Collection and analysis of feces
RESTRICTION FRAGMENT LENGTH POLYMORPHISM, HOLIDAY
We asked the participants to collect their feces at a convenient time after a week of recording their bowel movements and intake of probiotic foods. Following the instructions, the participants collected all defecated feces immediately in a special fecal collection cup, stirred them several times with a spoon, and then placed the collection cup in a container, which in turn, was set in a cool bag with the coolant. The participant also evaluated their collected feces using the BSFS. The participants submitted the bag to the researcher as soon as possible (i.e., samples collected in the early morning on weekdays were submitted in the morning; samples collected on campus were submitted promptly; if the samples were collected on a holiday or at night, the participant contacted the researcher, who then picked up the sample at the participant’s home). The submitted fecal samples were stored at − 80 °C until use.We analyzed fecal microbiota by Techno Suruga Laboratory Co., Ltd. (Shizuoka, Japan), using terminal restriction fragment length polymorphism (T-RFLP) targeting the bacterial 16S rDNA. DNA were extracted from the fecal samples according to a previously published protocol [We analyzed fecal BA concentrations by Techno Suruga Laboratory Co., Ltd. (Shizuoka, Japan) using liquid chromatography in combination with hybrid quadrupole time-of-flight mass spectrometry (LC-QTOF-MS). BAs were extracted from fecal samples using a method previously described [