Fish oil supplements can boost semen volumes and total sperm counts in men, according to a study published in the Journal of the American Medical Association (JAMA) on 17 January.

Study co-author Tina Kold Jensen, a professor of public health and environmental medicine at the University of Southern Denmark, said fish oil was likely to have 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 key fertilisation events and omega-3 in the sperm membrane increases as the sperm matures," Jensen told news agency UPI.

Fish oil is a source of the omega-3 fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which cannot be manufactured in the body but must be consumed via food.

The Danish study looked at 1,679 men, 98% of whom reported using 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, UPI said.

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.

Supplement users also had 20% lower follicle-stimulating hormones and 16% less luteinising hormones.

As both hormones were considered crucial to sperm development, the results suggested that fish oil could help compensate men with these hormone deficiencies to produce semen in sufficient volumes, the authors said.

The most common reasons for taking fish oil supplements are generally to treat cardiovascular disease, high blood pressure, high triglycerides and high cholesterol.