Green tea is a protective factor that can preserve sperm DNA integrity: A retrospective study

Abstract Background: Although sperm DNA fragmentation index (DFI) is an vital biomarker for sperm DNA integrity and male fertility, factors that influence DFI have not been fully elucidated, particularly for occupational exposures and lifestyle factors. Here, we sought to explore the effects of self-reported occupational exposures and lifestyle factors on sperm DNA integrity. Methods: The baseline characteristics, occupational exposures, and lifestyle factors of participants were collected immediately prior to or following semen evaluation through a self-report questionnaire. Participants were separated into three DFI-based groups: DFI<15%, 15%≤ DFI<30%, and 30%≤DFI. Initially, one-way ANOVAs and chi-square tests were employed to investigate the possible factors related to sperm DNA integrity. Then, we performed an ordered logistic regression analysis to detect factors independently associated with sperm DFI. To adjust for relevant confounders, we included factors with a P < 0.25 in univariate analyses as covariates. Results: Among 1,060 subjects who participated in this study, 826 met the icludion cretieria. Univariate analysis showed that age, infertility type, infertility duration, semen parameters (concentration, motility and morphology) and smoking were related to sperm DNA integrity ( P <0.05). At ordered logistic regression analysis, compared with the group that drank green tea 5-7 times/week, the groups that drank green tea <1 time/week (OR=1.52, 95% CI=1.05-2.2, and p=0.027) and 1-4 times/week (OR=1.61, 95% CI=1.02-2.54, and p=0.042) exhibited significantly increased sperm DFI values. Of the traditional semen parameters measured, a positive correlation was noted between sperm DFI and semen volume (OR=1.18, 95% CI=1.07-1.31) and abnormal sperm morphology (OR=1.2, 95% CI=1.11-1.3), whereas it was negatively correlated with sperm motility (OR=0.94, 95% CI=0.93-0.95). Relative to men over 40 years of age, we detected a 65% (95% CI=0.2-0.62) and 58% (95% CI=0.26-0.7) decrease in sperm DFI values in the 20-30 and 30-40 age groups, respectively. Conclusions: These data suggest that green tea consumption is a protective factor associated with the preservation of sperm DNA integrity, which may offer new insights to guide the prevention and treatment of clinical male infertility.