Effects of Shilajit Supplementation on Male Reproductive Parameters in Experimental Animal Models: A Systematic Review and Meta-Analysis

Abstract

Purpose: To systematically review and meta-analyse preclinical animal studies evaluating the effects of Shilajit on male reproductive health, with particular emphasis on testosterone levels, sperm count, sperm motility, and the underlying reproductive mechanisms.

Methods: Eligible animal studies investigating the effects of Shilajit on male reproductive outcomes were systematically reviewed and quantitatively synthesised through meta-analysis. The primary outcomes were serum testosterone, sperm count, and sperm motility, while mechanistic findings were narratively synthesised. A random-effects model was used, and pooled effects were expressed as mean difference (MD) or standardized mean difference (SMD) with 95% confidence intervals (CIs).

Results: Four studies involving 35 animals per group were included in the meta-analysis of serum testosterone, while four studies involving 31 animals per group were included for both sperm count and sperm motility. Shilajit significantly increased serum testosterone levels (MD = 2.69, 95% CI: 1.85–3.53; p < 0.00001; I² = 94%) and sperm count (SMD = 8.14, 95% CI: 2.92–13.37; p = 0.002; I² = 91%). Sperm motility showed a positive but statistically non-significant effect (MD = 25.52, 95% CI: −2.96–53.99; p = 0.08; I² = 99%). The included studies also demonstrated protection against chemically induced reproductive damage through improvements in spermatogenesis, steroidogenesis, and sperm quality. Mechanistic findings associated these effects with activation of antioxidant pathways, including Nrf2/Keap1 and Nrf2/HO-1, increased activities of steroidogenic enzymes such as StAR, 3β-HSD, and 17β-HSD, preservation of Sertoli cell function and blood–testis barrier integrity, improved mitochondrial function, and reduced oxidative stress and apoptosis. Additional narrative evidence supported the potential fertility-enhancing effects of Shilajit.

Conclusions: Preclinical evidence indicates that Shilajit has reproductive-protective effects, significantly improving serum testosterone and sperm count, while its effect on sperm motility remains statistically uncertain. The substantial heterogeneity observed across outcomes highlights the need for standardized experimental methodologies, consistent outcome assessment, dose-response studies, and well-designed clinical trials to establish its efficacy, optimal dosage, and safety in male reproductive disorders.