Functional abdominal pain disorders (FAPD) in children are frequently encountered in clinics; however, adequate treatment options for them are lacking. The prevalence of FAPD is reported 0.2%–23%, and its underlying etiology is poorly understood [1]. The gut microbiota is an essential factor in the development of functional gastrointestinal disorders, and compositional alterations are correlated with many gastrointestinal illnesses [2,3]. This randomized controlled clinical trial evaluated the ability of polymicrobial probiotics (PMP) and mono-strain probiotics (MSP) to relieve childhood functional abdominal pain according to Rome IV Diagnostic Criteria for Irritable Bowel Syndrome. Children were randomly assigned to receive PMP containing a mixture of 6×10⁹ units of Bifidobacterium lactis, Lactobacillus acidophilus, Bifidobacterium bifidum, and Lactobacillus rhamnosus, or MSP containing 8×10⁸ units of Lactobacillus reuteri for 4 weeks. Pain scores in the PMP and MSP groups decreased at 7 weeks after study initiation [4]. However, intergroup differences in pain scores were not significant at any time point. Due to the lack of a placebo group in this study, the reduction of pain intensity with time was insufficient to conclude the effectiveness of probiotics for childhood functional abdominal pain.

The use of probiotics has been an attractive clinical topic for controlling pain related to FAPD or other functional gastrointestinal disorders such as irritable bowel syndrome and functional constipation for several decades because dysbiosis is considered a contributing factor in many functional abdominal disorders [2,3]. Recent studies of the effects of probiotics on childhood functional abdominal pain reported the efficacy of probiotics to be widely heterogeneous, and clinical evidence is still lacking due to the inclusion of diverse probiotic strains [1,4,5]. Among them, L. reuteri might effectively reduce pain intensity in children [6-8]. Dysbiosis seems to be associated with pathophysiological factor in FAPD, and previous randomized controlled trials suggested that L. reuteri may be able to reduce FAPD-related pain in children [6-8]. However, recent recommendations do not encourage the routine use of probiotics to treat childhood functional gastrointestinal disorders due to a lack of evidence [9,10].

The current randomized clinical trial investigated the ability of multi- versus mono-strain probiotics to reduce FAPD-related pain in children. However, it failed to prove that multi-strain L. reuteri probiotics were more effective in relieving pain in children with FAPD than mono-strain probiotics; moreover, data on probiotic mixtures or synbiotics remained limited. Therefore, a well-controlled large-scale clinical study is required to further elucidate this issue.