Effects of roasted burdock root tea, drink, and the residue on caecal microbiota of mice fed low-dietary fibre diet

Burdock (Arctium lappa) root has been traditionally consumed in Japan since ancient times. Roasted burdock tea (BT) is gaining popularity worldwide as a health drink as it is rich in inulin and chlorogenic acid, and has been reported to have health benefits, including inhibitory and ameliorative effects on constipation and bowel inflammation. However, the underlying mechanism remains unclear. To determine the effects of BT on gut microbiota, diet without cellulose (no fibre: NF), 5% (w/w) whole roasted burdock root powder (WB) diet, 5% (w/v) BT as drinking liquid, or 1.7% (w/w) residue of BT (BR) diet was fed to mice. Microbiota analysis was performed using 16S rRNA (V4) gene amplicon sequencing. The abundance of microbial groups related to obesity and inflammation, such as Allobaculum, was decreased by feeding burdock root preparations, particularly BT (0.6%) compared with NF (25%). Conversely, the abundance of Muribaculaceae, which are gut commensals that correlate with anti-inflammation, immunomodulation, and longevity, in the three burdock groups was 2–3-times higher than that in the NF group. The levels of tumour necrosis factor-α, a pro-inflammatory cytokine, were 2.5-fold decreased in the BT group. In conclusion, BT may affect gut microbiota composition and, thereby, impact the host immune system.