Abstract
The alga Euglena gracilis (E. gracilis) has recently gained attention as a health food, but its effects on human gut microbiota remain unknown. This study aimed to determine the effect of E. gracilis on gut microbiota and defecation due to modulation of microbiota composition in vitro and in vivo. The in vitro model simulating human colonic microbiota revealed that E. gracilis addition stimulated the growth of commensal Faecalibacterium. Further, E. gracilis addition enhanced butyrate production by Faecalibacterium prausnitzii. Paramylon, an insoluble dietary fibre that accumulates in E. gracilis and is the main component of E. gracilis, did not stimulate Faecalibacterium growth in vitro. Daily ingestion of 2 g of E. gracilis for 30 days increased bowel movement frequency as well as stool volume in 28 human participants. Collectively, these findings indicate that E. gracilis components other than paramylon, stimulate the growth of Faecalibacterium to improve digestive health as well as promote defecation by increasing butyrate production.
Highlights
Photosynthetic microalgae are present in both marine and freshwater environments and have attracted attention owing to their potential applications in nutraceuticals[1]
This study aimed to evaluate the effect of E. gracilis consumption on human colonic microbiota in healthy human subjects and validate the findings by analysing effects of adding E. gracilis or paramylon to an in vitro human colonic microbiota model
We investigated the effect of E. gracilis addition (9 g/L) on a single species, Faecalibacterium prausnitzii (F. prausnitzii)
Summary
Photosynthetic microalgae are present in both marine and freshwater environments and have attracted attention owing to their potential applications in nutraceuticals[1]. Information on the composition of colonic microbiota originates mainly from the analysis of faecal samples in human dietary intervention studies. This method is limited by the fact that the production of metabolites, such as short-chain fatty acids (SCFAs), cannot be measured at the actual site (the intestinal tract). An in vitro study method using a model culture system was previously developed in our laboratory to closely reproduce the microbial components in human faecal inoculum[18] This in vitro human colonic microbiota model detected the decreased production of butyrate in ulcerative colitis patients[18]. This study aimed to evaluate the effect of E. gracilis consumption on human colonic microbiota in healthy human subjects and validate the findings by analysing effects of adding E. gracilis or paramylon to an in vitro human colonic microbiota model
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