How Lifestyle and Chemical Exposures Affect Male Reproductive Health

Jack Neel: Since the average 18-year-old today has the testosterone of a 60-year-old man in the 1980s, why do young men today have such low testosterone levels?

Dr. Rhonda Patrick: I do think the same things that are causing the sperm to go down are the same things causing testosterone to go down. In that, I think one of the major drivers is, in particular, I think it's the phthalates in these plastics that are being ingested. These chemicals are what are known as endocrine-disrupting chemicals, EDCs. Endocrine-disrupting chemicals, sometimes they're called endocrine-disrupting hormones. They are disrupting hormones, including testosterone, but by a variety of ways. One, they can mimic hormones. Two, they can disrupt the ability of hormones to function. So, hormones have to bind to receptors, and they will block that from happening. And three, they can actually disrupt the actual production of the hormones. So, they can do any or all of these.

And what happens is things like BPA and phthalates are in everything, and we can talk about this, from our water to our food to the air we breathe, everything. And when they make their way into things like semen and other organs, they are disrupting testosterone. There's studies showing, for example, men with the highest levels of phthalates—so, phthalates are something that you'll find in foods that have been packaged in plastic. They're found in just our personal hygiene products, everything from shaving cream, lotions, shampoos, all that stuff, okay? So, men that have the highest level of phthalates have 20% lower testosterone level than men with the lowest level of phthalates.

There's even evidence that a pregnant woman, when she's pregnant and she's exposed to phthalates, the phthalates are getting across the placenta, and they're going into the developing fetus and into the testes, and they're disrupting testosterone production early, early in development, and that's affecting the sexual development of men. The other thing it's doing is it's causing undescended testicles, which is now pretty common in boys. That also affects fertility as well as testosterone production.

So, all this is to say that the phthalates and these plastic chemicals are affecting testosterone starting early in life. And they continue on. And so, men that are being exposed to it—I already cited this study—these men with higher phthalate levels have 20% lower testosterone. And this is a big, wide-ranging age-range study. Young men, old men, across the board. It's affecting everyone, even young men.

The other thing that also people underestimate is sleep. And I know a lot of young people, I mean, they're night owls. They stay up. They want to work. They want to be efficient, productive. Maybe they party, all the above. And so they're not getting the at least 7 hours of quality sleep per night, which is really the minimum of what you need. There was a study showing that young men, these were college students, that got 5 hours of sleep for a week, their testosterone levels dropped by like 15% after 1 week. So, prioritizing sleep, I think people are not getting enough sleep. That's also playing a role.

Refined sugar and ultra-processed foods is another thing that's playing a role in decreasing testosterone levels. So, again, this comes back to, and it's all tangled in with the obesity equation, right? Because when you're eating a lot of ultra-processed foods and a lot of refined sugars, it leads to obesity, right? So, there was a study looking at young men given a really large bolus of sugar, refined, like added sugar, 75 g. It's kind of like a donut and a Coke or Big Mac and a Coke or something like that. A lot of sugar, right? But it tanked their testosterone by like 20% within a couple of hours.

Jack Neel: Really?

Dr. Rhonda Patrick: Yeah.

Jack Neel: Just one dosage of soda pop?

Dr. Rhonda Patrick: Just one dosage. Now, it goes back up, but okay, you're eating sugar throughout the day, all day, every day, right? It's going to start to—

Jack Neel: Adjust your baseline. Yeah.

Dr. Rhonda Patrick: Right. That's going to be your new baseline. It's going to be low. You're going to have lower testosterone levels, right? So, I think that's another—and I'm now rattling off things that are contributing. I think, again, a really big factor here is unfortunately the endocrine-disrupting chemicals, and at the top of the list, phthalates and BPA. But there's the obesity equation also plays a role in testosterone. And then the sleep and the refined sugar are pretty big ones as well. And those are some of the main, I'd say, lifestyle factors that are, I think, playing a role in men having lower testosterone.

Jack Neel: Are there other things destroying men's fertility right now?

Dr. Rhonda Patrick: Yeah, I think there's a lot of things that have been evidence-based to be shown to disrupt testosterone levels and also sperm production and sperm function. I would say, aside from endocrine-disrupting chemicals, of which we've talked about plastic chemicals, there's also another category, which would be the insecticides, pesticides. These are things that are sprayed onto our crops so that we can grow large amounts of food to feed the big people. So, the one that's probably the most associated with lowering sperm number is what's officially called Roundup, glyphosate. So, these organophosphates have been shown in multiple studies to be disrupting hormone production and sperm production as well.

But aside from that, so those are the endocrine-disrupting chemicals, obesity. Obesity is a big factor. Obesity causes damage to sperm in many, many ways. One, it's creating hormones, things like estrogen that are disrupting sperm production, testosterone production, all these feedback loops that happen. Inflammation, oxidative stress, these things also damage sperm DNA. There's a lot of heat that's generated, too, in the scrotum area, and that's also a problem. So, I would say obesity is another major, major player in this story in terms of sperm count and quality going down over the last few decades.

And the other thing would also be, I do mention heat exposure. I've talked a lot about the benefits of deliberate heat exposure, like using a sauna or a hot tub. That is something that does tank sperm number and also their structure and motility. Because in order to make sperm, you have to have a lower temperature in that scrotum area. It has to be lower than your core body temperature. And when that switch gets flipped, you start to basically—you're not making as many sperm. But it is reversible. It goes back to normal once you take away the heat stress after about 2 to 3 months, and studies have shown that as well.

Also, another factor, I think, unfortunately, is exogenous anabolic steroid use, so people that are using exogenous testosterone, anabolic steroids. Men that are using that, that also, as you, I'm sure, know, tanks your production of testosterone in the testes, your natural production, your endogenous production of it. It can be reversible. It's not always. So, unfortunately, some men that are using it, they may not ever have normal sperm production again. Their sperm may not be as good quality. So, while you might hear that it is a reversible phenomena, it may not always be, and I think that's also a part of the story because younger people are using exogenous hormones and steroids. And so, something to consider as well.

So, those are some of the factors that I think are playing a role. A big one really is the endocrine-disrupting chemicals and the obesity. I think those are the two top things that are playing a role.

Jack Neel: That's interesting because, I mean, there's been a rise in—I'm sure you've seen it online—this trend of looksmaxxing. And a big part of it that's being discussed is the usage of TRT and peptides. And I've sat down with a few of these guys on the podcast, and I asked them, "Are you currently infertile?" And they're like, "Yes." And I'm like, "Do you have a problem with that?" And they're just like, "Well, it's temporary." Is that accurate? That it's just temporary until they get off of the dosages they're doing? Or what's the real science there?

Dr. Rhonda Patrick: I think the real science is it could be temporary, but it's like a Russian roulette. Are you going to be the one that it's not? Also, what dose are you doing? How long are you doing it for? Keep that in mind as well. You are taking a chance here with your future fertility if you are going to be doing this looksmaxxing, which, I mean, don't do it. That's ridiculous, honestly. If you're a young guy, first of all, if you're a young guy, your testosterone should be fine. It should be good. And there are things that you can do, and we can talk about that, to kind of help optimize that to the degree that's normal.

Jack Neel: Mhm.

Dr. Rhonda Patrick: There could be a pretty significant trade-off. And if you think just because you read online that it's temporary, again, it's not always. So, are you going to be the person that it's temporary? Are you going to be the one that's not temporary?