Chapel Hill, NC—Past research indicating that antioxidants could have a positive effect on sperm raised hopes in couples dealing with infertility, but a recent conference presentation had some disappointing news.

The U.S. clinical trial of 174 couples found that an antioxidant formulation taken daily by the male partner for a minimum of 3 months had no effect on sperm concentration, motility, or morphology, or the rate of DNA fragmentation, according to the presentation at the European Society of Human Reproduction and Embryology annual meeting in Barcelona, Spain.
For the University of North Carolina at Chapel Hill–led study, all men had been diagnosed with male factor infertility, reflected in subnormal levels of sperm concentration, motility, or morphology, or higher-than-normal rates of DNA fragmentation. With sperm parameters measured at the start of the trial and at 3 months, men allocated to the antioxidant intervention were given a daily supplement (in tablet form) containing 500 mg vitamin C, 2,000 IU vitamin D3, 400 IU vitamin E, 1mg folic acid, 20 mg zinc, 200 mcg selenium, and 1,000 mg L-carnitine. 

Males were treated for a minimum of 3 months, when couples attempted to conceive naturally, or 6 months, with couples receiving clomiphene citrate with intrauterine insemination in months 4 through 6. 

Study authors report that, at 3 months, results showed only a “slight” overall difference in sperm concentration between the two groups, and no significant differences in morphology, motility, or DNA fragmentation measurements. In terms of natural conceptions during the initial 3-month study period, an additional endpoint of the trial, no difference was identified between the intervention and control groups. The pregnancy rate was 10.5% in the antioxidant group and 9.1% in the placebo group, according to the report.

Rates were also comparable at 6 months (after continued antioxidant or placebo for the male partner and three cycles of clomiphene and intrauterine insemination for the female partner), they said.

In explaining the difference in results from previous research, the presentation notes, “Clinical trials suggest that antioxidants have a positive effect on sperm motility, DNA integrity, and pregnancy rates in couples undergoing assisted reproductive technologies; however, there are significant gaps in our knowledge of their impact on male fertility. To date research studies have used: 1) small sample sizes, usually less than 50 subjects, 2) heterogeneous populations and a variety of single antioxidants, 3) changes in semen parameters or DNA integrity as the endpoint, rather than clinical outcomes, and 4) antioxidants in conjunction with in vitro fertilization with intracytoplasmic sperm injection (ICSI) when assessing effectiveness.

“Antioxidants do not appear to improve semen parameters or DNA fragmentation among men with male factor infertility,” the study authors conclude. “While previous data suggest that antioxidants improve pregnancy rates in in vitro fertilization, these data suggest they do not improve in vivo conception.”

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