A study on the effect of symbiotic fermented milk products on human gastrointestinal health: Double‐blind randomized controlled clinical trial

Several studies have claimed that the consumption of fermented dairy products can improve human gastrointestinal (GI) health. However, the numbers of systematic clinic trials are limited. In this study, a yogurt containing both probiotics and prebiotics was developed and a double‐blind randomized controlled clinical trial was carried out to evaluate the effect of the product on human gastrointestinal health in three different aspects: (1) the effect on functional constipation (FC) and functional diarrhea (FD); (2) the effect on gastrointestinal (GI) tract immune system; and (3) the changes in GI tract microbiota. Participants who suffered FC or FD were randomized into three groups (n = 66 each group): the first group was treated with fermented milk with Lactobacillus plantarum ST‐III (7 mg/kg) and inulin (1.5%), the second group was treated with L. plantarum ST‐III (7 mg/kg) and inulin (1.0%), and the third group (control group) was treated without probiotics and prebiotics. Half of the participants stopped the treatment after 14 days and the rest of the group continued the trial to the full 28 days. The fecal samples of participants were analyzed regarding their short‐chain fatty acids (SCFAs), secretory immunoglobulin A (sIgA), and microbiota. A survey on GI tract health was conducted and the Bristol stool scale was recorded. The results showed that the consumption of the symbiotic yogurt for 14 days and 28 days can both improve the digestive system, with the continual consumption of product containing L. plantarum ST‐III (7 mg/kg) and inulin (1.5%) for 28 days showing the most significance. The consumption of this product may be used as a potential functional food.