Effect of Wheat Bran on Fecal Butyrate-Producing Bacteria and Wheat Bran Combined with Barley on Bacteroides Abundance in Japanese Healthy Adults

Abstract

Wheat bran (WB) is rich in insoluble arabinoxylan, while BARLEYmax (BM) is a barley line that is rich in fructan, resistant starch, and β-glucan. In the present study, we investigated which of these two fiber sources would produce more favorable changes in the fecal variables of healthy subjects. Sixty healthy subjects were randomly divided into four groups (n = 15 per group) and fed twice daily for 4 weeks with baked cereal bars containing neither WB nor BM (WB-BM-), WB without BM (WB+BM-), BM without WB (WB-BM+), or WB and BM (WB+BM+). At baseline and after 4 weeks, the fecal microbiota composition and the concentrations of short-chain fatty acids were measured. A significant interactive effect of WB and BM on the abundance of genus Bacteroides was observed at week 4. The abundance of butyrate-producing bacteria and the fecal concentration of n-butyrate were significantly higher in the WB+ groups than in the WB- groups. In conclusion, WB was associated with elevated fecal concentrations of short-chain fatty acids including butyrate owing to an increase in the abundance of butyrate-producing bacteria. Additionally, the combination of WB and BM was associated with an increase in the abundance of genus Bacteroides. Therefore, both WB alone and WB combined with BM favorably influenced the fecal variables of healthy subjects.

Keywords: BARLEYmax; Bacteroides; butyrate producer; fecal butyrate; wheat bran.

Figure 1

Scheme of participant enrollment.

Figure 2

Features of the test foods.

Figure 3

The average relative abundances of detected bacteria genera in stool samples obtained at baseline. No significant differences were observed among the test groups at baseline.

Figure 4

The average relative abundances of detected bacteria genera in stool samples obtained at week 4. A significant interactive effect of WB and BM on the abundances of Bacteroides was observed (p < 0.05). The abundances of Anaerostipes was significantly lower in the WB+ groups than in the WB− groups at week 4 (p < 0.05).

Figure 5

Relationship between the abundance of butyrate producers and the fecal concentration of butyrate at week 4. r = 0.32 (Spearman’s rank correlation coefficient), p < 0.05. ● WB−BM−, ○ WB−BM+, ▲ WB+BM−, ▼ WB+BM+.