The Role of Probiotic and Prebiotic Supplementation on Semen Parameters in Idiopathic Male Infertility: A Narrative Review

Abstract

Male factors are the most prevalent cause for infertility in the world.  The "gut-testis axis" theory posits that oxidative stress, systemic inflammation, and dysbiosis of the gut and seminal microbiomes are the primary etiological factors.  This review focused on clarifying the efficacy of probiotic and prebiotic supplements on the semen of men who experience idiopathic infertility. We searched through PubMed (n=82), Scopus (n=71), and the Cochrane Library (n=33) between January 2020 and 2025. The search focused on randomized controlled trials (RCTs) and mechanistic research on Lactobacillus, Bifidobacterium, fructooligosaccharides (FOS), and synbiotics in human subjects or animal models. Total of 22 included studies involved human subjects, while 9 were based on animal models. Synbiotic therapy, such as Lactobacillus strains combined with FOS significantly enhance sperm concentration, progressive motility, and normal morphology compared to a placebo. These medications reduced the levels of CRP and TNF-α, which are signs of systemic inflammation. These therapies also reduce the levels of seminal lipid peroxidation and sperm DNA fragmentation (SDF). Recent findings show that using both synbiotics and antioxidants together is significantly better than using only antioxidants. Probiotic and prebiotic supplementation represents a promising, low-risk adjunctive therapy for idiopathic male infertility by restoring the gut-testis axis, ameliorating oxidative stress, and improving sperm functional integrity.