Does Marijuana Affect Sperm Quality and Male Fertility? (Episode 551)

Full Transcript: Episode 551

Lisa Hendrickson-Jack:

This is the Fertility Friday Podcast, episode number 551. Today I’m sharing a brand new episode in my FAMM Research Series. I was actually having a random conversation with my husband, and he asked a really interesting question. We’re of West Indian background, and somehow in the course of regular conversation, we were talking about marijuana and the negative impact it has on sperm quality. He asked: there’s this whole idea that Rastas — so that’s a whole thing — but Caribbean men who follow that religious belief tend to smoke more marijuana. He said there’s this belief that they just have such high fertility. What’s the story on that?

I mentioned there’s a study I cited in Real Food for Fertility that specifically looked at marijuana use among Jamaican men. He said, that’s so interesting. And I said, you know what? I should probably do a FAMM Research Series episode on that, because I think it would be really interesting information. So that’s exactly what we’re going to do. I think by the end of it, you might have more clarification on how marijuana impacts fertility, and for those of you familiar with that background story about Rastamen and high fertility, it might shed some light on why marijuana use affects some men differently than others.

So the name of the study is “Marijuana Use and Its Influence on Sperm Morphology and Motility: Identified Risk for Fertility Among Jamaican Men.” If you want more details, head over to the show notes at fertilityfriday.com/551. This is the very first study looking specifically at the impact of smoking marijuana on the sperm quality of Caribbean men in particular — which is one of the reasons why we’re talking about it.

Just to put it all into perspective: I’ve talked about sperm quality a lot over the years, and I wrote extensively about it in Real Food for Fertility. Chapter 9 — the sperm quality chapter — is a dense, jam-packed chapter that condenses a ton of highly scientific information into a very readable format. If this episode piques your interest, that chapter will give you a much deeper dive.

The background in general is that many of us have heard the statistics — there’s been a worldwide decline in sperm quality over the past 70 years. I highlighted this in The Fifth Vital Sign as well. If you pull studies from the 1940s and look at sperm quality, the average man then had anywhere from 100 to 115 million sperm per milliliter. That was just the average. Today, the average is falling closer to 50 million sperm per milliliter. That tells us something is going on. The reasons are multifactorial — diet quality, health status, metabolic issues, use of recreational drugs, alcohol, and cigarettes all potentially play a role. That’s part of what led the researchers to focus on this topic.

They also reported that in Jamaica, up to 30% of the population has used marijuana, and the most recent National Health and Lifestyle Survey revealed that 17% of Jamaicans are current users, with the majority being young males in reproductive age. So they wanted to know: if this much of the population is using marijuana, how is it actually affecting fertility?

The study enrolled couples who were already seeking fertility assistance. There were 229 participants who provided their data. Not the biggest sample size, but you can still gain meaningful insights from smaller studies. The researchers assessed each man’s marijuana use history — defining “ever use” as use within the past five years. They looked at recent use, frequency, and quantity. They also controlled for other lifestyle factors like cigarette smoking, so that they could isolate the effect of marijuana specifically.

They used the 2010 WHO World Health Organization guidelines to define what is normal. Normal motility: 40% or greater of sperm being motile. Normal concentration: 20 million sperm per milliliter or higher. Normal morphology: 4% or greater normal forms. Anything below those numbers is considered abnormal. This is the same bar used in clinical labs — so these findings are directly applicable to real-world semen analysis.

In terms of the study participants, 70% were age 40 or younger, with ages ranging from 23 to 72. About 47% reported using marijuana at all, and 21% reported using it recently.

Now for the most interesting results. The factors most highly correlated with abnormal morphology were not necessarily frequency or recency of use — it was specifically the quantity. Users of large quantities of marijuana were at a significantly higher risk of having abnormal sperm motility: anywhere from two and a half to four times more likely. And moderate quantity users were over three times more likely to be diagnosed with abnormal morphology. So it wasn’t necessarily the regularity — there were many men who reported themselves as regular users but weren’t necessarily heavy smokers — and there wasn’t as strong an association with regularity in terms of motility and morphology specifically. But the quantity of use — the heavier and moderate users — was associated with a meaningful negative impact.

Another interesting finding was that recent users were 40% more likely to have abnormal sperm motility. The researchers speculated about why: we all have an endocannabinoid system that is receptive to the cannabinoids in marijuana, and sperm have been reported to have these receptors as well. That was one of their possible explanations for why recent use specifically was related to an increased risk of abnormal motility.

So what does all of this mean? Going back to the conversation with my husband — men who are regular casual smokers but don’t smoke a lot, maybe a few times a week at a small amount, didn’t show as strong a negative risk associated with regularity or frequency alone. But when it came to quantity, there was an association. And I think this gives some explanation into that backstory about Rastamen having high fertility. It could be that the frequency plays a role.

There was another interesting finding: the men who had other negative factors for fertility — those who had been trying to conceive for a long time or had other risk factors — seemed to be more heavily impacted by marijuana use in particular. In other words, men who were already at risk or already susceptible to fertility challenges — the marijuana use just made it worse. It didn’t help. This could speak to a lesser degree of resiliency or a greater susceptibility in that group.

In practical terms: if you’re trying to conceive and marijuana is a factor, be cautious. If you’ve been trying for a while with limited success and marijuana is in the picture, the research suggests the best thing would be to reduce or eliminate use if possible. From the practitioner perspective, this is something to be asking about — it shouldn’t be slipping through the cracks.

What about edibles? This study didn’t look at edibles specifically. In Real Food for Fertility, we reviewed different studies that did look at the effect of THC specifically — not limiting it to smoking. There is some suggestion that the active ingredient THC plays a role in sperm quality even when ingested rather than smoked. There isn’t as much research specifically on edibles yet, but if you’re already in a reproductive category where you’re struggling, there’s enough general information to say that edibles wouldn’t help. Marijuana is not a health food or supplement that is going to benefit sperm quality. That’s simply not something we see in the research.

The researchers also mentioned the trend of increasing legalization. In Jamaica, recent legislative changes had loosened restrictions slightly. And certainly in Canada — where I live — cannabis is now legal, widely available, and socially open in a way it simply wasn’t before. Pot shops are on every corner, people smoke openly, and you smell it walking around. The researchers’ concern was: now that it’s more visible and socially acceptable, use is going to increase. And given that sperm quality was already declining before these legislative changes, I do have concerns. Do young people really know the negative impact that marijuana could have on their fertility? I genuinely have to wonder whether the younger generation has been given this information — because one of the things we talk about on this show consistently is that we’re not taught much about our reproductive health at all. People don’t learn about menstrual cycles, fertility awareness, how to time intercourse, let alone the impact of recreational drug use on fertility.

I’ll close on a note of hope. I have seen in working with clients over the years that it does make a difference when people are able to make these changes. When a client who’s a heavier user of marijuana finds a way to significantly reduce or eliminate use over time — not instantly, but consistently over the course of four to six months — plus adding specific nutrients and antioxidants that reduce sperm DNA damage, I have seen really significant improvements. And one of the great things about sperm quality is that it is measurable. You can do the test, make the changes, and see what’s improved within four to six months. That can be a really powerful motivation, especially when you’ve been trying for a while and need some hope. Marijuana use is typically something we can have some control over — and that’s where I like to focus.

If you’ve been enjoying the FAMM Research Series, you can find a full list at fertilityfriday.com/research. Until next time, be well and happy charting.