Table 2.

Scientific articles in vitro reporting the relation between oat consumption and microbiota modulation.

Authors (Year)	Country	Title	Journal	Food Matrix or Supplement	The Aim	Methodology	Outcomes of Interest
Bai, Zhang, Zhang, Zhang, Huo, Guo (2022) [55]	China	In Vitro Fermentation of Pretreated Oat Bran by Human Fecal Inoculum and Impact on Microbiota	Journal of Functional Foods	Oat bran pretreated	Determine the prebiotic effects of different pretreatments of oat bran.	Oat bran was steamed, microwaved, or dryed with hot air. The samples were exposed to in vitro simulated digestion and added to human fecal inoculum to investigate fermentation metabolites and impacts on microbiota.	Different heat-treatment processes did not impact β-glucan content. Steamed oat bran reduced Escherichia–Shigella and increased Faecalibacterium prausnitzii. Steamed oat bran generated more acetic, propionic, and butyric acid. Steamed oat bran had the greatest effect on gut microbiota diverstiy.
Liang, xie, Evivie, Zhao, Chen, Xu, Liu, Li, Huo (2021) [56]	China	Study on Supplementary Food with Beneficial Effects on the Gut Microbiota of Infants	Food Bioscience	Ready-to-use supplementary food with oat, corn, and millet	Investigate the impact of oat-, corn-, and millet-supplementary foods on gut microbiota and SCFA production.	Oat-, corn-, and millet-supplementary foods and an oligosaccharide control were added to human fecal inoculum from 6 infant donors (age 6–12 months) to investigate fermentation metabolites and impacts on microbiota.	Grain-based supplementary foods had a similar effect on microbiota diversity as oligosaccharides. Total SCFAs were similar across treatments, but the levels of propionate and butyrate produced by oat and corn supplementary foods were greater than oligosaccharides. The supplementary oat food increased the relative abundance of Lactobacillus.
Glei, Zetzmann, Lorkowschi, Dawczynski, and Scholormann (2020) [57]	Germany	Chemo-Preventive Effects of Raw and Roasted Oat Flakes After In Vitro Fermentation With Human Fecal Microbiota	International Journal of Food Sciences and Nutrition	Oat flakes	Analyzed the chemo-preventive effects of raw and roasted oat flakes, evaluating the processing in colon adenoma cells.	The oat flakes were roasted at 140 °C–160 °C for 20 min. The raw and roasted oat flakes were exposed to an in vitro simulated digestion and fermentation with human microbiota. Then, the fermentation supernatants (FS) obtained were characterized, and chemo-preventive effects were analyzed in LT97 colon adenoma cells.	During fermentation, the concentrations of SCFA, especially butyrate, were increased. Oat FS significantly decreased cell growth, which was time- and dose-dependent. The treatment with oat FS increased the caspase 3 activity, the expression of CAT, SOD2 and GSTP, while GPX1 mRNA was decreased. The study indicates chemo-preventive potential through growth inhibition and apoptosis, which is not affected by roasting.
Huang, Yu, Li, Guan, Liu, Song, Liu, and Duan (2020) [51] *	China	Effect of Embryo-Remaining Oat Rice on the Lipid Profile and Intestinal Microbiota in High-Fat-Diet-Fed Rats	Food Research International	Embryo-remaining oat rice (EROR)	Investigate the effects of an extract of EROR on lipid accumulation.	Water and lipid extracts of EROR were incubated with HepG2 cells to evaluate lipid accumulation in vitro.	Oat ethanol extracts significantly reduced lipid concentration, total cholesterol, and triglyceride in HepG2 cells.
Kristek, Wiese, Heuer, Kosik, Schar, Soycan, Alsharif, Kuhnle, Walton, and Spencer (2019) [58]	United Kingdom and Denmark	Oat Bran, But Not Its Isolated Bioactive β-glucans or Polyphenols, Has a Bifidogenic Effect in an In Vitro Fermentation Model of the Gut Microbiota	British Journal of Nutrition	Oat bran, β-glucan extract, oat polyphenols	Evaluate and compare the effects of an oatpolyphenol mix (avenanthramide, hydroxycinnamic acids, and benzoic acid derivatives), β-glucan extract (BG), and oat bran on gut microbiota.	The oat bran was digested in vitro, and the polyphenols were extracted from undigested (raw) and digested (after in vitro digestion) oat bran. Two different doses (1 and 3% (w/v)) of oat bran and matched concentrations of β-glucan extract or polyphenol mix were added to anaerobic fecal batch cultures.	Oat bran increased the abundance of Proteobacteria after 10 h and Bacteroidetes after 24 h, while the concentrations of acetic and propionic acids increased compared to the non-oat control. One percent oat bran increased the SCFA production at 24 h. It increased acetic and propionic acid, and increased the relative abundance of Bifidobacterium; polyphenols and isolated β-glucan did not impact SCFA production. The treatment with β-glucan induced an increase in Bacteroidetes at 24 h. The polyphenol mix induced an increase in the Enterobacteriaceae family after 24 h.
Carlson, Erickson, Hess, Gould and Slavin (2017) [4]	United States	Prebiotic Dietary Fiber and Gut Health: Comparing the In Vitro Fermentations of Beta-Glucan, Inulin, and Xylooligosaccharide	Nutrients	β-glucan and Oatwell (oat bran with 22% β-glucan)	Compare the fermentation effects of prebiotics (inulin, xylooligosaccharides and β-glucan based products) in the production of SCFA.	Five common prebiotic dietary fibers, OatWell, WholeFiber (dried chicory root blend with inulin, pectin, hemi and cellulose), xylooligosaccharide, pure inulin, and pure β-glucan, were incubated in fecal inoculum from healthy adults to measure microbiota, SCFA, and gas production.	Oatwell and β-glucan samples promoted the highest propionate at 24 h of fermentation. Inulin and WholeFiber increased Collinsella and resulted in the highest gas production at 12 h and 24 h of fermentation.

* The study used in vivo and in vitro experiments. Therefore, it is mentioned in Table 1 and this table.