The Effect of Dietary Supplements on Male Infertility in Terms of Pregnancy, Live Birth, and Sperm Parameters: A Systematic Review and Meta-Analysis.

BACKGROUND/OBJECTIVES: The aim of this systematic review and meta-analysis was to investigate the effect of dietary supplements on male infertility. METHODS: PubMed, Embase, and CENTRAL were searched from inception to May 2024. Randomized controlled trials with treatment durations of ≥12 weeks investigating the effect of dietary supplements on male infertility compared to placebo were included. Primary outcomes were pregnancy and live birth, while secondary outcomes were sperm concentration, sperm count, total motility, progressive motility, normal morphology, and DNA Fragmentation Index. Risk of bias was assessed using the revised Cochrane risk of bias (RoB2) tool. Data were meta-analyzed using random effects-restricted maximum likelihood models. Certainty of evidence was evaluated using the grading of recommendations, assessment, development and evaluation (GRADE) approach. RESULTS: Of the 3137 articles identified, 50 were included. No effect on pregnancy and live birth was found. Different supplements improved single sperm parameters: Zinc and folic acid and ≥3 substance dietary supplements improved sperm concentration, selenium, carnitine, and coenzyme Q10 improved motility and alpha-lipoic acid improved normal morphology. Vitamin D, vitamin E, and omega-3 fatty acids showed no improvement in sperm parameters. The majority of studies had some concerns or high risk of bias, and certainty of evidence was generally low or very low. CONCLUSIONS: This study found no convincing evidence of an effect of any dietary supplements on male infertility. Larger and more well-conducted randomized controlled trials focusing on specific supplements and considering pregnancy outcomes are needed.