Intrinsic dietary fibers and the gut microbiome: Rediscovering the benefits of the plant cell matrix for human health

Abstract

Dietary fibers contribute to structure and storage reserves of plant foods and fundamentally impact human health, partly by involving the intestinal microbiota, notably in the colon. Considerable attention has been given to unraveling the interaction between fiber type and gut microbiota utilization, focusing mainly on single, purified fibers. Studying these fibers in isolation might give us insights into specific fiber effects, but neglects how dietary fibers are consumed daily and impact our digestive tract: as intrinsic structures that include the cell matrix and content of plant tissues. Like our ancestors we consume fibers that are entangled in a complex network of plants cell walls that further encapsulate and shield intra-cellular fibers, such as fructans and other components from immediate breakdown. Hence, the physiological behavior and consequent microbial breakdown of these intrinsic fibers differs from that of single, purified fibers, potentially entailing unexplored health effects. In this mini-review we explain the difference between intrinsic and isolated fibers and discuss their differential impact on digestion. Subsequently, we elaborate on how food processing influences intrinsic fiber structure and summarize available human intervention studies that used intrinsic fibers to assess gut microbiota modulation and related health outcomes. Finally, we explore current research gaps and consequences of the intrinsic plant tissue structure for future research. We postulate that instead of further processing our already (extensively) processed foods to create new products, we should minimize this processing and exploit the intrinsic health benefits that are associated with the original cell matrix of plant tissues.

Weighted Gene Co-Expression Network Analysis Identifies a Functional Guild and Metabolite Cluster Mediating the Relationship between Mucosal Inflammation and Adherence to the Mediterranean Diet in Ulcerative Colitis

“…Whole food, plant-based diet interventions, such as the MD are interesting and represent how humans normally eat, as humans do not consume fiber as an isolated component. Vegetables, fruit, nuts, seeds, legumes, and grains are whole foods that are not just one single source or extract of fiber but contain a complex three-dimensional plant cell matrix (i.e., plant cell walls), termed “intrinsic fibers” [ 65 ]. Various types of fiber are stored in vacuoles (e.g., starch, fructans, sugars, and phytochemicals) within the plant cell walls, which differ according to the plant source.…”

“…Various types of fiber are stored in vacuoles (e.g., starch, fructans, sugars, and phytochemicals) within the plant cell walls, which differ according to the plant source. As a result, the three-dimensional plant cell matrix has important consequences for the microbiota in accessing the individual fibers, influencing digestion and fermentation patterns [ 65 ]. Although there is a paucity of human clinical trials that have examined the association of intrinsic fibers and the gut microbiome, increased levels of health-associated microbial taxa involved in the breakdown of fiber, are observed [ 65 ].…”

“…As a result, the three-dimensional plant cell matrix has important consequences for the microbiota in accessing the individual fibers, influencing digestion and fermentation patterns [ 65 ]. Although there is a paucity of human clinical trials that have examined the association of intrinsic fibers and the gut microbiome, increased levels of health-associated microbial taxa involved in the breakdown of fiber, are observed [ 65 ]. In the current study, the three main bacteria taxa identified in the health-associated microbiome guild ( Figure 8 A) are known to metabolize a variety of fibers; F. prausnitzii and R. inulinivorans ferment β-fructans, including inulin, along with galactooligosaccharides and xylooligosaccharides, while D. longicatena is stimulated by short-chain fructooligosaccharides [ 66 , 67 , 68 ].…”

Gut microbiome-modulated dietary strategies in EAE and multiple sclerosis

“…These studies support dietary fibers as potent modulators of EAE and potential protective or therapeutic supplements for MS patients. A more detailed discussion of dietary fibers and their impact on the gut microbiome was recently reviewed by others ( 54 ).…”

Beyond purified dietary fibre supplements: Compositional variation between cell wall fibre from different plants influences human faecal microbiota activity and growth in vitro

“…To date, the majority of research investigating the effect of dietary fibre on the gut microbiota has focused on purified carbohydrates (Gibson et al, 2017) and less is known on how complex insoluble fibre affects bacterial growth and community composition (de Paepe et al, 2019; Puhlmann & de Vos, 2022). The cell wall composition varies between plants, in particular between grains (type II, rich in arabinoxylan and β‐glucan) and non‐grains (type I, rich in pectin and xyloglucan) (Fry, 2018).…”