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

Seiichiro Aoe,Fumiko Nakamura,Suguru Fujiwara

doi:10.3390/nu10121980

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.

Highlights

IntroductionThe mechanisms through which fiber can improve bowel function remain to be fully elucidated
Epidemiological studies have reported that the consumption of whole grain cereals or cereal brans may reduce intestinal transit time, increase the bacterial fermentation of fiber to short-chain fatty acids (SCFAs) with anticarcinogenic properties, and thereby reduce the risk of colorectal cancer [1,2,3].A recent systematic review concluded that high-fiber, wheat-based cereals can improve bowel function with grade A evidence [4].The mechanisms through which fiber can improve bowel function remain to be fully elucidated.One possible mechanism proposed by Sonnenburg et al [5] is that microbiota-accessible carbohydrates found in dietary fiber may substantially influence the microbial ecosystem in the gut
They showed that a diet low in such carbohydrates resulted in a progressive loss of microbiota diversity, which is a type of dysbiosis

Summary

Introduction

The mechanisms through which fiber can improve bowel function remain to be fully elucidated. One possible mechanism proposed by Sonnenburg et al [5] is that microbiota-accessible carbohydrates found in dietary fiber may substantially influence the microbial ecosystem in the gut. They showed that a diet low in such carbohydrates resulted in a progressive loss of microbiota diversity, which is a type of dysbiosis. It is considered that a diet high in fat and low in fermentable dietary fiber shifts the microbiota toward a more dysbiotic pattern associated with an increased risk of intestinal inflammation [7]

Methods

Results

Discussion

Conclusion