Taking fish oil supplements may improve sperm quality in healthy young men, a new analysis suggests.

Researchers studied 1,679 Danish men taking physical examinations for compulsory military service. Their average age was 19, and 98 of them reported taking fish oil supplements during the previous three months.

Compared with those who took none, men who took fish oil supplements for at least 60 days during the previous three months had higher sperm count, a greater proportion of normal sperm cells, higher average semen volume and larger average testicular size. They also had significantly lower follicle-stimulating hormone levels and lower luteinizing hormone levels, both indicators of better testicular function.

There was also a dose-response effect for fish oil: Those who took supplements on more than 60 days had better testicular function that those who took them less often.