Oat bran, but not its isolated bioactiveβ-glucans or polyphenols, have a bifidogenic effect in anin vitrofermentation model of the gut microbiota

Abstract

Wholegrain oats are known to modulate the human gut microbiota and have prebiotic properties (increase the growth of some health-promoting bacterial genera within the colon). Research to date mainly attributes these effects to the fibre content; however, oat is also a rich dietary source of polyphenols, which may contribute to the positive modulation of gut microbiota. In vitro anaerobic batch-culture experiments were performed over 24 h to evaluate the impact of two different doses (1 and 3 % (w/v)) of oat bran, matched concentrations of β-glucan extract or polyphenol mix, on the human faecal microbiota composition using 16S RNA gene sequencing and SCFA analysis. Supplementation with oats increased the abundance of Proteobacteria (P <0·01) at 10 h, Bacteroidetes (P <0·05) at 24 h and concentrations of acetic and propionic acid increased at 10 and 24 h compared with the NC. Fermentation of the 1 % (w/v) oat bran resulted in significant increase in SCFA production at 24 h (86 (sd 27) v. 28 (sd 5) mm; P <0·05) and a bifidogenic effect, increasing the relative abundance of Bifidobacterium unassigned at 10 h and Bifidobacterium adolescentis (P <0·05) at 10 and 24 h compared with NC. Considering the β-glucan treatment induced an increase in the phylum Bacteroidetes at 24 h, it explains the Bacteriodetes effects of oats as a food matrix. The polyphenol mix induced an increase in Enterobacteriaceae family at 24 h. In conclusion, in this study, we found that oats increased bifidobacteria, acetic acid and propionic acid, and this is mediated by the synergy of all oat compounds within the complex food matrix, rather than its main bioactive β-glucan or polyphenols. Thus, oats as a whole food led to the greatest impact on the microbiota.

Health benefits of whole grain: effects on dietary carbohydrate quality, the gut microbiome, and consequences of processing

“…Moreover, some of the nonfiber components, sometimes referred to as co‐passengers, also may have biological activity (Fardet, 2010; X. Liu, Le Bourvellec, et al., 2020). For instance, in an elegant study, oat bran (including the co‐passengers) has been shown to be effective in increasing Bifidobacterium populations in the gut, whereas the purified bioactive β‐glucans did not show a bifidogenic effect (Kristek et al., 2019). Nevertheless, some interesting research has been performed on whole grains.…”

Fermented Cereal-based Products: Nutritional Aspects, Possible Impact on Gut Microbiota and Health Implications

“…As whole-grain cereals are also rich sources of dietary fibers, it is controversial whether these effects were solely due to the phenolic compounds alone [109]. In an in vitro fermentation simulating the digestion from mouth to small intestine, Kristek et al [110] studied the impact of 1% and 3% intake of oat bran, β-glucan extract, and polyphenol extracts separately. The results showed that the polyphenol mix increased the Enterobacteriaceae family within 24 h, but the most significant impact (increment of bifidobacteria, enhanced production of propionic and acetic acid) on the gut microbiota was achieved with the digestion of oats and not by a single group of compounds; this implies a synergistic effect of the dietary fibers and polyphenols on gut microbiota and also points to the lack of energy for microbial growth in the case of using single compounds as substrates.…”

The Cholesterol-Lowering Effect of Oats and Oat Beta Glucan: Modes of Action and Potential Role of Bile Acids and the Microbiome

“…A recent study using an in vitro batch culture system demonstrated that oat β-glucan induced proliferation of Bacteroidetes but was not Bifidogenic. In contrast growth of Bifidobacteria was stimulated by oat-derived polyphenols (82). In another study oat flakes promoted growth of the Bacteroides/Prevotella group or Bifidobacterium group in a fecal slurry with effects related to the size of the oat flakes (31).…”