A large clinical trial conducted in the U.S. has shown that daily antioxidant supplementation among men with infertility does not make a difference to the quality of their sperm.
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Although previous studies have suggested that taking antioxidants improves abnormal sperm parameters, the current study showed daily antioxidant supplementation among infertile males over three months did not improve sperm concentration, motility or morphology, nor the rate of DNA fragmentation.
The authors say that much of the research where antioxidants have been associated with improved sperm quality has been limited by small study groups, patient heterogeneity, variation in the antioxidants tested, and non-clinical endpoints.
The current trial, which is being presented today at the 34th Annual Meeting of the European Society of Human Reproduction and Embryology was designed to address these limitations and provide a stronger evidence base.
According to Professor Anne Steiner (University of North Carolina) who is presenting the findings, this randomised controlled trial is one of the largest of its kind and has a "well characterised" study population involving 174 couples across eight fertility centers in America.
All male partners included in the trial had been diagnosed with male factor infertility and had abnormal sperm parameters including sub-normal sperm levels, motility, or morphology, or increased DNA fragmentation.
These parameters were measured at the beginning of the study and at three months, after one group of men had received daily supplementation with vitamins C, D3 and E, zinc, selenium, folic acid and L-carnitine and another group had received a placebo.
The researchers observed only a slight overall difference in sperm concentration between the two groups and no significant differences in measurements of sperm morphology, motility or DNA fragmentation.
A further clinical endpoint of the trial was natural conception during the three-month study period. However, no significant difference between the two groups was seen for this endpoint either.
Based on these findings, Steiner and team conclude that "the results do not support the empiric use of antioxidant therapy for male factor infertility in couples trying to conceive naturally."