Of weed’s many effects on the body, marijuana’s impact on sperm is perhaps the least obvious — and the most elusive. The research on weed and sperm is contradictory at best.

Some studies hint it could have benefits for sperm production. Others suggest it takes a negative toll. But in September 2019, scientists got a little closer to understanding just what, exactly, marijuana does to sperm.

This is #18 on Inverse’s 25 most WTF science stories of 2019.

When scientists analyzed testicular tissue and sperm samples from a small sample of 15 men, they found endocannabinoids, as well as cannabinoid receptors and the enzymes needed to break those chemicals down. The findings were published in September in Scientific Reports.

Endocannabinoids are neurotransmitters that resemble cannabinoids, the chemicals that occur naturally in cannabis (sometimes called exogenous cannabinoids). The body’s endocannabinoid system extends from the gut to the brain. The results demonstrate that this system extends all the way to men’s sperm-making machinery, too.

Endocannabinoids may be more involved in sperm production than scientists previously thought. Shutterstock

The scientists found traces of an endocannabinoid called 2-arachidonoylglycerol (2-AG) in testicular tissue. They also found genetic transcripts coding for endocannabinoid receptors and evidence that enzymes that break down endocannabinoids were “abundantly present” in germ cells (the cells that become sperm).

Endocannabinoids and sperm production

Study author Niels Skakkebæk said at the time that the results suggest endocannabinoids play a role in sperm production.

“Andrologists like me have for generations been focusing on other hormone aspects but overlooked the possibility that endocannabinoids may participate in the normal sperm and hormone production,” he said.

The presence of those endocannabinoids begs a new question. What happens when you flood that system with more of these chemicals when you smoke weed? Right now, scientists aren’t sure.

It might come down to the amount you actually smoke. A February 2019 paper published in Human Reproduction on “sub-fertile” men showed that marijuana use may be related to higher sperm counts.

That paper noted that 365 men who had smoked weed before had higher sperm counts than the 297 men who hadn’t smoked weed before.

“Low levels of marijuana use could benefit sperm production because of its effect on the endocannabinoid system, which is known to play a role in fertility, but those benefits are lost with higher levels of marijuana consumption,” Feiby Nassan, research fellow at Harvard University, said in a statement.

As 2019 draws to a close, Inverse is counting down the 25 science stories from this year that made us say “WTF.” Some are incredible, some are icky, and some are just plain strange. This has been #18. Read the original article here.