Omega-3 from fish is widely touted to be good for your heart and brain. Men are often accused of locating those organs in their underpants. But maybe they were right to do so.
A new well-received observational study has found that fish oil supplements was associated with higher semen volume, improved total sperm count and slightly larger testicles.
The study from the University of Southern Denmark is supported by previous research, but none of them are randomised controlled double-blind clinical trials.
This means the results are suggestive but not conclusive.
How did they do it?
Denmark has a conscription system for military service, and all men aged 18 years, except those experiencing severe chronic illness, are required to undergo a physical examination to determine their fitness for military service.
From 2012 to 2017, the researchers attended these examinations, inviting the men to participate in a study of testicular function.
Overall, 1679 young men participated, and were examined at the Department of Growth and Reproduction at Rigshospitalet, Copenhagen, Denmark. They were compensated 500 kr (approximately $100) for their time.
Prior to the day of study participation, all participants completed a questionnaire about their health history, if they smoked, if their mothers had smoked during pregnancy, their diet and alcohol intake, their history of sexually transmitted diseases and other factors, including whether or not they had regularly taken supplements, including fish oil supplements.
On the day of study participation, they delivered a semen sample, had a blood sample drawn, and underwent a physical examination, including measurement of the testicles.
A relatively small number of the volunteers (98 men or 5.8 per cent) reported use of fish oil supplements during the previous three months. Of these, 53 (54.1 per cent) reported intake on 60 or more days.
Findings: Those who took supplements on more than 60 days had bigger and better testicles than those who took them less often.
Will my fertility doctor prescribe fish oil now?
The idea isn’t new.
A 2010 study found that a certain type of omega-3 called docosahexaenoic acid (DHA) was vital for fertility in mice. DHA is one of the most abundant polyunsaturated fatty acids in the human brain.
Experimental mice that lacked the gene responsible for an enzyme important in making DHA were infertile, producing few if any misshaped sperm, all of them bad swimmers.
When DHA was introduced into the diet, fertility was completely restored.
“It was very striking. When we fed the mice DHA, all these abnormalities were prevented,” said Manuel Roqueta-Rivera, a University of Illinois doctoral student at the time, who worked on the study.
A 2012 study of 99 men in the US found an association between a high total fat intake (think: burgers and fries) and lower total sperm count and concentration.
But it also found that men who ate more omega-3 polyunsaturated fats had better formed sperm than men who ate less.
What we can conclude: There’s an association here worth exploring and subjecting to more rigorous testing.
For a variety of experts reactions to the Danish experiment (“well constructed” and “interesting” are commonly invoked) see here.