EPA increases testosterone levels
The testes of young men who take fish oil supplements function better than those of men who don't take supplements, we reported a few days ago. Via Twitter, thanks to a well informed follower, we got hold of an animal study that shines more light on the association between fish oil and testicular functioning. That study was published in Biochemistry and Biophysics Reports in 2016, and it argues that the fish fatty acid EPA makes the testes respond better to LH.
The researchers, affiliated with Kinda University, gave mice food enriched with fish oil for 10 weeks. The researchers used a fish oil produced by the Japanese Nippon Suisan Kaisha, which was extracted from sardines. The fish oil consisted of 31 percent EPA and 16 percent DHA.

If the mice had been adult humans, they would have been fed 4-6 grams of fish oil daily. The researchers could probably also have used lower doses, but the experiment might have been taken more time.
A control group was given food without fish oil.
The supplementation increased the concentration of testosterone in the testes and the blood of the mice.


Based on their own research and other previously published animal studies [J Nutr. 1990 Jun;120(6):610-8.] the Japanese suspect that omega-3 fatty acids - especially EPA - make the testosterone-producing cells in the testes more sensitive to LH receptors by altering the cells' membrane. LH is a hormone that is released by the pituitary gland in the brain and stimulates the testes to produce more testosterone.The Japanese also did an animal study in which they pumped lab mice a hefty amount of fish oil into their stomachs every day for a week. This worked less well. Apparently the body needs time to build EPA into cellular structures.
"These data indicate that Leydig cells have an unidentified system to incorporate EPA selectively into the plasma membrane, and EPA may be crucial in testosterone metabolism," the researchers write. "The modulation of serum testosterone by a functional food (or similar factors) may be effective in preventing some of the diseases associated with low serum testosterone levels."

The study was funded by the Japanese government, not the supplement industry or any fishing industry organization.

Biochem Biophys Rep. 2016 Jun 30;7:259-65.