• Impact of Probiotic , Prebiotic and Synbiotic on Gastrointestinal Health : systematic review of clinical trials
  • Amirfaham Rezaee,1 Sina beshkooh,2,* Hedieh Molaei,3
    1. Department of Nutrition, Science and Research Branch, Islamic Azad University, Tehran, Iran
    2. Department of Nutrition, Science and Research Branch, Islamic Azad University, Tehran, Iran
    3. Department of Nutrition, Science and Research Branch, Islamic Azad University, Tehran, Iran


  • Introduction: The gastrointestinal system plays a pivotal role in maintaining overall health, with its balance influenced by the microbiota. Probiotics, prebiotics, and synbiotics have gained attention as potential therapeutic agents for modulating gut health. This systematic review aims to evaluate the clinical efficacy of probiotics, prebiotics, and synbiotics in improving gastrointestinal health, with a particular focus on randomized controlled trials (RCTs).
  • Methods: A comprehensive search was conducted using PubMed, Scopus, Google Scholar, and Medline databases to identify relevant RCTs. Our inclusion criteria encompassed clinical trials that examined the effects of probiotics, prebiotics, or synbiotics on various gastrointestinal outcomes. We identified 27 RCTs, three of which were excluded due to irrelevance. The final analysis included 24 trials, with 17 investigating probiotics, 7 focusing on synbiotics, and 4 evaluating prebiotics.
  • Results: Among the 17 probiotic trials, 15 reported positive effects on gastrointestinal health. These studies demonstrated that probiotics contributed to a reduction in respiratory infections, improved gut dysbiosis, and alleviated symptoms associated with irritable bowel syndrome (IBS). Probiotics were also shown to reduce infection rates in kidney transplant patients and mitigate the adverse effects of clindamycin use. However, two studies reported negative outcomes, emphasizing the variability in probiotic efficacy depending on strain, dosage, and patient population. The seven synbiotic trials yielded six positive results, further highlighting the potential of synbiotics in enhancing gastrointestinal health. Positive effects included a reduction in gastrointestinal infections and improvements in microbial balance. One study presented neutral results, indicating no significant impact on the gastrointestinal outcomes measured. The four prebiotic trials uniformly demonstrated positive effects, particularly in terms of reducing gastrointestinal disorders and promoting the growth of beneficial gut bacteria. These trials underscore the potential of prebiotics as a standalone intervention for improving gut health.
  • Conclusion: In conclusion, this systematic review reveals that the majority of RCTs support the positive effects of probiotics, prebiotics, and synbiotics on the gastrointestinal system. Probiotics, in particular, show promise in addressing various gastrointestinal conditions, while prebiotics and synbiotics contribute to maintaining gut health. Nonetheless, variability in study outcomes suggests that more research is needed to determine the optimal strains, dosages, and target populations for these interventions. Future large-scale trials should aim to standardize treatment protocols and assess long-term benefits for a broader range of patients.
  • Keywords: Synbiotic ; Gastrointestinal health; clinical trials; a systematic review.