A Cochrane review included 48 studies with a total of 4179 men. One group only reported on sperm parameters as their primary outcome.
With oral antioxidants (vitamin E, zinc or combined antioxidants) for men, there was a significant increase in live birth rate (OR 4.21, 95% CI 2.08 to 8.51; P< 0.0001, 4 RCTs, n=277, I²=0%, low quality evidence) compared with placebo or no treatment in follow-up of 6 to 24 months. However, outcome events were few (44 live births from a total of 277 couples in 4 small studies). Antioxidant use was associated with a statistically significant increased pregnancy rate compared to control (OR 3.43, 95% CI 1.92 to 6.11; P < 0.0001, 7 RCTs, n=522 men, I²=0%, low quality evidence). Different antioxidants (Coenzyme Q10, Vitamin E, Zinc, L acetyl carnitine, L carnitine, Magnesium, Vitamin C, pentoxifylline, and in 2 trials combined antioxidants) were compared with placebo or no treatment. No studies reported evidence of harmful side effects of the antioxidant therapy used.
Comment: The quality of evidence is downgraded by risk of bias (unclear sequence generation or allocation concealment) and by imprecise results (few outcome events).