RESUMEN
Few studies have examined the effects of smoking habit, the frequency of alcohol drinking, exercise, and fermented milk consumption on defecatory symptoms and gut microbiota composition, and particularly their interactive effects. We examined the effect of these lifestyle factors on bowel movements and gut microbiota composition in 366 healthy Japanese adults by analysis of covariance. Smoking did not affect defecatory symptoms but was negatively correlated with total bacteria and Enterococcus counts. Drinking frequency was significantly positively correlated with a feeling of incomplete evacuation and counts of the Bacteroides fragilis group and Acidaminococcus groups. Exercise frequency tended to be negatively correlated with the Bristol Stool Form Scale score and was significantly negatively correlated with the counts of Enterobacteriaceae and positively correlated with the Prevotella counts in the faeces. The frequency of fermented milk consumption was not significant but tended to be positively correlated with stool frequency. The frequency of fermented milk consumption was significantly positively correlated with the counts of the Atopobium cluster, Eubacterium cylindroides group, Acidaminococcus group, Clostridium ramosum subgroup, and Lactobacillus in the faeces. The frequency of consumption of probiotic Lactobacillus casei-containing fermented milk was significantly positively correlated with stool frequency. The counts of probiotic Lactobacillus casei in the stool was positively correlated with the counts of Bifidobacterium and total Lactobacillus. These results suggest that smoking, alcohol drinking, exercise, and consumption of fermented milk, particularly containing probiotic L. casei, differently affect bowel movements and gut microbiota composition in healthy Japanese adults.