Effects of Undaria pinnatifida (wakame) on the human intestinal environment

Abstract

Background: Undaria pinnatifida (wakame) is an edible seaweed. Wakame is a common food in the Japanese diet which exhibits various biological effects. Wakame is rich in dietary fiber. Despite the long history of its intake, changes in the intestinal environment following the ingestion of wakame are unclear.

Methods: We examined the effect of a 2-week intake of wakame on defecation frequency and the intestinal microbiota of 22 healthy individuals suffering from low defecation frequency. The clinical trial was designed as an open-label study.

Results: Defecation frequency, defined in terms of times per week, days per week, and volume per week significantly increased during the wakame intake period. Furthermore, based on terminal restriction fragment length polymorphism (T-RFLP), the fraction of bifidobacteria as a percentage of all fecal bacteria increased significantly during the wakame intake period. At the phylum, next-generation sequencing (NGS) revealed that the relative abundance of Actinobacteria after wakame intake significantly increased while the abundance of Bacteroidetes decreased. Moreover, species-level analyses revealed that the abundance of Bifidobacterium longum increased significantly after wakame intake. B. longum colony counts on wakame-containing medium were significantly higher than those on medium without wakame.

Conclusion: These observations suggest that wakame intake improves intestinal environment and increases the fecal population of bifidobacteria, indicating that it may have prebiotic properties.

Keywords: Undaria pinnatifida; wakame; bowel movement; intestinal microbiota; fiber; Bifidobacterium