Jan. 17 (UPI) -- Men struggling with infertility may have an alternative to invasive treatments in the form of fish oil supplements, a new study suggests.

In an article published Friday in the Journal of the American Medical Association, researchers from Denmark found that men who used the nutritional supplement -- known for its key ingredient, omega-3 fatty acid -- had higher semen volumes and total sperm counts, as well as increased levels of free testosterone, compared to men who didn't use as frequently or at all.


According to study co-author Tina Kold Jensen, a professor of public health and environmental medicine at the University of Southern Denmark, fish oil likely has these effects because "a rich fatty acid content" in the sperm cell membrane "is critical for proper sperm function."

"The sperm cell membrane plays a critical role in the key fertilization events, and omega-3 in the sperm membrane increases as the sperm matures," Jensen told UPI. "It cannot be synthesized endogenously in humans and needs to come from diet."

This is not the first study to link fish oil with male fertility, but it is perhaps the most comprehensive to date. Michael L. Eisenberg, director of men's health and male reproductive medicine at Stanford University School of Medicine, noted that research has historically been inconclusive as to how or why the supplement boosts sperm counts, although it has been suggested that its anti-inflammatory properties may play a role.

"Prior studies have suggested associations between fish oil intake and semen quality," Eisenberg, who was not involved in the Denmark research, told UPI. "However, the data is limited."

Because of that, he added, fish oil supplementation is not "routinely recommended" as a treatment for male infertility, at least in the United States.

The analysis in Denmark included 1,679 adult males, 98 of whom reported use of fish oil supplements during the prior three-month period and 53 of whom said they used the supplement for 60 or more days over the course of that period.

Compared to men with no supplement intake, those who took a fish oil supplement for less than 60 days had up to one-third greater semen volumes, while those who used it for more than 60 days had semen volumes nearly two-thirds higher. Fish oil users also had larger testicular size, and slightly -- up to 1 percent -- higher levels of free testosterone.

Those who took the supplement also had significantly lower levels of follicle-stimulating hormone and luteinizing hormone -- 20 percent and 16 percent -- than the men who didn't.

As both hormones are considered crucial to sperm development, this suggests that fish oil may be able to help men with deficiencies compensate for them and still produce semen in sufficient supplies, the authors said.