In summary, some members of the fecal bacteria utilized garlic fructans to grow resulting in a decrease in the pH of the cultures in vitro. Bifidobacteria were stimulated while Clostridia were inhibited by the garlic fructans. Essential oil from garlic has been proven to be an effective antimicrobial substance which may help to improve the gastrointestinal environment by inhibiting pathogens. In this study, it is found that garlic fructans may also improve the microbial environment of the gastrointestinal tract by stimulating beneficial bacteria to grow selectively. The present study is hampered by a few limitations. Compared with some in vivo animal experiments, the diversity of fecal microbiota in this system obviously decreased due to the in vitro environment. However, animal intestinal microflora is not identical to that of human beings.