How to Safeguard Your Hormone Health & Fertility | Dr. Shanna Swan

1. 0:00 – 2:58

   Dr. Shanna Swan

   1. AHAndrew Huberman0:00

      Welcome to the Huberman Lab podcast, where we discuss science and science-based tools for everyday life. I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. My guest today is Dr. Shanna Swan. Dr. Shanna Swan is a professor of environmental medicine and public health at the Mount Sinai School of Medicine. She is a world expert in how exposure to various toxins and compounds in the food and environment impact our reproductive health. She focuses on how these compounds in our air, in our food supply, in our water supply, in cosmetics, even in household items, impact the developing fetus, children, and adults at the level of their reproductive biology, so things like testosterone and estrogen and the pathways within the brain and body that are impacted by testosterone and estrogen, but also how all those things in our environment and that we put into our body impact our health on a daily basis and our long-term health. So during today's discussion, you will learn why fertility rates are indeed dramatically dropping from year to year and have been for quite some time now. You'll also learn why testosterone levels are dropping, why sperm counts are dropping, why things like polycystic ovarian syndrome are increasing in women, and what we can do about it. In fact, during much of today's discussion, Dr. Swan emphasizes the things that you can do every single day and that, in fact, turn out to be very simple. They involve certain things to do and certain things to avoid in order to limit your exposure to these environmental toxins and their impact. So by the end of today's episode, you will be highly informed by the world expert on endocrine disruptors and environmental toxins, and you will also be highly informed in terms of how you can have agency, how you can take control of your health in relation to these various compounds. Before we begin, I'd like to emphasize that this podcast is separate from my teaching and research roles at Stanford. It is, however, part of my desire and effort to bring zero-cost-to-consumer information about science and science-related tools to the general public. In keeping with that theme, I'd like to thank the sponsors of today's podcast. Our first sponsor is LMNT. LMNT is an electrolyte drink that has everything you need and nothing you don't. That means the electrolytes, sodium, magnesium, and potassium, in the correct ratios, but no sugar. We should all know that proper hydration is critical for optimal brain and body function. In fact, even a slight degree of dehydration can diminish your cognitive and physical performance to a considerable degree. It's also important that you're not just hydrated, but that you get adequate amounts of electrolytes in the right ratios. Drinking a packet of LMNT dissolved in water makes it very easy to ensure that you're getting adequate amounts of hydration and electrolytes. To make sure that I'm getting proper amounts of both, I dissolve one packet of LMNT in about 16 to 32 ounces of water when I wake up in the morning, and I drink that basically first

2. 2:58 – 6:49

   Sponsors: LMNT, ROKA & BetterHelp

   1. AHAndrew Huberman2:58

      thing in the morning. I'll also drink a packet of LMNT dissolved in water during any kind of physical exercise that I'm doing, especially on hot days when I'm sweating a lot and losing water and electrolytes. There are a bunch of different great-tasting flavors of LMNT. And now that we're entering the winter months, at least here in the Northern Hemisphere, LMNT has their chocolate medley flavors back in stock. I really like these chocolate flavors, especially the chocolate mint when mixed into hot water. And of course, despite being a bit colder outside, hydration is still critically important. In fact, a lot of people don't realize this, but even when it's cold out, it's easy to get dehydrated, and that's because the air is dry, and so even though you don't notice the accumulation of sweat on your skin, you can still be losing a lot of water and electrolytes. If you'd like to try LMNT, you can go to drinklmnt.com/huberman to claim an LMNT sample pack with the purchase of any LMNT drink mix. Again, that's drink LMNT, spelled L-M-N-T, so it's drinklmnt.com/huberman to claim a free sample pack. Today's episode is also brought to us by ROKA. ROKA makes eyeglasses and sunglasses that are of the absolute highest quality. I've been wearing ROKA readers and sunglasses for years now, and I love them. They're lightweight, they have superb optics, and they have lots of frames to choose from. I'm excited to share that ROKA and I have teamed up to create a new style of red lens glasses. These red lens glasses are meant to be worn in the evening after the sun goes down. They filter out short wavelength light that comes from screens and from LED lights, the sorts of LED lights that are most commonly used as overhead and, frankly, lamp lighting nowadays. I want to emphasize, ROKA red lens glasses are not traditional blue blockers. They're not designed to be worn during the day and to filter out blue light from screen light. They're designed to prevent the full range of wavelengths that suppress melatonin secretion at night and that can alter your sleep. So by wearing ROKA red lens glasses, they help you calm down, and they improve your transition to sleep. Most nights I stay up until about 10:00 PM or even midnight, and I wake up between 5:00 and 7:00 AM, depending on when I went to sleep. Now I put my ROKA red lens glasses on as soon as it gets dark outside, and I've noticed a much easier transition to sleep, which makes sense based on everything we know about how filtering out short wavelengths of light can allow your brain to function correctly. ROKA red lens glasses also look cool, frankly. You can wear them out to dinner or to concerts or out with friends. So it turns out it is indeed possible to support your biology, to be scientific about it, and to remain social after all. If you'd like to try ROKA, go to roka.com, that's R-O-K-A dot-com, and enter the code Huberman to save 20% off your first order. Again, that's R-O-K-A dot-com, and enter the code Huberman at checkout. Today's episode is also brought to us by BetterHelp. BetterHelp offers professional therapy with a licensed therapist carried out entirely online. Now, I've been doing weekly therapy for well over 30 years. In fact, I consider doing regular therapy just as important as getting regular exercise, including cardiovascular exercise and resistance training exercise, which of course I also do every week. Now, there are essentially three things that great therapy provides. First, it provides a good rapport with somebody that you can really trust and talk to about any and all issues that concern you. Second of all, great therapy provides support in the form of emotional support, but also directed guidance, the dos and the not-to-dos. And third, expert therapy can help you arrive at useful insights that you would not have arrived at otherwise. With BetterHelp, they make it very easy to find an expert therapist with whom you can really resonate with and provide you with these three benefits that I described. Also, because BetterHelp is carried out entirely online, it's very time-efficient and easy to fit into a busy schedule with no commuting to a therapist's office or sitting in a waiting room or looking for a parking spot. So if you'd like to try BetterHelp, go to betterhelp.com/huberman to get 10% off your first month. Again, that's betterhelp.com/huberman. And now for my discussion with Dr. Shanna Swan.Dr.

3. 6:49 – 13:30

   Environmental Chemicals, Fertility, Hormones, Phthalates

   1. AHAndrew Huberman6:49

      Shanna Swan, welcome.

   2. SSDr. Shanna Swan6:51

      Dr. Andrew Huberman, thank you (laughs) .

   3. AHAndrew Huberman6:55

      I'm super excited for today's conversation. I've followed your work for a number of years. I've seen some of your appearances on other podcasts, and I got to see you speak while we were both in Copenhagen. I was in the audience, you didn't know I was there, but-

   4. SSDr. Shanna Swan7:11

      (laughs)

   5. AHAndrew Huberman7:11

      ... incredible stuff that you've been doing at, as a researcher, as a public educator, as a writer. Let's kick off by just asking the basic question: Are there things in our environment, including our food, that are diminishing our reproductive and overall health? And if so, which are the ones that you think about, and perhaps you could just mention a few of the more salient, um, maybe even shocking, but salient results that you've observed over the years. Like what was-

   6. SSDr. Shanna Swan7:46

      (laughs)

   7. AHAndrew Huberman7:46

      ... what was the, the kind of like, whoa result or results that have really, um, steered your attention in the last couple of decades? And I'll just say what we were talking about before we were on the microphone, which is that you are a skeptic. You are not somebody who walks out into the world and looks for things that could be messing up our s- our biology, messing up our health. And yet, you found some. So if you could just share with us, uh, what you've observed and what you find really compelling and important for people to know about, we can dive in there.

   8. SSDr. Shanna Swan8:16

      That was a lot of questions. I could probably-

   9. AHAndrew Huberman8:18

      Yeah.

   10. SSDr. Shanna Swan8:18

       ... talk for a long time (laughs) .

   11. AHAndrew Huberman8:20

       Feel free. I won't speak until you're done.

   12. SSDr. Shanna Swan8:22

       But, but, no, but I wanna break it up. Let's break it up. So I think the first question about was, are there forces, chemicals, agents in the environment that can affect our reproductive health, yes? Okay. So my answer to that is yes. I think there's no question about that. The question comes down to when, and in whom, and, uh, at what dose and so on and so forth. But whether there are, let's just say broadly, things? Yes, of course. Um, the category that I focus on are man-made, primarily man-made chemicals, although I do also include the influence of other factors, factors of choice, ch- fac- for example, sleep, exercise, that kind of thing. We can talk about that. But let's just focus here on the, on the chemicals, 'cause I think that's what led me to do a lot of my research and to write the book that I wrote. And, um, so my, um, thesis is that chemicals in the environment, that's a very broad class, so we'll have to say some chemicals in the environment, at the right time, to the right organism, affect fertility, okay? So, and let me just say, fertility is one area that I'm focused on, but actually this class of chemicals that I'm primarily interested in are those that affect the body's hormones. So those are known as hormone disrupting chemicals or endocrine disrupting chemicals. Um, hormone altering chemicals, whatever, you know, there's a lot of names. But that helps you focus on where to look for the effects. 'Cause if it's hormone altering, you can now have something to really ask. Okay, here is a chemical, does it affect a hormone? Which hormone? When? How? And then you start to, that's almost an, laying out an experiment right there, right? So, so focusing in on hormone disrupting chemicals I think is useful.

   13. AHAndrew Huberman10:33

       Absolutely.

   14. SSDr. Shanna Swan10:34

       Yeah.

   15. AHAndrew Huberman10:34

       Yeah, and I think much of what we'll talk about today probably centers on the estrogen and testosterone pathways as they relate to masculinization or feminization-

   16. SSDr. Shanna Swan10:46

       Right.

   17. AHAndrew Huberman10:46

       ... of the brain and body.

   18. SSDr. Shanna Swan10:47

       Right.

   19. AHAndrew Huberman10:48

       And sperm and egg-

   20. SSDr. Shanna Swan10:50

       Right.

   21. AHAndrew Huberman10:50

       ... quality.

   22. SSDr. Shanna Swan10:51

       So I'm a reproductive epidemiologist. I got there in an indirect path. I think probably my work on, um, oral contraceptives led me there most directly. And oral contraceptives are endocrine disrupting chemicals. Uh- (laughs)

   23. AHAndrew Huberman11:10

       It's what they're designed to do.

   24. SSDr. Shanna Swan11:11

       (laughs) Right? That's what they're designed to do, change your body's hormones, your reproductive hormones. So it's interesting, you know, way back when, when I worked on the study at Kaiser on oral contraceptives, which was the largest study of its kind in the world actually, trying to figure out were there adverse effects of oral contraceptives? If so, you know, for whom and when and how much and so on. And so it was a very great study and, um, coming forward in time, um, I, you know, I studied environmental chemicals, not so much pharmaceuticals, um, for quite a while in, when I was at the California Department of Health Services. And, and then I had an a-ha moment. Um, I was flying to Japan with my friend John Brach who's a chemist at CDC, wonderful chemist. And, you know, we had a long flight, so we were talking about this and this and he says, "Shanna, you should look at phthalates." And I'm going, "Why should I look at phthalates?" I'd never heard of phthalates, right? And he said, "Well, we can now measure them at the CDC and we see they're in everybody, they're in women of reproductive age, fact one. Fact two, colleagues at the NTP have shown something they are calling the phthalate syndrome." And so he explained-

   25. AHAndrew Huberman12:42

       What is NTP?

   26. SSDr. Shanna Swan12:44

       National Toxicology Program, sorry-

   27. AHAndrew Huberman12:45

       Thank you.

   28. SSDr. Shanna Swan12:46

       ... for, for using alphabet (laughs) No, quite, quite all right. ... super acro- right (laughs) .... National Toxicology Program, a governmental, you know, research center. And, um, and their job is to look at chemicals and see what is the toxicity. So it could be reproductive, it could be carcinogenicity, it could be neurotoxicity. That's what they do. And, um, so they had singled out these phthalates as being reproductively toxic, and specifically to males, and specifically when exposure i- is in utero.

   29. AHAndrew Huberman13:19

       Pregnant mom is exposed to phthalates, and somehow the fetus is disrupted.

   30. SSDr. Shanna Swan13:28

       Yes.
4. 13:30 – 19:11

   Phthalate Syndrome, Animal Data, Male Offspring

   1. AHAndrew Huberman13:30

      I'd like to know, um, is mom ingesting phthalates in the form of food? Is she inhaling phthalates? Are they landing on her skin? What are the modes of entry into the body of the mom that, um... let's just assume it goes through the placental barrier into the fetus and is impacting fetal development.

   2. SSDr. Shanna Swan13:46

      Right. So in those experiments, it was through food. But we are exposed in all those ways you mentioned. Every way that something can get into our body, phthalates get in there.

   3. AHAndrew Huberman13:58

      Mm-hmm.

   4. SSDr. Shanna Swan13:58

      But let's come back to that. Let me go to the experiment at NTP. So what, uh, they did at NTP, National Toxicology (laughs) Program, they, they fed, um, mother rats various doses of these various phthalates. And, um, and what they found was n- no changes in the females, or not a- that they found at that time. Their-

   5. AHAndrew Huberman14:20

      The female offspring?

   6. SSDr. Shanna Swan14:21

      Female offspring, sorry.

   7. AHAndrew Huberman14:22

      Mm-hmm. Mm-hmm.

   8. SSDr. Shanna Swan14:22

      But in the male offspring, they found that the genitals were, I would summarize it by saying incompletely masculinized. So I'll explain what that is. So for that, I have to g- back up and say, um, something you know, probably know very well, but I'll just explain it. The genital tract initially is a ridge. It's a single ridge. It's the same in males and females. It's not sexually dimorphic at the beginning. And then under the influence of testosterone, in a very specific window called the male programming window, in rats it stays, I think, nine to 12 of gestation. So a very short window.

   9. AHAndrew Huberman15:01

      To orient people, I think rat, mouse gestation is about 21 days or so.

   10. SSDr. Shanna Swan15:05

       Yeah. Yeah.

   11. AHAndrew Huberman15:05

       Okay.

   12. SSDr. Shanna Swan15:06

       So, so, so it's, for us it'll be early first trimester.

   13. AHAndrew Huberman15:10

       Mm-hmm.

   14. SSDr. Shanna Swan15:10

       Okay? But that comes later. So, so, um, at that time, if they feed their mother that chemical in her food, then her male offspring are born with changes in his genitals, or more likely to, right? And so what they tend to have is a, a smaller penis, um, eh, less descent of the testes, more likely to have undescended testicles. Um, there are internal changes that we didn't get into in our human study because we can't look there, but, um, the epididymis, there are changes and so on. There, the whole genital tract is altered. And the most important measure for me, as it turned out, and for humans, um, and perhaps for animals, is something that the scientists, animal scientists had studied for a long time, for actually 90-plus years, but had never been studied in humans. And that is the distance from the anus to the genitals. This collection of changes in the male genitals was given the name the Phthalate Syndrome. Now you're a physician, and you, I challenge you to think of any syndrome aside from alcohol, you know, there are fetal alcohol syndrome, of course, there's a syndrome. But, uh, note what syndrome is attached to a chemical class.

   15. AHAndrew Huberman16:42

       Just for, um, technical purposes, I'm a PhD, not a clinician. But, um-

   16. SSDr. Shanna Swan16:45

       Okay, sorry. (laughs)

   17. AHAndrew Huberman16:46

       But, but I worked on neural development for many years-

   18. SSDr. Shanna Swan16:49

       Right, right, right.

   19. AHAndrew Huberman16:49

       ... and, and-

   20. SSDr. Shanna Swan16:49

       Correct.

   21. AHAndrew Huberman16:49

       ... then prior to that, some endocrine stuff.

   22. SSDr. Shanna Swan16:51

       Yeah. Yeah.

   23. AHAndrew Huberman16:51

       So I'm, I'm, um, facile with the general terms.

   24. SSDr. Shanna Swan16:54

       Yeah.

   25. AHAndrew Huberman16:56

       Um, one that comes to mind would be, for instance, um, the thalidomide babies, right? A miscarriage, anti-miscarriage drug that changed limb development. That's a very extreme example. Um, I would say for, um, in, um, human de- normal development, what I'm most familiar with are the o- early organizing effects of androgens that convert to estrogen on external phenotype, which is basically nerd speak for, during development, the Y chromosome, uh, produces, it leads to the production of a number of genes, and eventually proteins through RNA, et cetera, that, um, are i- including testosterone and dihydrotestosterone, that in the brain organizes the brain male and causes the growth of the penis. Or organizes, meaning it is, it sets up the penis-

   26. SSDr. Shanna Swan17:48

       Yeah. Right.

   27. AHAndrew Huberman17:48

       ... to then, during puberty when the penis is exposed to testosterone and estrogen and DHT-

   28. SSDr. Shanna Swan17:53

       Right. Right.

   29. AHAndrew Huberman17:53

       It's a bunch of things, not just testosterone.

   30. SSDr. Shanna Swan17:55

       Yeah.
5. 19:11 – 27:30

   Phthalate Syndrome in Humans, Pregnancy & Babies

   1. SSDr. Shanna Swan19:11

      when, well, at this point, it was only animals, right? 'Cause John was telling me about the NTP study, which was in rats. And so I thought, "Wow." You know, I like puzzles, so my first question was, "Is this happening in humans?" You might ask that, you know? As a natural thing to ask.

   2. AHAndrew Huberman19:31

      Great question.

   3. SSDr. Shanna Swan19:32

      And then I thought, "How would we find out?" And answering that question took me 10 years, okay? And so if you think about, okay, phthalate in the mother, changes in the genitals of the offspring, connect them. How do we do that, right? So we have to start with phthalates in the mother. So how do we know that? Well, fortunately or not (laughs) , I had stored a lot of urine from pregnant women from a study that I was doing on sperm count (laughs) . I just got the women's urine coincidentally, if you will. I thought, "Well, save it." You know, it's not expensive and not hard. Minus 80 degree freezers, doesn't take a lot of room, put it in there. So I had this urine saved from pregnant women, and then I knew from John that we could look in the urine for phthalate metabolites. So these are products that the body forms when they're exposed to phthalates, and they- you can measure them in urine. So I thought, "Okay, I could get that urine. I could look at the phthalate metabolites, and then I'd know what the mother was exposed to." And based on the animal data, we have good evidence that it actually makes its way to the fetus. So then I thought, "Okay, then maybe there's a change in the babies." So then I had to get the babies. So fortunately (laughs) , I had done this study on pregnant couples, pregnant women and their partners, and I was able to call them and say, "Would you come in and let us measure your babies' genitals?" (laughs) Right? And-

   4. AHAndrew Huberman21:25

      How willing were parents to let you do that?

   5. SSDr. Shanna Swan21:27

      Yeah.

   6. AHAndrew Huberman21:27

      That seems-

   7. SSDr. Shanna Swan21:27

      Oh, they were okay. Most of them-

   8. AHAndrew Huberman21:29

      Were they?

   9. SSDr. Shanna Swan21:29

      ... were okay with that. Yeah. Yeah.

   10. AHAndrew Huberman21:30

       Mm-hmm. Mm-hmm.

   11. SSDr. Shanna Swan21:30

       Well, they trusted us, you know? They had been-

   12. AHAndrew Huberman21:32

       Sure.

   13. SSDr. Shanna Swan21:32

       ... in a study with us, and, and, you know, we were reputable. S-

   14. AHAndrew Huberman21:37

       Those babies were still, um-

   15. SSDr. Shanna Swan21:39

       Young-

   16. AHAndrew Huberman21:39

       You know.

   17. SSDr. Shanna Swan21:39

       ... but not newborns.

   18. AHAndrew Huberman21:40

       Mm-hmm.

   19. SSDr. Shanna Swan21:40

       So this was a, a while later. The, the babies that we actually got were, on average, I think about a month, uh, 12 months old.

   20. AHAndrew Huberman21:47

       Mm-hmm.

   21. SSDr. Shanna Swan21:47

       So not ideal maybe because the rats had been measured at birth, the rat genitals had been m- But that's what we could do at that time.

   22. AHAndrew Huberman21:57

       Yeah, the reason I ask is there's always the potential for ongoing phthalate exposure-

   23. SSDr. Shanna Swan22:01

       Sure.

   24. AHAndrew Huberman22:01

       ... to the newborn.

   25. SSDr. Shanna Swan22:02

       Absolutely.

   26. AHAndrew Huberman22:02

       So some, but I suppose, in either case, you're able to draw some potential link between, or potentially draw a link, I have to be careful with my language there, um, between phthalate exposure in utero and ex utero and these external biomarkers.

   27. SSDr. Shanna Swan22:18

       Yeah, I mean, given that the critical window is quite short and quite early... By the way, let me just say, when the rats, they did a lot of work on this critical window, and when the rat moms were exposed before day nine, it did nothing. And when they were exposed after day 12, it did nothing. So it was only the exposure during that critical window is very delicate, and it's, by the way, true of the brain as well. So there, you know, teasing out what is the critical window is, uh, one of the challenges that we have when we work with these chemicals. So I wasn't so much worried about exposure in the delivery room and, you know, in their feed as in the first year of life, because I knew that it was unlikely to change these measures.

   28. AHAndrew Huberman23:03

       Mm-hmm. Very important point, yeah.

   29. SSDr. Shanna Swan23:03

       Do other things, but maybe, but not these measures.

   30. AHAndrew Huberman23:05

       Mm-hmm.
6. 27:30 – 32:49

   Hyenas; Phthalate Syndrome in Males

   1. SSDr. Shanna Swan27:30

      that, that's, that's a- an er- and that I began doing some work in other, looking at other species, and it turns out that that's true in all mammalian species except two, and one is the hyena-

   2. AHAndrew Huberman27:43

      Oh, right.

   3. SSDr. Shanna Swan27:44

      ... and one is the elephant. So in the hyena, c- I'm just saying this 'cause you might, will be amu- amused by it, I think.

   4. AHAndrew Huberman27:50

      Well, I, I, um-

   5. SSDr. Shanna Swan27:51

      You know about hyenas?

   6. AHAndrew Huberman27:52

      I do. I know more about hyena genitalia than I'd like to admit.

   7. SSDr. Shanna Swan27:56

      (laughs)

   8. AHAndrew Huberman27:56

      Um, and I can tell you why after you educate us, but I'll ma- I'll keep my, um, explanation brief. But I'm very familiar with hyena genitalia.

   9. SSDr. Shanna Swan28:04

      So I, um, I have, I know Stephen Glickman who works with, uh, you might know him too, he works in Berkeley with, uh-

   10. AHAndrew Huberman28:12

       Yeah, he was my instructor when I was a graduate student at Cal.

   11. SSDr. Shanna Swan28:16

       Oh my God. (laughs)

   12. AHAndrew Huberman28:16

       And I used to run in Tilden Park, I suppose I'll tell it now, and there was a colony of-

   13. SSDr. Shanna Swan28:21

       Yeah.

   14. AHAndrew Huberman28:21

       ... wild hyenas-

   15. SSDr. Shanna Swan28:22

       Yeah.

   16. AHAndrew Huberman28:22

       But they were behind chain link.

   17. SSDr. Shanna Swan28:23

       Yes.

   18. AHAndrew Huberman28:25

       It's actually a favorite hike of mine up the Strawberry Canyon Trail.

   19. SSDr. Shanna Swan28:27

       Yeah.

   20. AHAndrew Huberman28:28

       And, um-

   21. SSDr. Shanna Swan28:29

       I did that trail too. (laughs)

   22. AHAndrew Huberman28:29

       A good friend of mine, uh, Brian Prendergast, who's now a professor at the University of Chicago, worked on the prairie voles that were also housed at that facility.

   23. SSDr. Shanna Swan28:36

       Yeah.

   24. AHAndrew Huberman28:37

       And, um, a fun thing to do was to go see the hyenas with Steve. Um, they're brutally dangerous animals, um, and Steve has tons of stories about them. We, we should probably resist our temptation to-

   25. SSDr. Shanna Swan28:52

       (laughs) Go inside.

   26. AHAndrew Huberman28:53

       ... spiral into that. May- maybe sometime I'll do a little, um, like evening chat podcast where I, I tell Steve Glickman stories. He's a delightful person. And, um, yeah, those, uh, let's just say this, the female hyenas have clitorises larger than some of the male hyena penises, and those females give birth through those clitorises-

   27. SSDr. Shanna Swan29:12

       Yes.

   28. AHAndrew Huberman29:12

       ... as we both know.

   29. SSDr. Shanna Swan29:13

       So you will not be surprised to know that the female AGD is longer than the male.

   30. AHAndrew Huberman29:19

       Right, 'cause they're heavily androgenized.
7. 32:49 – 34:22

   Sponsor: AG1

   1. SSDr. Shanna Swan32:49

   2. AHAndrew Huberman32:49

      I'd like to take a quick break and thank our sponsor, AG1. AG1 is an all-in-one vitamin mineral probiotic drink with adaptogens. I've been taking AG1 daily since 2012, so I'm delighted that they're sponsoring this podcast. The reason I started taking AG1 and the reason I still take AG1 once and often twice a day, is because it is the highest quality and most complete foundational nutritional supplement. What that means is that AG1 ensures that you're getting all the necessary vitamins, minerals, and other micronutrients to form a strong foundation for your daily health. AG1 also has probiotics and prebiotics that support a healthy gut microbiome. Your gut microbiome consists of trillions of microorganisms that line your digestive tract and impact things such as your immune system status, your metabolic health, your hormone health, and much more. So I've consistently found that when I take AG1 daily, my digestion is improved, my immune system is more robust, I rarely get sick, and my mood and mental focus are at their best. In fact, if I could take just one supplement, that supplement would be AG1. If you'd like to try AG1, you can go to drinkag1.com/huberman to claim a special offer. For this month only, November 2024, AG1 is giving away one free month's supply of omega-3 fatty acids from fish oil, in addition to the usual welcome kit of five free travel packs and a year's supply of vitamin D3 K2 with your order. Omega-3 fatty acids are critical for brain health, mood, cognition, and much more. Again, go to drinkag1.com/huberman to claim this special offer. More

8. 34:22 – 39:03

   Polycystic Ovary Syndrome (PCOS), Mothers & Female Offspring

   1. AHAndrew Huberman34:22

      Thalid exposure equates to shorter, uh, anogenital distance in males. It, it, um, was approaching the distribution in females. Um, it sounds like the, the, the distributions moved more closely together.

   2. SSDr. Shanna Swan34:35

      Yes, yes.

   3. AHAndrew Huberman34:36

      Right?

   4. SSDr. Shanna Swan34:36

      Yes. Although it wasn't the females that moved.

   5. AHAndrew Huberman34:39

      Sorry, the male distribution, um-

   6. SSDr. Shanna Swan34:41

      Became more like the female. Yeah.

   7. AHAndrew Huberman34:42

      ... became more, uh-

   8. SSDr. Shanna Swan34:43

      Right. Feminine.

   9. AHAndrew Huberman34:44

      ... I shouldn't say feminized, but more female-like in its-

   10. SSDr. Shanna Swan34:46

       Yeah. And they, but these boys also had smaller penises, less descent of the testes, um, smaller scrotums. Uh, so they were smaller. You know, everything was in their genital areas.

   11. AHAndrew Huberman34:56

       Are all the secondary sex characteristics of puberty in males, Adam's apple, facial hair growth, um, thickening of the vocal cords, therefore lowering the voice, et cetera, are those all later activating effects of hormones or are there precursors to those that are present in, in, um, in males? Because in mice as I recall, like, like I couldn't, I couldn't tell you that... Like, we call it in the laboratory, people always chuckle at this, but it's, like, sexing the animals when you, you know, uh, l- look to determine if it's a male or female. Uh, when they're, when they're really young, you have to, like, look carefully (laughs) at first, right? And then you get pretty good at it. Um, as they get older, it gets easier. But when the mice are, um, uh, you know, feet down, back up, you know, you can't really, you can't really tell.

   12. SSDr. Shanna Swan35:47

       Right.

   13. AHAndrew Huberman35:47

       You can't, you can't really tell.

   14. SSDr. Shanna Swan35:48

       Right, right.

   15. AHAndrew Huberman35:49

       The, the... As the mice get older, their testicles become visible in the males-

   16. SSDr. Shanna Swan35:52

       Right.

   17. AHAndrew Huberman35:52

       ... from, even from above.

   18. SSDr. Shanna Swan35:54

       Right.

   19. AHAndrew Huberman35:54

       But, you know, as far as I know, there aren't really external markers, so you may have found the one truly external biomarker of maleness.

   20. SSDr. Shanna Swan36:02

       Of maleness. And, and so I, I, I do wanna say one thing about females 'cause then that'll lead me to my conclusion about the role of this measure. Um, so if the mother is exposed to more testosterone than expected, you might expect that her female offspring would have a more male anogenital distance.

   21. AHAndrew Huberman36:27

       Is that the case?

   22. SSDr. Shanna Swan36:28

       Yes.

   23. AHAndrew Huberman36:29

       So it's a bidirectional effect.

   24. SSDr. Shanna Swan36:30

       Yes.

   25. AHAndrew Huberman36:31

       Can we also presume that if the mother either secretes or is exposed to more androgen, then the males can become hypermale?

   26. SSDr. Shanna Swan36:39

       No. We'd never... I don't know what that would be. We never saw anything that would be hypermale. Um, so the, the yes I said to you was the result of a study, uh, where we looked at the girls born to women with PCOS. So women with PCOS, as you know, have-

   27. AHAndrew Huberman36:59

       Mm-hmm.

   28. SSDr. Shanna Swan36:59

       ... ex- excess testosterone.

   29. AHAndrew Huberman37:00

       Polycystic ovarian sy-

   30. SSDr. Shanna Swan37:01

       Cystic ov- Oh, sorry. (laughs)
9. 39:03 – 45:03

   Anogenital Distance & Sperm Count

   1. SSDr. Shanna Swan39:03

      Yes?

   2. AHAndrew Huberman39:03

      Yeah. What, what is the impact of this early androgen exposure in, to female offspring, or, um, let's just say reduction in functional androgen exposure to male offspring? The reason I'm using these, uh, you know, loop de loop languages is, as you probably know, but for the audience, uh, not trying to complicate things here, but a lot of the masculinizing effects of hormones in fetal development is actually testosterone that's converted into estrogen. So it can get pretty tricky.

   3. SSDr. Shanna Swan39:35

      Right.

   4. AHAndrew Huberman39:35

      And, um, but maybe for sake of simplicity today, we'll just stick with androgen effects on masculinization with the understanding that some of those effects-

   5. SSDr. Shanna Swan39:46

      Are biased.

   6. AHAndrew Huberman39:46

      ... are the consequence of testosterone being converted into estrogen.

   7. SSDr. Shanna Swan39:50

      Right.

   8. AHAndrew Huberman39:50

      It's just that people form such strong associations falsely that, you know, testosterone is-

   9. SSDr. Shanna Swan39:56

      Male.

   10. AHAndrew Huberman39:57

       ... male, maleness-

   11. SSDr. Shanna Swan39:57

       Mm-hmm.

   12. AHAndrew Huberman39:57

       ... and that's not true. And, and, and estrogen is femaleness and they bo- and it, it-

   13. SSDr. Shanna Swan40:01

       Right.

   14. AHAndrew Huberman40:01

       ... just gets really murky. But for, for the time being, um, you identified an external biomarker of fetal androgen, AKA masculinization via the mother.

   15. SSDr. Shanna Swan40:16

       That's right.

   16. AHAndrew Huberman40:17

       Got it.

   17. SSDr. Shanna Swan40:18

       Okay. So then we asked the question you've asked and many people asked, who cares? (laughs) What, what, why would we th- worry about a boy having a slightly smaller anogenital distance?

   18. AHAndrew Huberman40:35

       Well, I can tell you there are many boys that are probably worried about it right now.

   19. SSDr. Shanna Swan40:38

       Right, right. (laughs)

   20. AHAndrew Huberman40:39

       (laughs) They probably got the ruler and the calipers out right now. Just, you know. Um-

   21. SSDr. Shanna Swan40:44

       But I'm gonna answer that question.

   22. AHAndrew Huberman40:46

       Right.

   23. SSDr. Shanna Swan40:47

       So I told you that our kids are too young. They're not producing sperm right now, right? So we had to go to an adult population, right? And so we went to a s- population of college students in Rochester, New York. And what we did there was make an assumption which is based on animal data. It's true in animals. We've been following the animal path here all along. So in the animals, my colleague, Earl Gray, who did these studies said-

   24. AHAndrew Huberman41:20

       His name is Earl Gray?

   25. SSDr. Shanna Swan41:22

       Yeah.

   26. AHAndrew Huberman41:22

       That's cool.

   27. SSDr. Shanna Swan41:23

       Yeah. (laughs) Um, he said, "AGD is forever." S-

   28. AHAndrew Huberman41:29

       Anogenital distance is forever?

   29. SSDr. Shanna Swan41:31

       Now, what that means is it's not like your anogenital distance today is what it was when you were born. Of course, you're a bigger person, but that means adjusted for body size, right? So if you assume that AGD is forever, if you're born with a short for your size AGD, then when you're 20, you'll have a short for your size AGD. Okay? Can we assume that?

   30. AHAndrew Huberman41:53

       Mm-hmm.
10. 45:03 – 49:24

    Sperm Count & Fertility

    1. AHAndrew Huberman45:03

       So it sounds like, um... Oh, and may I ask, were the sperm counts that were on the, let's just say the lower, um, like the lower quartile, were the quote unquote "lower sperm counts" like functionally lower? 'Cause I always wonder about this. Like I, it's come up in a number of discussions like with Robert Sapolsky, with Mike Eisenberg, and now I'm asking you. When we hear that sperm counts are going down, are they going down to the point where fertility is, is impacted? That's really the, the, one of the-

    2. SSDr. Shanna Swan45:33

       Yeah.

    3. AHAndrew Huberman45:33

       ... I think functional questions.

    4. SSDr. Shanna Swan45:35

       So I'm gonna, let's lay aside the question of AGD, right? 'Cause that's, uh, really interesting, but let's talk about sperm count (laughs) .

    5. AHAndrew Huberman45:44

       Yeah.

    6. SSDr. Shanna Swan45:44

       Okay. Okay. So, um, if you, there's a, a beautiful study, um, among pregnancy planners out of Denmark, um, quite a long time ago, um, and in that study, what they did was take couples that were trying to conceive, that had never, or not recently, I can't remember, used oral contraceptives, and then they saw what the sperm count was and how long it took them to conceive, right? Time to pregnancy in relation to sperm. And what they showed is a really interesting curve which has never been corrected, to my knowledge. It's, it's, it's what I use and what I think people use. Which is that if you... I wish I could draw it here. I wish I had a bl- you should have a board, a whiteboard. (laughs)

    7. AHAndrew Huberman46:35

       The problem is a lot of people are listening, but maybe we, you know-

    8. SSDr. Shanna Swan46:38

       Yeah, I know, I know, I know.

    9. AHAndrew Huberman46:38

       ... we can, we can talk people through it.

    10. SSDr. Shanna Swan46:39

        Yeah. Yeah.

    11. AHAndrew Huberman46:40

        Sorry.

    12. SSDr. Shanna Swan46:40

        So, so just think about, um, a curve where you go all the way down to zero, that would be no sperm, um, and then as, the ch- probability of conceiving is zero. So you're looking at sperm count along the, you know, is the x-axis, and months to conception, um, and, um, what you see is that if you have no sperm you don't have no conception. If you go up to around 40, 45, there's a steep increase. So the more sperm you have-

    13. AHAndrew Huberman47:11

        40, 45 million?

    14. SSDr. Shanna Swan47:13

        Mi- million per milliliter.

    15. AHAndrew Huberman47:14

        And this is million per milliliter, uh, j- so just pure concentration, not number of motile sperm. This is just-

    16. SSDr. Shanna Swan47:20

        That's it. Right.

    17. AHAndrew Huberman47:20

        ... how many sperm. Okay, we're not-

    18. SSDr. Shanna Swan47:21

        That's right.

    19. AHAndrew Huberman47:21

        ... talking about quality, we're just talking about number.

    20. SSDr. Shanna Swan47:22

        No. No. No. Just the number.

    21. AHAndrew Huberman47:23

        Okay.

    22. SSDr. Shanna Swan47:23

        And, and when you have 45 to 50 million per milil- liter, and below, it matters a lot what your sperm count is. You know, people say-

    23. AHAndrew Huberman47:32

        Mm-hmm.

    24. SSDr. Shanna Swan47:32

        ... it doesn't matter. Yeah, if you get in this range where the probability of conception is dropping off really rapidly-

    25. AHAndrew Huberman47:38

        Mm-hmm.

    26. SSDr. Shanna Swan47:39

        ... it matters a lot.

    27. AHAndrew Huberman47:40

        Mm-hmm.

    28. SSDr. Shanna Swan47:40

        And then there around 45 to 50 it starts to level off, and then after that, after, certainly after 100, c- probably 75, it doesn't matter at all.

    29. AHAndrew Huberman47:50

        Hundr- uh, so 100 million sperm per milliliter-

    30. SSDr. Shanna Swan47:54

        Yes.
11. 49:24 – 51:11

    Sponsor: Function

    1. AHAndrew Huberman49:24

       I'd like to take a quick break and thank one of our sponsors, Function. I recently became a Function member after searching for the most comprehensive approach to lab testing. While I've long been a fan of blood testing, I really wanted to find a more in-depth program for analyzing blood, urine, and saliva to get a full picture of my heart health, my hormone status, my immune system regulation, my metabolic function, my vitamin and mineral status, and other critical areas of my overall health and vitality. Function not only provides testing of over 100 biomarkers, key to physical and mental health, but it also analyzes these results and provides insights from top doctors on your results. For example, in one of my first tests with Function, I learned that I had too high levels of mercury in my blood. This was totally surprising to me. I had no idea prior to taking the test. Function not only helped me detect this, but offered medical doctor informed insights on how to best reduce those mercury levels, which included limiting my tuna consumption, because I had been eating a lot of tuna, while also making an effort to eat more leafy greens and supplementing with NAC, N-acetylcysteine, both of which can support glutathione production and detoxification, and worked to reduce my mercury levels. Comprehensive lab testing like this is so important for health. And while I've been doing it for years, I've always found it to be overly complicated and expensive. I've been so impressed by Function, both at the level of ease of use, that is getting the tests done, as well as how comprehensive and how actionable the tests are, that I recently joined their advisory board, and I'm thrilled that they're sponsoring the podcast. If you'd like to try Function, go to functionhealth.com/huberman. Function currently has a wait list of over 250,000 people, but they're offering early access to Huberman Lab listeners. Again, that's functionhealth.com/huberman to get early access to Function.

12. 51:11 – 58:19

    Sperm Count Decline

    1. AHAndrew Huberman51:11

       We were onto the fact that sperm counts are dropping. There's a relationship to anogenital distance, and there's a relationship between anogenital distance and phthalate exposure.

    2. SSDr. Shanna Swan51:19

       Yeah.

    3. AHAndrew Huberman51:19

       And then I asked the question, you know, okay, we're hearing about sperm counts dropping, but is it functionally relevant? Are, is that one of the reasons why fertility is dropping? And we've also got the female side where we've got women with, uh, elevated androgens. So we can talk about that a little bit later, but, um, and then of course we have the socio-, uh, the sociobiology, uh, piece where people are opting out, um, or it's also economics in some cases, um, opting out of having kids.

    4. SSDr. Shanna Swan51:51

       Right.

    5. AHAndrew Huberman51:51

       Um...

    6. SSDr. Shanna Swan51:52

       So let's go back to sperm count 'cause we haven't really talked about that.

    7. AHAndrew Huberman51:54

       Mm-hmm.

    8. SSDr. Shanna Swan51:55

       It's a kind of a different path, and my introduction into phthalates was not through sperm count, right? It was through this question of my colleague asking me, uh, you know, "You should look at this." I'm challenged and I looked at it, and that was really, really interesting journey that I went on. Okay, so that, but there was a separate, for a while, journey that I was on, and that started in the late 1990s when, um, I was asked to join a committee of the National Academy of Sciences. And that committee was assembled to look at the question of whether hormonally active chemicals, endocrine-disrupting chemicals in the environment posed a threat to human health.

    9. AHAndrew Huberman52:41

       Mm-hmm.

    10. SSDr. Shanna Swan52:42

        Because at that time, it was like, "Well, yeah, we hear about this, but should we care?" Right? And so that committee wanted to consider a study that had come out of Denmark a few years earlier, which claimed that sperm count had dropped 50% in 50 years.

    11. AHAndrew Huberman53:04

        Wow. That's a huge drop.

    12. SSDr. Shanna Swan53:07

        That's what, we're seeing worse than that, by the way, now. So, okay, they said to me, I was the only statistician on the panel, "Would you look at this and see if we need to consider this in our deliberations?" And as I mentioned, I'm skeptical, and I looked at it and I thought, "Uh, I don't think so." That was my initial reaction. And that was because, uh, first of all, I didn't know who had written this. I just saw it in a journal and, and it was n- not very big and not very many figures, not very m- much data. And I thought of it and I thought, "Well, that's, that's a big claim for a little" (laughs) "a little paper," you know? Um, but I'll look at it 'cause it's important. And so what I did then was to think about all the factors that we epidemiologists call confounders.

    13. AHAndrew Huberman54:00

        Mm-hmm.

    14. SSDr. Shanna Swan54:01

        Things that might have caused that decline if it wasn't real biologically, right?

    15. AHAndrew Huberman54:07

        Mm-hmm.

    16. SSDr. Shanna Swan54:08

        And so we could think of some of them together. Um, you know, maybe the method of counting sperm had changed so that later methods counted fewer sperm in the same sample. That's certainly possible, right? Um, but it turned out that wasn't the case 'cause they actually had all used the same method. Um, and maybe the men had changed, so maybe it, there's all... You can't get a sperm count at random. You have to get somebody to (laughs) volunteer, right? So who were these men or were they very different, you know, in the early part of the study and the late part of the study in a way that maybe in the late part of the study, there were men with lower sperm count and they were more concerned, you know? Maybe they were more obese. That's pretty plausible. Obesity is related to s- same sperm count, fertility. Um, and maybe they smoked more and maybe... And so on and so forth, right? So what I did was to get the 61 studies, go through them, and try to extract information on all the factors that could explain the decline. So I created a multi-variable model and ran that model. And to my astonishment, when I was done, the slope of the decline was exactly the same to the first decimal place.... it had not explained anything. (laughs) And I was like, "Oh my God. This looks like it might be real."

    17. AHAndrew Huberman55:42

        And, and for those listening, what Dr. Swan is describing is, being the excellent scientist that she is, she went and looked for all the things that could impact the result that were not related to what the main conclusion seemed to be, which is that sperm counts were going down, o- over time.

    18. SSDr. Shanna Swan56:01

        Right.

    19. AHAndrew Huberman56:01

        Right? And, uh, this is really important, um, to ... because I think what we're talking about here in parallel to the main conversation is how to do really great science, especially in human populations that are out there living. You know, some of these men probably s- you know, smoke some cannabis. I'm not saying that reduces sperm count. Might reduce sperm moti- motel- motility ...

    20. SSDr. Shanna Swan56:21

        (laughs)

    21. AHAndrew Huberman56:21

        ... however. We covered that in the podcast. Now that all the cannabis folks go, "Well, uh, you know, so-and-so got so-and-so pregnant when they were doing ... smoking a lot of weed." And I always say, "Okay, well, there are a number of other factors," right? You know, but alcohol, there's, um, frequency of ejaculation, right? The, the requirement to have abstained for 48 to 72 h- hours to up to five days prior, you know, et cetera. All, all these, these factors that men may or may not faithfully report, but you assume that if some are telling the truth and some aren't, that there's an equal distribution of that. So all the different things.

    22. SSDr. Shanna Swan56:54

        Right.

    23. AHAndrew Huberman56:55

        Right? This is so very different than looking at, for instance, um, ovarian reserve, like the, the number of eggs, where you use ultrasound and you use AMH levels, and, um, sure, things can impact that, but it's a little different than when taking, uh-

    24. SSDr. Shanna Swan57:11

        Yeah.

    25. AHAndrew Huberman57:12

        ... sperm counts.

    26. SSDr. Shanna Swan57:12

        Right.

    27. AHAndrew Huberman57:12

        So thank you for doing the, the study so carefully and for repeating them so many times. I mean, many of the studies that you've done are, are, um, you, you've done follow-up on these sperm count studies across multiple years. You know, as you said, the first, uh, study was in 1992, then you did one in 2017, then there was one again, and there was an update I noticed online. So you are extremely thorough. You, you ... And, and it probably ref- reflects your, um, early training in math and statistics and probability theory.

    28. SSDr. Shanna Swan57:40

        Right.

    29. AHAndrew Huberman57:40

        You're not somebody to just kinda go in and go, "Oh yeah, like, in these people that eat a few too much of this, then there's-"

    30. SSDr. Shanna Swan57:45

        (laughs)
13. 58:19 – 1:04:12

    Sperm Quality & Pesticides

    1. AHAndrew Huberman58:19

    2. SSDr. Shanna Swan58:19

       So, so when I saw that and actually did another study to select my own studies and not accept her 61 studies that had been published-

    3. AHAndrew Huberman58:29

       Mm-hmm.

    4. SSDr. Shanna Swan58:30

       ... that Elizabeth Carlson had published. Uh, so new studies, came up to more recent times, went back further, um, did it again, found exactly the same thing. Okay, so there were three, you know, three looks at that, and I thought, "Okay, I'm gonna accept this now." This is sperm count is declining.

    5. AHAndrew Huberman58:47

       Mm-hmm.

    6. SSDr. Shanna Swan58:48

       And why? I turned to the why. Okay? Because up until now, we hadn't said anything about why. We just said, "Is it doing that?" Yes. Okay, if it ... Now, we believe it is declining, why? And so then I thought quite a lot and talked to people and ruled out genetics because it was too fast. It's two generations is too fast, 50 years, two generations. So if it's not genetics, then it's environment. And so what is it about the environment that could do this? So I asked, "Okay, in the environment, there could be things that are making sperm decline." So if you think about how you might look at that, you might design the study that I designed next, which was another study. And the ... By the way, this preceded the AGD, so it just ... So we had four cities in the United States that we picked with different environments, and then we got men to come in and we used the same equipment at each place. We used the same method of selection th- selecting the man. The technicians were trained centrally at UC Davis. We had very good quality control, so samples were sent around every quarter to make sure that everybody was measuring things the same way. Uh, we didn't want drift, right?

    7. AHAndrew Huberman1:00:09

       Mm-hmm.

    8. SSDr. Shanna Swan1:00:09

       And then we got their urine, um, and that's how I had those urine samples. So what ... If you wanted to do this study and you wanted to get a representative sample of men, where would you go? Because you can't ... I can't ask a guy on the street to give me his semen sample, right? I mean, (laughs) it's not, it's not something you get very, you know. So I thought, "How can I get a representative sample and ... which would teach me something about a larger population," called the parent population. So here's a sample. It should represent the parent. So how do I ensure that? And what I decided was to sample partners of pregnant women.

    9. AHAndrew Huberman1:00:48

       Mm-hmm.

    10. SSDr. Shanna Swan1:00:48

        Because pregnant women all come to medical care, almost all, and if their partners will give a semen sample, then we have a representative sample.

    11. AHAndrew Huberman1:00:57

        Mm-hmm.

    12. SSDr. Shanna Swan1:00:57

        And we know what we're looking at. So that's what we did. So this is a ... The semen study is the study of partners of pregnant women. And, um, and of course they'll have slightly higher semen quality 'cause they got their partner pregnant, but ... Um, and so we had their urine, we had their blood, and, um, we looked at their semen quality, and then we decided to look at pesticides. And the reason we look at pesticides, um, was because there was a lot of gradation across our four centers in pesticide use. And what we found was really extraordinary, that (clears throat) men who were living in central Missouri, where I was living at the time-... who were in the middle of a agricultural belt, where there was spraying all the time for soybeans and so on. Um, those men had half as many moving sperm as men in Minneapolis.

    13. AHAndrew Huberman1:01:59

        Whoa.

    14. SSDr. Shanna Swan1:02:00

        Whoa. Huge, right? And then we went one step further and within Missouri, we looked at a sample of men who had very high sperm parameters and very low sperm parameters, and showed that five pesticides were significantly higher in the men with the low sperm parameters. That include motility, morphology, you know, all, all

    15. AHAndrew Huberman1:02:26

        So these are pesticides that are being sprayed in the air on crops. You mentioned soybeans. What other, what other types of crops?

    16. SSDr. Shanna Swan1:02:32

        I don't know.

    17. AHAndrew Huberman1:02:33

        Okay.

    18. SSDr. Shanna Swan1:02:33

        I don't remember. (laughs) I'm not gonna lie.

    19. AHAndrew Huberman1:02:35

        (laughs) But so, so plant and fruit crops, presumably.

    20. SSDr. Shanna Swan1:02:37

        Uh, it was, yeah, whatever, whatever they were growing in Columbia, Missouri-

    21. AHAndrew Huberman1:02:41

        Mm-hmm.

    22. SSDr. Shanna Swan1:02:41

        ... at that time. But-

    23. AHAndrew Huberman1:02:42

        And, and just to make sure I understand. It's not that the men need-

    24. SSDr. Shanna Swan1:02:47

        Soybeans. Corn and soybeans.

    25. AHAndrew Huberman1:02:48

        Corn and soybeans.

    26. SSDr. Shanna Swan1:02:49

        Yeah.

    27. AHAndrew Huberman1:02:49

        But we're not talking about eating corn and soybeans.

    28. SSDr. Shanna Swan1:02:51

        No.

    29. AHAndrew Huberman1:02:51

        We're talking about living in an area where pesticides are being used by, I guess they're called-

    30. SSDr. Shanna Swan1:02:57

        But actually, we-
14. 1:04:12 – 1:09:00

    Atrazine, Amphibians, Sexual Dimorphism, Behavior

    1. AHAndrew Huberman1:04:12

       um, theme there would be, uh, maybe we could take a moment and talk about Atrazide and its effect on, uh, male sexual behavior in amphibia. And we'll come, um, come back to-

    2. SSDr. Shanna Swan1:04:23

       (laughs)

    3. AHAndrew Huberman1:04:23

       ... the, the, the sperm studies because-

    4. SSDr. Shanna Swan1:04:25

       Sure. Sure.

    5. AHAndrew Huberman1:04:26

       ... um, when I was a graduate student at UC Berkeley, I had the wonderful experience of taking a course from the now, I think you mentioned he's a dean. There are multiple deans on campuses. Tyrone Hayes is a wonderful researcher, um, who established a link through his research between atrazine exposure and, um, male sexual behavior of amphibia.

    6. SSDr. Shanna Swan1:04:48

       Yes.

    7. AHAndrew Huberman1:04:49

       Could you elaborate on that result?

    8. SSDr. Shanna Swan1:04:52

       Yeah. So, Tyrone first caught frogs in the wild, uh, in environments that were more or less exposed to atrazine, and showed effects on development and sexual behavior. Then he, in his lab, he actually exposed them. So he knew exactly who was exposed and to how much. And he showed that the, and I can't tell you what percent or what, you know, huh, but a significant number of frogs exposed to this pesticide, atrazine, chose to mate with other male frogs.

    9. AHAndrew Huberman1:05:27

       Tried to mate with other male frogs. Presumably unsuccessfully.

    10. SSDr. Shanna Swan1:05:30

        Well, they cl- they mounted them.

    11. AHAndrew Huberman1:05:32

        Mm-hmm.

    12. SSDr. Shanna Swan1:05:32

        He has photos of them male, males mounting males.

    13. AHAndrew Huberman1:05:35

        And so presumably this is a neural change that occurred.

    14. SSDr. Shanna Swan1:05:40

        Right.

    15. AHAndrew Huberman1:05:40

        Neuroendocrine change.

    16. SSDr. Shanna Swan1:05:41

        Right.

    17. AHAndrew Huberman1:05:41

        But ultimately neural since mounting behavior is controlled by w- actually we now know the, the, um, hypothalamic nuclei that control this. David Anderson, who's been on this podcast, has people in his laboratory that in- including a former graduate student of mine, um, uh, working on, on this specific issue of what the, what the, the circuitry, um, is. Um, that's a remarkable result. It's been kind of, um, you know, used and misused out there in the, in the, in the media and in popular culture. Um, but if nothing else, it suggests that the organization of the neural circuits and neuroendocrine pathways that control, um, sexual, I don't wanna say partner because it is mating thing. There's, frogs aren't monogamous, but, um, uh, sexual preference are, um, significantly impacted by this, by this atrazine.

    18. SSDr. Shanna Swan1:06:37

        Yes. And, and it suggests that, that there are other environmental chemicals can as well. And we, I don't know how, if we'll have time to go there, but I did w- work on neurodevelopmental outcomes in relation to prenatal phthalate exposure. And so I think w- the overarching idea (coughs) here is that the brain, like the genitals, is sexually dimorphic. And there's many people, by the way, who will take offense at that.

    19. AHAndrew Huberman1:07:07

        Really?

    20. SSDr. Shanna Swan1:07:07

        Yeah.

    21. AHAndrew Huberman1:07:08

        I think there's, I mean, going back to the-

    22. SSDr. Shanna Swan1:07:10

        (laughs) I know.

    23. AHAndrew Huberman1:07:10

        ... the work of Frank Beach in the-

    24. SSDr. Shanna Swan1:07:12

        I know. (laughs)

    25. AHAndrew Huberman1:07:12

        ... uh, psychology department at UC Berkeley-

    26. SSDr. Shanna Swan1:07:13

        I know.

    27. AHAndrew Huberman1:07:14

        ... um, showed this in beagles. It's been, it's been shown in pretty much every species-

    28. SSDr. Shanna Swan1:07:18

        I know. But I'll just tell you that-

    29. AHAndrew Huberman1:07:19

        But, but it's not a better/worse. I think this is what people need to hear.

    30. SSDr. Shanna Swan1:07:21

        No. Yeah.
15. 1:09:00 – 1:14:08

    Preschoolers, Phthalate Exposure, Sexually Dimorphic Behaviors

    1. SSDr. Shanna Swan1:09:00

       there is a, a very simple outdated questionnaire, and it's play behavior. It's called the PSAI.

    2. AHAndrew Huberman1:09:09

       Mm-hmm.

    3. SSDr. Shanna Swan1:09:09

       It's been used for years. Have you h- heard or have you heard-

    4. AHAndrew Huberman1:09:12

       This rough and tumble play?

    5. SSDr. Shanna Swan1:09:13

       Yes.

    6. AHAndrew Huberman1:09:13

       Yeah.

    7. SSDr. Shanna Swan1:09:14

       Yes. And there are 24 questions on there, and they are sexually dimorphic, I guess you could say, that they're, you know, my child likes to play with dolls. My child likes to play dress up. My child likes to play rough and tumble, uh, et cetera. And we gave that questionnaire to our population, um, and looked at the answers, uh, that the mothers gave, both in our population, by the way, and a Swedish population of a colleague there, uh, Carl, um, uh, Bornehag.

    8. AHAndrew Huberman1:09:48

       Hm.

    9. SSDr. Shanna Swan1:09:48

       And... Gustav Bornehag. And, and, um, what we found, higher phthalate levels, these anti-androgenic phthalates were expo- you know, were associated with less masculine male typical play in our male boys. So, you know-

    10. AHAndrew Huberman1:10:07

        This is phthalate exposure to the-

    11. SSDr. Shanna Swan1:10:09

        In utero.

    12. AHAndrew Huberman1:10:10

        ... to the mom. Baby is born. In the young human child-

    13. SSDr. Shanna Swan1:10:15

        Four, four, yeah, four year- I think it was four years of age.

    14. AHAndrew Huberman1:10:17

        Four years of age, l- less rough and tumble type play-

    15. SSDr. Shanna Swan1:10:20

        That's right.

    16. AHAndrew Huberman1:10:21

        ... among the boys whose mothers were exposed to more phthalates during a critical period of development.

    17. SSDr. Shanna Swan1:10:26

        Now you can see that's a politically loaded (laughs) issue now.

    18. AHAndrew Huberman1:10:30

        Yeah.

    19. SSDr. Shanna Swan1:10:30

        You know?

    20. AHAndrew Huberman1:10:30

        I mean, you know, I-

    21. SSDr. Shanna Swan1:10:32

        It's a-

    22. AHAndrew Huberman1:10:32

        Yeah, i- well, I think we're... I mean, let's, let's, let's have some fun with this in, in, in the scientific sense. The, the notion of dimorphism is, you know, okay, male and female brains are different, right? Which I... and male female defined in those, almost all those studies as presence of a Y chromosome. And then people say, "Well there's some, there's XYY and then there's XXY." Okay, but most of the time you're talking about XX chromosome or X Y chromosomes at birth. Forget e- everything else for the moment. These are always distributions.

    23. SSDr. Shanna Swan1:11:02

        Sure.

    24. AHAndrew Huberman1:11:02

        This is what I think people need to know. We're not talking about... Th- these are not t- this is not, uh, you know, two hills of data separated by a valley. These are overlapping distributions.

    25. SSDr. Shanna Swan1:11:12

        Correct.

    26. AHAndrew Huberman1:11:13

        Right? So you get males with a, quote unquote, "female-like distribution," you get females with a, quote unquote, "male-like distribution." And I think as long as we acknowledge that, then we're just talking statistics.

    27. SSDr. Shanna Swan1:11:24

        Right.

    28. AHAndrew Huberman1:11:24

        We're not w- we're not placing any cultural or, um, any value on it really whatsoever.

    29. SSDr. Shanna Swan1:11:31

        Right, right.

    30. AHAndrew Huberman1:11:31

        Right.
16. 1:14:08 – 1:24:52

    Tools: Lowering Exposure to Endocrine Disruptors, Fertility

    1. AHAndrew Huberman1:14:08

       because I know people are wondering, and I'm wondering, what are some non-pesticide sources of phthalates-

    2. SSDr. Shanna Swan1:14:16

       Oh.

    3. AHAndrew Huberman1:14:16

       ... that, um, we have agency over, that we can take control over?

    4. SSDr. Shanna Swan1:14:19

       Right. So let me ju- uh, correct you. It's not that sources of phthalates necessarily. Pesticides, there are phthalates in pesticides.

    5. AHAndrew Huberman1:14:30

       Mm-hmm.

    6. SSDr. Shanna Swan1:14:30

       Um, but that's not the worst player in, um, the, in the story. (laughs) If you look at the different classes of exposures that are hormonally active, right? Pesticides are, phthalates are, bisphenols, like bisphenol A.

    7. AHAndrew Huberman1:14:51

       BPA.

    8. SSDr. Shanna Swan1:14:51

       BPA.

    9. AHAndrew Huberman1:14:53

       Yeah.

    10. SSDr. Shanna Swan1:14:53

        Certain metals are. There's the PFAS chemicals. There's all these different classes, right?

    11. AHAndrew Huberman1:14:58

        Mm-hmm.

    12. SSDr. Shanna Swan1:14:59

        And if we wanna go, excuse me, into what in our daily life exposes us to these things, that's another story-

    13. AHAndrew Huberman1:15:08

        Mm-hmm.

    14. SSDr. Shanna Swan1:15:10

        ... that, um, we, we can talk about. But they're gonna be different depending on the class, right?

    15. AHAndrew Huberman1:15:15

        So let's, um, throw our arms around all of those for the moment, and I'll just ask you, given that you're an expert in this area, what are the top three to five sources of endocrine disruptors that we have agency over? And let's forget about pregnancy for the moment, since we're all out of the womb if we're listening to this. Um, some people will be pregnant as they listen to it. But, um, would you say it's, you know, drinking out of plastic bottles? Is it laundry detergent? Um, is it, you know, rubber tires that are cascading down on us through the air and we're inhaling them? I mean, presumably all of the above, but what are, which ones that we have agency over do you think are the most, let's just say, concerning, where people could make better choices?

    16. SSDr. Shanna Swan1:16:07

        Um, I would say foodborne exposures. Exposures in the food, in the food packaging, in the food storage, in the food, in the cooking u- utensils. Um, we can go through the various things, but, um, we're doing that all the time. (laughs) We're, you know, we're eating all the time. We're getting food into us, and these are bringing in, in a very, you know, in a way that we have some control over, some agency over.

    17. AHAndrew Huberman1:16:39

        Mm-hmm.

    18. SSDr. Shanna Swan1:16:40

        Uh, you know, we can make changes in our foods. Um, very close to that is drink. You know, food and beverage. Um, so I... First of all, I've talked about this a lot, I've written about it in my book. I'm also, as you know, involved in a movie where, in the movie, that might be a good time to talk about that.

    19. AHAndrew Huberman1:17:03

        Sure.

    20. SSDr. Shanna Swan1:17:03

        What, what we do in the movie, the movie is about six couples that are infertile. Okay? They haven't been able to conceive in 12 months. That's the definition. And, um, then a company that I work with, Million Marker out of Berkeley, has a trained staff that interviews them. Not only them, but anyone who signs into (laughs) this company, interviews them, and asks them what they use. What do they use for their face, facial care? What do they use for their shampoo? What do they use for their cleaning products, and their laundry detergent, and their, what do they store their food in? And on and on and on. So there's this long inventory that they take of all products that people are aware of using. Okay? And, um, based on that, we identify likely bad players in the list. So, how we do that is another, you know, we can talk about that later. But, um, then, in the film, and in this little, it's actually an experiment that I designed, and we're, called an intervention. And we are then intervening in their exposures by changing out these things that they told us. So we will tell them, you know, "Don't use any product with fragrance," for example. That's a major source of exposure to phthalates.

    21. AHAndrew Huberman1:18:29

        Any product?

    22. SSDr. Shanna Swan1:18:30

        Any fragrance product.

    23. AHAndrew Huberman1:18:31

        So-

    24. SSDr. Shanna Swan1:18:32

        If fragrance is added-

    25. AHAndrew Huberman1:18:32

        ... no perfume, no lotions.

    26. SSDr. Shanna Swan1:18:34

        Right.

    27. AHAndrew Huberman1:18:35

        Soap with fragrance.

    28. SSDr. Shanna Swan1:18:36

        Right.

    29. AHAndrew Huberman1:18:37

        Even essential oil fragrances like lavender?

    30. SSDr. Shanna Swan1:18:38

        Essential oil is a tricky...
17. 1:24:52 – 1:30:07

    Tools: BPA, BPS, BPF & Can Linings; Drinkware; Plastics & Microwave

    1. SSDr. Shanna Swan1:24:52

    2. AHAndrew Huberman1:24:52

       Mm-hmm. When it comes to reducing BPA exposure-

    3. SSDr. Shanna Swan1:24:55

       Yeah.

    4. AHAndrew Huberman1:24:55

       ... and some of these forever chemicals-

    5. SSDr. Shanna Swan1:24:57

       Yeah.

    6. AHAndrew Huberman1:24:57

       ... um, that you mentioned, um, seems like reducing, uh, fluid intake from plastic vessels is gonna be k- number one.

    7. SSDr. Shanna Swan1:25:06

       The primary source of BPA is in the lining of cans. So any drink or soup or anything that comes in a can is going to be, um...

    8. AHAndrew Huberman1:25:18

       Any can. All cans.

    9. SSDr. Shanna Swan1:25:20

       Any can, unless it's a high-end, i- you know, elite company that's made the change from BPA to an alternative lining. And they'll say that.

    10. AHAndrew Huberman1:25:30

        Mm-hmm.

    11. SSDr. Shanna Swan1:25:31

        So, and by the way, BPA has some bad relatives, um, such as BPS and BPF. And, and maybe you, you'd be interested in this story. So when it came out that BPA was, um, estrogenic, which is what it is, um, and by the way, it's kind of the evil twin of phthalates, because phthalates are anti- a- androgenic and BPA is estrogenic, and phthalates make plastic soft and BPA makes plastic hard. You don't want either. Okay. So, when this came out that this was a bad thing, um, the manufacturers started selling things that say BPA free. I'm sure you've seen that.... the trick is that instead of BPA, they use BPS-

Episode duration: 2:18:02