Dietary fibers as beneficial microbiota modulators: A proposed classification by prebiotic categories

Dietary fiber is a group of heterogeneous substances that are neither digested nor absorbed in the small intestine. Some fibers can be classified as prebiotics if they are metabolized by beneficial bacteria present in the hindgut microbiota. The aim of this review was to specify the prebiotic properties of different subgroups of dietary fibers (resistant oligosaccharides, non-starch polysaccharides, resistant starches, and associated substances) to classify them by prebiotic categories. Currently, only resistant oligosaccharides (fructans [fructooligosaccharides, oligofructose, and inulin] and galactans) are well documented as prebiotics in the literature. Other fibers are considered candidates to prebiotics or have prebiotic potential, and apparently some have no prebiotic effect on humans. This dietary fiber classification by the prebiotic categories contributes to a better understanding of these concepts in the literature, to the stimulation of the processing and consumption of foods rich in fiber and other products with prebiotic properties, and to the development of protocols and guidelines on food sources of prebiotics.

Inclusion of limited amounts of extruded legumes plus cereal mixes in normocaloric or obesogenic diets for rats: effects on intestinal microbiota composition

BACKGROUND

Differences in the composition of the intestinal microbiota and energetic metabolism between lean and obese populations have been described. Legume consumption has been reported to modulate intestinal microbiota composition. However, to the best of our knowledge, no information can be found in the literature on the effects of consumption of diets containing extruded legume plus cereal mixes on the intestinal microbiota composition of rats. Our purpose was to evaluate the effects on lipids profile (see the accompanying paper) and intestinal microbiota composition (current paper) of incorporating this new food ingredient in normocaloric and obesogenic diets.

RESULTS

Intestinal and fecal qPCR-based microbial composition of rats fed the extruded legumes plus cereal mixes differed (P < 0.05) from controls. Obesogenic diets did not affect bacterial counts. However, the inclusion of the extruded mixes reduced (P < 0.05) log₁₀ counts in some bacterial groups and increased (P < 0.05) counts of Lactobacilli, while others remained unaffected. PCoA at the genus level grouped together Lactobacillus reuteri, Akkermansia miciniphila and species from Parabacteroides, Prevotella, Rikenellaceae, and Lactobacillus with extruded legume plus cereal diets. Feeding on extruded legumes plus cereal mixes was associated with increased mRNA expression of the cytokines IL6 and TNF-α and decreased expression of TLR4.

CONCLUSIONS

Our results show that the inclusion in the feed of limited amounts of extruded legumes plus cereal mix, providing a diet that is closer to a normal human one, did modulate the intestinal microbiota composition. Taken together, these results point to the protective, health-promoting properties of extruded legume plus cereal mixes.