A Systematic Review of The Role of Probiotics and Synbiotics on Semen Quality and Sperm Function in Male Infertility

BACKGROUND: With the increasing prevalence of male infertility in recent years, studies on therapeutic interventions leading to improvement in semen quality have increased. There has been increasing interest in recent years in the possible role of probiotics and synbiotics in improving male fertility, especially idiopathic male infertility. This systematic review aimed to assess the effects of probiotics and/or synbiotics on male semen quality and discusses the results, mechanism, and future potential of these interventions in male reproductive health. MATERIALS AND METHODS: A comprehensive systematic search of major databases (PubMed, Google Scholar and Scopus) was conducted using the following search terms ("male infertility" or "semen" or "semen analysis" or "sperm" or "spermatozoa" and "probiotic" or "synbiotic"), without restriction on publication date, and a hand search reference list was also performed between January and March 2025. Only original clinical and animal (rat, mice and dog) studies published in English were included. Observational, in vitro, book, review, editorial, and conference articles were excluded. RESULTS: A total of 296 articles were found, of which 4 randomized clinical studies and 5 animal studies met the inclusion criteria. The results of the included studies suggested that probiotics or symbiotic have significant effects on semen parameters such as motility, morphology, and total sperm count through alleviating oxidative stress, modulating inflammation, regulating reproductive hormones, and restoring gut microbiota balance. CONCLUSION: The available evidence suggests that supplementation with probiotics and synbiotics holds promise for enhancing semen quality. However, the field is limited by small, heterogeneous study populations and short follow-up periods, necessitating larger, well-designed randomized controlled trials (RCTs).