Effect of apple intake on fecal microbiota and metabolites in humans

The effects of apple intake on the fecal flora, water content, pH, and metabolic activities in eight healthy volunteers and the utilization of apple pectin in vitro were investigated. Although several isolates of Bifidobacterium, Lactobacillus, Enterococcus, and the Bacteroides fragilis group utilized apple pectin, most isolates of Escherichia coli, Collinsela aerofaciense, Eubacterium limosum, and Clostridium perfringens could not. When fecal samples from healthy adults were incubated in liquid broth with apple pectin present or absent, the numbers of Bifidobacterium and Lactobacillus in the former were higher than those in the later. After the intake of apples (2 apples a day for 2 weeks) by eight healthy adult humans, the number of bifidobacteria in feces increased (p < 0.05 on day 7 and p < 0.01 on day 14 of the intake period), and the numbers of Lactobacillus and Streptococcus including Enterococcus tended to increase. However, lecithinase-positive clostridia, including C. perfringens, decreased (p < 0.05), and Enterobacteriaceae and Pseudomonas tended to decrease. Moreover, the concentrations of fecal acetic acid tended to increase on apple intake. The fecal ammonia concentration showed a tendency to reduce and fecal sulfide decreased (p < 0.05) on apple intake. These findings indicate that apple consumption is related to an improved intestinal environment, and apple pectin is one of the effective apple components improving the fecal environment.