Dietary supplements containing zinc and folic acid marketed as a treatment for male infertility do not appear to improve pregnancy rates.
A new study conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) has found that dietary supplements containing zinc and folic acid marketed as a treatment for male infertility do not appear to improve pregnancy rates, sperm counts, or sperm function. The findings were published in the Journal of the American Medical Association.
Most so-called fertility supplements contain zinc and folic acid, according to study authors. Zinc is an essential mineral for sperm formation, and folate, the natural form of folic acid, relies on zinc to help form DNA in the sperm. Previous studies of these nutrients as a treatment for male infertility have produced conflicting results.
In the study, researchers enrolled 2370 couples planning infertility treatments in 4 US cities and their surrounding areas. The men were randomly assigned to receive either a placebo or a daily supplement containing 5 milligrams of folic acid and 30 milligrams of zinc.
Live births occurred at similar rates between the 2 groups, with 404 (34%) occurring in the supplement group and 416 (35%) occurring in the placebo group. The groups also did not differ among measures of sperm health, such as sperm movement, shape, and total count.
The proportion of sperm DNA fragmentation, or broken DNA in the sperm, was higher in the supplement group (29.7%), compared to the placebo group (27.2%). According to the report, previous studies have linked a high rate of sperm DNA fragmentation to infertility.
Additionally, men in the supplement group also had a higher proportion of gastrointestinal symptoms, compared to the placebo group: abdominal discomfort (6% vs. 3%), nausea (4% vs. 2%), and vomiting (3% vs. 1%).
“Our study is  of the first randomized, placebo-controlled trials to assess whether folic acid and zinc supplement help to improve male fertility. [Our] results suggest that these dietary supplements have little to no effect on fertility, and may even cause mild gastrointestinal symptoms,” said Enrique Schisterman, PhD, of the NICHD Division of Intramural Population Health Research, who conducted the trial.
Zinc, Folic Acid Supplement Does Not Improve Male Fertility, NIH Study Suggests [press release]. NIH website. Published January 7, 2020. https://www.nih.gov/news-events/news-releases/zinc-folic-acid-supplement-does-not-improve-male-fertility-nih-study-suggests. Accessed January 7, 2020.