The differential effect of two cereal foods on gut environment: a randomized, controlled, double-blind, parallel-group study

Abstract

Background and aims: Cereal-based foods such as fruit granola (FG) and corn flakes (CF) form part of a fiber-rich diet. Dietary fiber has a good effect on human health. However, changes in gut microbiota and intestinal immunity have not been investigated. We conducted a randomized, double-blind, placebo-controlled trial to investigate the effects of FG and CF intake on gut microbiota, metabolome, and the immune system.

Methods: Subjects continuously consume CF or FG for 4 weeks. Stool samples, and questionnaires on defecation were collected before, 2 weeks after, and 4 weeks after intake. Gut microbiota was analyzed using 16S rRNA gene amplicon sequencing. Fecal metabolomes were analyzed using GC/MS and CE-TOF/MS. Fecal IgA was analyzed using ELISA.

Results: The defecation frequency after cereal based food intake was improved. The different cereal-based foods had different effects on gut microbiome. The increase in intestinal IgA levels was positively correlated with the relative abundance of Dialister and the Lachnospiraceae ND3007 group in CF and FG group, respectively. SCFAs showed a positive correlation with Prevotella 9 in the FG group.

Conclusion: This study showed that the supplement in dietary fiber contained in CF and FG improves bowel movements. CF and FG each had different effects on gut microbes, metabolites and different relationships between fecal IgA or SCFAs and gut microbiota.

Keywords: corn flakes; defecation; dietary fiber; fruit granola; gut microbiota; short-chain fatty acids.

Figure 1

Schematic overview of the clinical trial in this study. (A) Flow diagram of this trial. (B) Clinical trial diagram and description of time points. Subjects were assigned to either the CF group or the FG group, and they consumed the assigned food for 4 weeks. CF; corn flake, FG; fruit granola.

Figure 2

Intestinal IgA content and defecation frequency in CF and FG groups. Distribution of (A) intestinal IgA content and (B) defecation frequency. The Wilcoxon signed-rank test was performed for comparisons between groups at The Wilcoxon signed-rank test was performed for comparisons between groups at each intake period (0, 2, or 4 weeks). The Wilcoxon signed-rank test was performed for comparisons between groups at each intake period (2 or 4 weeks). CF; corn flake, FG; fruit granola.

Figure 3

Effect of cereal-based food consumption on gut microbiome and metabolome profiles. The (A) weighted UniFrac distance for the gut microbiome and (B) Bray–Curtis distance for quantitative intestinal metabolome profiles among all samples. CF; corn flake, FG; fruit granola.

Figure 4

Effect of cereal-based foods intake on gut microbes and metabolites. (A,B) The volcano plot of the effect on (A) microbes and (B) metabolites of cereal intake. The y-axis represents the logarithm of the Wilcoxon signed-rank test p-value compared with the baseline. lt; 0.05 in y-axis, the point is shown in blue; if q < 0.05 in y-axis, the point is shown in red; otherwise, the point is shown in gray. (C,D) The Venn diagram of (C) microbes and (D) metabolites that show significant increase or decrease. CF; corn flake, FG; fruit granola.

Figure 5

Correlation analysis of gut environment with intestinal IgA. Heatmap of the significantly correlated differential values of IgA content (4w - 0w). Colors show the Spearman coefficients, and stars show Spearman coefficients’ no-correlation test (*, p < 0.05). (A) Correlation differential value before and after intake in IgA content and baseline values of each microbe and metabolite abundance; (B) correlation CF; corn flake, FG; fruit granola.

Figure 6

Correlation analysis of gut environment with SCFAs. Heatmap of the significantly correlated differential values of SCFAs content (4w - 0w). Acetic acid was measured by GC–MS, propionic acid and butyric acid were measured by CE-TOF/MS. Colors show the Spearman coefficients, and stars show Spearman coefficients’ no-correlation test (*, p < 0.05). (A) Acetic acid; (B) Propionic acid; (C) Butyric acid. CF; corn flake, FG; fruit granola.