Couples who are having trouble conceiving a child often go to great lengths to get pregnant. But before they try artificial insemination or in-vitro fertilization (IVF), they first must figure out whether the source of the problem lies with the male or female partner.

For men who learn that their sperm counts and sperm potency are a source of the problem, zinc and folic acid supplements can seem like the best first step. Zinc is essential for sperm development, and folate, the natural form of folic acid, helps form DNA in the sperm. Over-the-counter nutraceuticals containing these ingredients have been promoted as a natural way to improve sperm formation, sperm counts and mobility. Unfortunately, not only do these supplements appear not to work, they may actually damage sperm DNA.

“It's important for men of all ages to eat a healthy diet to maintain fertility, but you don't necessarily need to take something extra to help you achieve better sperm parameters.”

To test the value of zinc and folate as fertility boosters, researchers at the University of Utah recruited nearly 2400 couples getting ready to begin infertility treatments. Men in the couples were randomly assigned to receive either a daily supplement consisting of 5 milligrams of folic acid and 30 milligrams of zinc for six months or a placebo. Once the trial began, women completed questionnaires for up to 18 months to track their whether they became pregnant. Couples in the study came from Salt Lake City, Chicago, Minneapolis and Iowa City, Iowa.

There were no significant differences in live births found between the men who received the supplement and the men given a placebo — 34 and 35 percent respectively. Sperm counts, mobility and shape were also similar between the two groups.

There was one surprising difference: The sperm of men who took the supplements had a higher proportion of broken DNA. DNA fragmentation, as this is known, has been found to contribute to male infertility. Men taking the zinc and folate supplements experienced more abdominal pain, nausea, vomiting and other gastrointestinal symptoms than did men in the placebo group.

Zinc and folic acid supplements can be beneficial, just not for fertility. “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,” said James M. Hotaling, a co-author of the study and a urologist at the University of Utah specializing in male infertility.

The study involved researchers from the Northwestern University Feinberg School of Medicine in Chicago and the University of Iowa Carver College of Medicine, along with those from the University of Utah. “This large, well-controlled, randomized study shows us that nutraceuticals like zinc and folic acid really don't improve the chances of a couple getting pregnant and actually can cause side effects that are not beneficial,” explained C. Matthew Peterson, a reproductive endocrinologist and one of the study's principal investigators. “It's important for men of all ages to eat a healthy diet to maintain fertility, but you don't necessarily need to take something extra to help you achieve better sperm parameters.”

The study is published in JAMA.