A study found that dietary supplements containing zinc and folic acid do not appear to improve pregnancy rates, sperm counts or sperm function.

Previous studies of these nutrients as a treatment for male infertility have produced conflicting results.

Although zinc and folic acid are often marketed as a treatment for male infertility, it does not seem to make a statistical difference, according to a study conducted by the Eunice Kennedy Shriver National Institute of Child Health and Human Development.

In the current trial, researchers enrolled 2,370 couples planning infertility treatments in four U.S. cities and their surrounding areas.

The men were assigned at random to receive either a placebo or a daily supplement containing 5 milligrams of folic acid and 30 milligrams of zinc.

Live births as well as sperm health, sperm movement, shape and total count did not differ significantly among the two groups.

However, the proportion of sperm DNA fragmentation, broken DNA in the sperm, was higher in the supplement group, compared to the placebo group. Studies have linked a high rate of sperm DNA fragmentation to infertility.

Men in the supplement group also had a higher rate of abdominal discomfort, nausea and vomiting.

“Our study is one of the first randomized, placebo-controlled trials to assess whether folic acid and zinc supplements help to improve male fertility,” said Enrique Schisterman, Ph.D., of the NICHD Division of Intramural Population Health Research, who conducted the trial, along with colleagues. “Our results suggest that these dietary supplements have little to no effect on fertility and may even cause mild gastrointestinal symptoms.”

The study appears in the Journal of the American Medical Association.