L-Methionine Improves Sperm DNA Integrity and Functional Semen Quality in Infertile Men: A Randomized Controlled Study
Marwan Abdulaziz Ibrahim *
Department of Urology, Teaching Al-Diwaniyah Hospital, Al- Diwaniyah, Iraq.
*Author to whom correspondence should be addressed.
Abstract
Background: Sperm DNA fragmentation index is considered an important marker of male reproductive potential. Increased DNA fragmentation is associated with impaired semen quality and poor reproductive outcomes. However, effective targeted therapies to improve sperm DNA integrity remain limited.
Aims: To evaluate the effect of L-methionine supplementation on sperm DNA fragmentation and conventional semen parameters in infertile men with elevated sperm DNA fragmentation.
Materials and Methods: This prospective randomized double-blind placebo-controlled trial was conducted between May 2024 and May 2025 at the infertility clinic of Diwaniyah teaching hospital in Iraq. A total of 40 infertile men with elevated sperm DNA fragmentation were randomly assigned in a 1:1 ratio to receive either oral L-methionine (500 milligrams twice daily) or matching placebo for 12 weeks (20 participants in each group). In addition, 20 fertile men were included as a reference control group. Conventional semen parameters and sperm DNA fragmentation were assessed before and after intervention using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling assay.
Results: L-methionine supplementation resulted in significant improvement in progressive motility, sperm morphology, and sperm viability, along with a significant reduction in sperm DNA fragmentation compared with placebo. No significant change was observed in sperm concentration. Between-group comparisons showed greater improvement in semen parameters and DNA integrity in the L-methionine group. Correlation analysis showed an inverse relationship between reduction in DNA fragmentation and improvement in progressive motility.
Conclusions: L-methionine supplementation was associated with improvement in sperm DNA integrity and semen quality in infertile men with elevated DNA fragmentation. These findings suggest a potential role for L-methionine in the management of male infertility associated with increased sperm DNA damage.
Keywords: Male infertility, sperm DNA fragmentation index, L-methionine, sperm motility, semen quality, DNA integrity