Dietary patterns and sperm DNA fragmentation in idiopathic infertile men: A case-control study

Sperm DNA fragmentation index (DFI) is a biomarker of male infertility, influenced primarily by oxidative stress. While specific nutrients and antioxidants have been studied, evidence on overall dietary patterns and sperm DNA integrity, particularly in idiopathic infertile men, is limited. This case-control study aimed to investigate the association between empirically derived dietary patterns and sperm DNA fragmentation in men with idiopathic infertility. In this case-control study conducted between May 2024 and March 2025 at a fertility clinic in Tehran, Iran, 310 idiopathic infertile men aged 18-50 years were enrolled. After exclusions, 150 men with high DFI (> 30%) and 150 with low DFI (< 20%) included in the final analysis. Dietary intake was assessed using a validated 168-item semi-quantitative food frequency questionnaire. Principal component analysis identified major dietary patterns. Sperm DNA fragmentation was measured using a standardized sperm chromatin dispersion kit. Multivariable logistic regression models were used to evaluate the association between dietary patterns and high DFI, adjusting for age, BMI, smoking, physical activity, and supplement use. Three major dietary patterns were identified, explaining 26.9% of the total variance in dietary intake: a Plant-Pescatarian pattern (10.2%), a Semi-Western pattern (9.2%), and an Ultra-Processed pattern (7.5%). Higher adherence to the Plant-Pescatarian pattern was significantly associated with lower odds of high DFI in the fully adjusted model (tertile 3 vs. 1: OR = 0.39; 95% CI: 0.15-0.73; P-trend < 0.001). In contrast, the Semi-Western pattern was associated with increased odds of high DFI after adjustment (tertile 3 vs. 1: OR = 3.06; 95% CI: 1.32-7.07; P-trend = 0.008). Similarly, the Ultra-Processed pattern was positively associated with high DFI (tertile 3 vs. 1: OR = 3.77; 95% CI: 2.01-7.07; P-trend < 0.001). Among idiopathic infertile men, adherence to a Plant-Pescatarian dietary pattern was associated with lower odds of elevated sperm DNA fragmentation, whereas greater consumption of Semi-Western and Ultra-Processed dietary patterns was associated with higher DFI risk in a dose-dependent manner. These findings highlight the potential relevance of comprehensive dietary assessment in male infertility, while recognizing that causal inference cannot be established in an observational study.