Dietary glycemic index, glycemic load, carbohydrate quality index, and low-carbohydrate diet score and their association with sperm DNA damage in unexplained male infertility.

BACKGROUND

Oxidative stress is a key driver of sperm DNA fragmentation (SDF), a molecular defect increasingly identified in men with idiopathic infertility, even when standard semen parameters appear normal. Dietary carbohydrate quality and glycemic properties may modulate oxidative stress, but their relationship with sperm DNA integrity remains underexplored. To examine the association between dietary glycemic index (GI), glycemic load (GL), carbohydrate quality index (CQI), and low-carbohydrate diet score (LCDS) with the odds of elevated sperm DNA fragmentation index (DFI) in men with unexplained infertility.

METHODS

In this case-control study, 300 Iranian men aged 18-50 years (150 with DFI > 30% and 150 with DFI < 20%) were recruited from a fertility clinic. Dietary intake was assessed using a validated 168-item food frequency questionnaire. GI, GL, CQI, and LCDS were calculated. Logistic regression models adjusted for age, BMI, physical activity, energy intake, fat intake, income, smoking, and infertility history were used to assess associations.

RESULTS

Men with higher CQI and LCDS had significantly lower odds of high sperm DNA fragmentation. Specifically, higher tertiles of CQI (Adjusted OR for highest vs. lowest tertile: 0.42; 95% CI: 0.20-0.89; P = 0.023) and LCDS (Adjusted OR: 0.19; 95% CI: 0.10-0.39; P < 0.001) were inversely associated with DFI. No significant associations were observed for GI and GL after multivariable adjustments.

CONCLUSIONS

Higher dietary carbohydrate quality and adherence to a lower carbohydrate dietary pattern showed an inverse association with sperm DNA damage in men with unexplained infertility. These findings suggest a potential link between carbohydrate-related dietary patterns and sperm genomic integrity, but causal relationships cannot be inferred from this observational study.