro that enzymatic solubilisation of insoluble
      dietary fibre stimulated the growth of bifidobacteria and lactobacilli. Additionally, it has
      been shown that the effect of wheat-bran derived arabinoxylo-oligosaccharides on SCFA
      production and bifidobacterial numbers in rat faeces depended on the average degree of
      polymerisation (avDP) of the AXOS preparations - the low avDP preparations increased colonic
      acetate and butyrate production and boosted the bifidobacteria, whereas the higher avDP
      preparation suppressed branched SCFA concentrations (a marker for protein fermentation).
      When, the prebiotic effect of whole-grain wheat and wheat bran breakfast cereals was compared
      in a human PCT, whole grain cereals proved to be more efficient prebiotics for bifidobacteria
      whereas ingestion of both products resulted in a significant increase in ferulic acid
      concentrations in blood.

      The objective is to investigate intestinal fermentation of grain dietary fibre and associated
      effects on gut-mediated metabolic health, such as immunological health and adipose tissue
      function. Part of the population, however, suffers from discomfort of gastrointestinal tract
      after consumption of whole grain products, especially rye. The hypothesis is that whole grain
      products maintain their original beneficial health effects and may be better tolerable when
      the bran is technologically modified. Moreover, it is hypothesized that gut-mediated
      bioavailability of plant cell wall compounds and their metabolites affect the metabolic
      health through their immunomodulatory effects.
    

Intervention name(s): Rye bran bread intervention; Rye bread intervention; Wheat bread diet
Intervention type(s): Other; Other; Other
Intervention description(s): 4 week dietary intervention rich in rye bran bread; 4 week dietary intervention rich in rye bread; 4 week dietary intervention rich in wheat bread as an active comparator for previous two interventions
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Single (Investigator)
Primary purpose: Other