Impact of antioxidant treatment on DNA fragmentation index: a double-blind placebo-controlled randomized trial

Background: Previous reports on effect of antioxidants on sperm DNA integrity were equivocal, and there is a lack of randomized, placebo-controlled studies. Objectives: To evaluate the efficacy of combined antioxidant treatment in subfertile men with normal reproductive hormone levels and high sperm DNA fragmentation index (DFI). Materials and methods: This placebo-controlled, double-blind, randomized study evaluated the effects of combined antioxidant treatment in 77 men from infertile couples, with normal testosterone, LH and FSH levels and DFI ≥25%. All participants were randomly assigned to receive combined antioxidant treatment (vitamins, antioxidants and oligoelements) or placebo for six months. The primary outcome measured was DFI. Secondary outcomes were standard semen parameters. DFI and other semen parameters were, at each time point (pre-treatment, and after three and six months of treatment), compared between the treatment and the placebo group using Mann–Whitney U-test. Results: Antioxidant group had higher sperm concentration after three months of treatment (median: 24.4 × 10⁶/mL vs. 27.2 × 10⁶/mL; P = 0.028) and borderline statistically significant higher concentration after six months of treatment (median: 24.4 × 10⁶/mL vs. 33.3 × 10⁶/mL; P = 0.053) compared to pre-treatment values. The DFI did not change during the 6 months of antioxidant therapy. No statistically significant difference between the antioxidant and placebo group was seen for any of the semen parameters including sperm DFI at any of the three time points. Discussion: The increase in sperm concentration was more pronounced in the antioxidant treated group but not statistically significantly higher than among controls, perhaps due to insufficient statistical power. Previous studies have shown positive effect of antioxidant treatment on DFI and other semen parameters. However, our findings indicate that men with normal reproductive hormone levels may not be the primary target group for such therapy. Conclusion: Six months treatment with antioxidants had no effect on sperm DFI.