A large-scale US study on male fertility has shown that taking zinc and folic acid supplements do not increase the health of sperm or rate of pregnancy. These findings discredit previous suggestions that regularly taking zinc and folic acid supplements can be an effective, low-cost, non-invasive way to treat male infertility.
Dietary supplements targeting male fertility often contain folic acid and zinc. This is based on limited evidence from previous trials that focused on the effects of zinc and folic acid as both are important for healthy sperm production. The trials relied on small samples and produced conflicting results. However, no large-scale trial has examined the efficacy of folic acid and zinc for improving semen quality or live birth outcomes. This motivated researchers to undertake a large-scale trial.
'There were a few small trials that showed a benefit, but we needed some definitive evidence that this would work,' said lead author and researcher Dr Enrique Schisterman. 'Our study is one of the first randomised, placebo-controlled clinical trials to assess whether folic acid and zinc supplements help to improve male fertility.'
This trial, conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development at University of Utah Health, enrolled 2370 couples from four US cities who were undergoing infertility treatment.
Men were assigned either a daily supplement of 5mg of folic acid and 30mg of zinc, or a placebo. After six months, there was no major difference in live births between the two groups, and there was no major difference in sperm movement or sperm count.
The results also showed that taking the supplements can come with negative side-effects. In the group that took the supplements, there was a slightly higher rate of sperm DNA fragmentation, which can contribute to infertility, and reports of symptoms such as nausea and vomiting.
The study concluded that among a general population of couples seeking infertility treatment, the use of folic acid and zinc supplementation by male partners did not significantly improve semen quality or couples' live birth rates. Hence, the use of folic acid and zinc supplementation by male partners in the treatment of infertility is not supported. James M. Hotaling, co-author of the study says 'The take-home message for men is that, for the first time, there is high-quality data that zinc and folic acid do not improve live birth outcomes or semen function.'