Undaria pinnatifida Intake Rapidly Affects the Gut Microbiome Community: A Controlled Feeding Trial

Abstract Objectives The gut microbiome is closely related to health and influenced by dietary intake. However, little is known how seaweed, a food high in fiber, affects the gut microbiome. We investigated the effect of sea mustard (Undaria pinnatifida), a commonly consumed seaweed in East Asia, on the gut microbial community. Methods Forty-two healthy women aged 40–65 years participated as the ocean group (n = 22) or city control (n = 20; CC) for 20 days. The ocean group was housed on an island and participated in a 5-day program of mind-body exercises and controlled-feeding before returning to one's daily routine. Within the ocean group, participants were randomly assigned to control (OC) or to additionally consume sea mustard (OS; 15.4 g dry weight/d; n = 11/group). Sea mustard was provided in various dishes to the OS group during the 5-day program on the island where food intake and activity participation were controlled and monitored. Sea mustard noodles were provided to OS participants to consume during the following two weeks. CC did not receive any intervention. Groups OC and OS collected feces on days 0, 5 (before leaving the island), and 20. CC collected 3 fecal samples within a 20-day period. Fecal samples were sequenced for bacterial 16S rRNA. Analyses were performed by ANOVA, mixed ANOVA, and paired t-test. Results Alpha and β-diversity did not differ between groups at baseline. A time and group interaction was found for α-diversity. Among the top 30 abundant taxa, the only change in the CC group was the decrease in Roseburia by day 20. Lactococcus, Eubacterium_ventrioum_group, Ruminococcaceae_UCG005, and Bifidobacterium increased by day 5 in both OC and OS. The increase in Blautia and decrease in Prevotella observed in OC during the 5-day controlled-feeding period was not found in OS. Specific to OS, Bacteroides increased and Anaerostipes and Catenibacterium decreased by day 5. The abundance of Lachnospiraceae_NK4A136_group was increased throughout the 20-day sea mustard intervention in OS. Conclusions Change in environment can affect the gut microbial community even within 5 days. Sea mustard intake affects α-diversity of the gut microbiome and increases the abundance of Lachnospiraceae_NK4A136_group while preventing the decrease in Prevotella. Funding Sources The Ministry of Oceans and Fisheries, Korea.