Re-evaluation of the mechanisms of dietary fibre and implications for macronutrient bioaccessibility, digestion and postprandial metabolism

Abstract

The positive effects of dietary fibre on health are now widely recognised; however, our understanding of the mechanisms involved in producing such benefits remains unclear. There are even uncertainties about how dietary fibre in plant foods should be defined and analysed. This review attempts to clarify the confusion regarding the mechanisms of action of dietary fibre and deals with current knowledge on the wide variety of dietary fibre materials, comprising mainly of NSP that are not digested by enzymes of the gastrointestinal (GI) tract. These non-digestible materials range from intact cell walls of plant tissues to individual polysaccharide solutions often used in mechanistic studies. We discuss how the structure and properties of fibre are affected during food processing and how this can impact on nutrient digestibility. Dietary fibre can have multiple effects on GI function, including GI transit time and increased digesta viscosity, thereby affecting flow and mixing behaviour. Moreover, cell wall encapsulation influences macronutrient digestibility through limited access to digestive enzymes and/or substrate and product release. Moreover, encapsulation of starch can limit the extent of gelatinisation during hydrothermal processing of plant foods. Emphasis is placed on the effects of diverse forms of fibre on rates and extents of starch and lipid digestion, and how it is important that a better understanding of such interactions with respect to the physiology and biochemistry of digestion is needed. In conclusion, we point to areas of further investigation that are expected to contribute to realisation of the full potential of dietary fibre on health and well-being of humans.

Fibrous Cellular Structures are Found in a Commercial Fruit Smoothie and Remain Intact during Simulated Digestion

“…Cell walls are natural structures that occur in plant foods that offer a natural barrier to molecular exchange and enzymatic digestion of cellular contents [18]. Most studies on cellular structures have focused on legumes and nuts which have relatively thick and rigid cell walls [21].…”

“…This method is widely used to investigate protein and lipid digestion, but has not yet been used in the context of fibre analysis. It has been recognised that typical methods of fibre analysis are not likely to reflect physiological function [18]. We postulate that cell wall structure has an effect on fibre measurement.…”

Extending in vitro digestion models to specific human populations: Perspectives, practical tools and bio-relevant information

“…Such insights include not just understanding of food breakdown but also its impact on gastro-intestinal functions, e.g. gastric emptying and intestinal motility, as detailed by others (Grundy et al, 2016;Houghton, Hickson, & Read, 1987;Meyer, Elashoff, & Lake, 1999;Sarosiek et al, 2010).…”

The Western Diet–Microbiome-Host Interaction and Its Role in Metabolic Disease

“…Acellular nutrients, i.e. nutrients not contained in cells, provide microbial and human cells with more easily digestible substrates [39] that influence human absorption kinetics [40][41][42] and are likely to influence intestinal bacterial growth [38].…”

“…The share of cellular nutrients that become accessible during digestion in the gut differs from food to food, depending on the nature of the food matrix and processing that will alter the properties of the outer cell [39]. Animal cells lack cell walls, and their phospholipid membranes are efficiently hydrolyzed by human digestive enzymes, liberating the cell content into the gut lumen [43].…”