The Surprising Link Between Cold Plunging, Testosterone & Sexual Performance (For Both Men & Women!), With Dr. Thomas P Seager

My name is Ben Greenfield, and on this episode of the Boundless Life Podcast—

and you still see this nonsense on social media where people are like, ice baths don't work. If a man is doing his ice bath after his exercise to reduce delayed onset muscle soreness or something like that, it will suppress his testosterone. But if you reverse it, if a man does the ice bath before the exercise to pre-cool, it will boost the luteinizing hormone and it will boost the testosterone. We did 4 documented case studies and then we added women. It turns out women also get a big boost in testosterone. Most women don't know how beneficial that is for them.

Welcome to The Boundless Life with me, your host, Ben Greenfield. I'm a personal trainer, exercise physiologist, and nutritionist, and I'm passionate about helping you discover unparalleled levels of health, fitness, longevity, and beyond.

Ben Greenfield: A lot of people have a love-hate relationship with today's guest because he happens to be responsible for helping to make the coldest ice bath, as far as I know, that exists. The kind of ice bath where assuming you have it set low enough, you have to, like mine, break through the ice to actually get into your tub, which I love because it's just kind of primal and badass to have giant icicles poking you in the ribs as you're doing your ice bath. So, his bath is called the Morozko Forge. His name is Thomas Seager. And, Thomas is super cool. He's a PhD associate professor at the School of Sustainable Engineering at Arizona State University. So, he lives in Phoenix where especially this time of year, May-ish all the way up through I would say October, ice baths come in really handy. But perhaps even more interestingly, Thomas just finished this book. He sent it to me. It's called "Uncommon Testosterone: Cold Plunge Therapy for Optimizing Sexual Health." Who knew that one could write an entire book on the link between cold exposure and sex? But Thomas, you managed to pull it off, dude.

I'm glad to see that your book looks dog-eared and well-written in. I think you've been taking some notes.

Dude, I read the book. A lot of people, I don't know if you get this, but I get books sent to me by people or by publishers who want to have people on the podcast and they come with this 8.5 by 11 sheet. This is the dirty secret of podcasting, I guess. And, that sheet has all the questions that the author desires to have asked to them, a summary of the book, a quick bullet point GPT-esque summary, And, I know for a fact that a— not to throw anybody under the bus, but a large number of podcasters don't read the book, grab that 8.5 by 11, and literally read the questions off of that. And, my problem is I'm a nerd, I love to read, I've been a bookworm since I was 4. So, my books look like this. I read them all. I have no fancy Post-it note or colored sticky. Protocol so all my books are destroyed because I just fold over the pages. And not only that, but if you actually read the book, there's writing all over it. I write in the margins, I circle stuff, I say things like, "Thomas is an asshole.

This isn't true." It's not the first time I've heard that.

Yeah. So anyways, man, I think maybe people have heard you or heard of you before. Know that you are kind of like the ice bath guru. But what do you do as a professor? Like, what do you actually teach?

I teach engineering courses. I teach a class called Engineering Business Practices. I teach Quantitative Methods to Sustainable Engineering, and I teach systems engineering classes because I'm trained as an environmental engineer, and that's where I started my career.

Okay, so, so did the ice bath idea come about because you're good at like tinkering and engineering?

I build machines. The physicians, they work inside the body. The environmental engineer works outside the body. And so, I like to say a doctor can save one life, one patient at a time, but the environmental engineers, clean water, clean air, we work on the scale of millions of people at a time. So, I got the water chemistry, I got the toxicology, I got a lot of the good coursework from my doctoral training. But it wasn't really what I did for my career. After Katrina, I realized it wasn't about pollution so much. It was about disaster response. It was about resilience. That incident moved me towards this pathway of how do people recover from catastrophe. And then, of course, we had the COVID lockdowns, which were an even bigger catastrophe. And that's when I realized it's not in the concrete or in the steel. It is in the human creativity. That is where resilience lies. It is in our relationships. And, my whole career has been organized now around human resilience, well-being, and health.

Yeah. So, the cold plunge thing, was this a class project or was this scratching an itch that you had in some way?

No, this was because I was doing cold showers. I read in a book it would toughen me up.

I mean, if you live in Phoenix, it might not toughen you up. What do the cold showers get to there, like 60 degrees?

Like 60 degrees. It was pathetic. And I thought I was in there swearing and stuff. I thought that that was something, but it wasn't. It was just enough to piss me off. But then, I got a call from a former student of mine. You've met him, Jason Stauffer. And he said, "Well, you ever done an ice bath?" And I said, "No, have you ever heard of Wim Hof?" I said, "No, but I went to one of these Burning Man splinter groups and they're doing yoga breathing stuff and you get into the ice bath." I'm like, "All right, I'm open to it." It was fantastic because when you do the cold shower, you never get that dive reflex parasympathetic relaxation response. You only get the sympathetic activation. So, it's no wonder I was angry all the time. But then, you get into the ice bath, the dive reflex takes over 30, 45 seconds after you're submerged up to your neck in ice. Relaxing, calming, brainwaves slow down, heart rate slows down. I'm like, "This is terrific." So, Jason and I started doing it in his backyard every weekend except that got old, Ben, because back then, there was no such thing as a machine that would make ice in an ice bath. We had to go down to the Kwik-E-Mart and get the bags.

Ben Greenfield: I was there. I was there long before. Now, we're going to sound old, but before any ice bath I know of had ever been designed like a done-for-you, this was way back in my triathlon racing days. I knew nothing about the health aspects of cold. All I knew was, whatever, I've got a race coming up, it's in Tahoe, it's in 2 months, the water isn't cold enough in my local river, so I'm going to fill the tub with ice and do soaks each— like, for me, it was just purely performance and cold acclimation. Find out about the health benefits until later on. But yeah, it was like every time I'm out and about or my wife's out and about, "Can you get the big-ass bag of ice from the gas station because I'm filling up the bathtub again tonight?" And in Phoenix, it melts in 15 seconds.

I mean, you know I'm exaggerating, but it's 115 in the backyard. You put all this ice in there which is taking you 45 minutes to prepare and then a couple of guys get in and the whole thing is melted and you feel like, "Why did I even bother?" So we said, all right, we're engineers. We gotta make a machine that is gonna make its own ice. We started taking apart freezers and refrigerators and putting them back together and stuff. And we built one. That led us to have a party. Some people were like, hey, this is great. I wanna buy one. You know, the first Morozko we ever put up for sale, I think was on Etsy. And it was shortly, I shouldn't say shortly, it was months after that, that you found us and you called us up. I had no idea what digital marketing was or affiliate marketing. I didn't know who you were. I'm just a university professor. I'm like, who is this guy in, you know, Spokane where you were living at the time who wants an ice bath? And then you were kind enough to write us into your Boundless book because at the time there was no such thing. And you're like, hey, I know two people, Rick Rubin and these crazy Morozko people, right? And we're like, "That's so kind. We should send him an ice bath," which we did. And I remember you put it outside and you froze it solid. Like, first thing, it's 18 solid inches of ice. And I'm like, "Well, when is this Greenfield guy ever going to get into that thing?" You know, I was watching the weather report in Spokane. You know, I'm popping like the daily forecast. I'm like, "When is this thing going to melt and when is Greenfield going to get in it?" And it finally got up to like, I don't know, 38 or 40 degrees where you live. And then, you posted. And, that's when people are like, "Wait a minute, what? There's an ice bath that makes ice?" It catalyzed. I mean, Wim was doing great stuff popularizing cold plunge therapy, but when you posted from your morozko and people realized that they could have a machine in their backyard, it changed everything. You can look at all the analytics on ice bath searches and cold plunge. People got really curious.

Yeah, yeah. And, I think that is a differentiator. And actually, I had Jason up to my house. We did a great podcast and I'll link to that one if you go to BenGreenfieldLife.com/Uncommon like the name of Thomas's book, "Uncommon Cold," BenGreenfieldLife.com/Uncommon. Go check out that episode because in that one, we get into more of the engineering, the mechanics, how it stays so cold, everything. But, in the interest of time, I want to dedicate this show to a little bit more of this sex testosterone type of stuff that Thomas talks about and that he's figured out. And, I think in the book, if I remember, you said this started in terms of you looking into the sexual piece of it, Thomas, when you had some kind of— it was like a prostate issue or something that you were using cold bath for.

I did not get serious about ice baths until I got a lab report back with my prostate-specific antigen. So, this is a PSA. And, I was, I don't know, 52 at the time. It's very typical for men that age to get a PSA checked. Mine was 7. Anything above 4 is considered an elevated risk for prostate cancer. So, I got this lab test and I go straight to WebMD or whatever it was online. You spend 20 minutes online and you're going to convince yourself that you will die. Because that is what happened to me. You read about all the catastrophic things that could be associated with an elevated PSA. All the PSA measures is inflammation. But, when you think about what are the things you're supposed to do as a man who's in his early 50s who has a PSA like that, well, you get a prostate exam and of course, that's going to show some inflammation. So, then they say, "Well—" I guess nowadays they might do an MRI, but "Well, we should do a biopsy." They stick a needle into your prostate. They extract 16 tissue samples. It's very painful. Some of those are going to come up positive because the rate of false positive on a prostate biopsy is very high. So you get maybe 5 or 6 pop positive and you don't know if you have cancer or not. So then some surgeon says you should have your prostate removed and that signs you up for a lifetime of erectile dysfunction. So here I am. Looking at this lab report, talking to other men who've had terrible experiences. I'm at that time separated from my wife and I'm like, there's no way I'm not signing up for this because there is no woman who is ever going to love me if my penis doesn't work. I said, I'm going to do everything that I can do except go see the urologist. I went in and out of keto. I cycled in and out of a ketogenic diet. That's good for inflammation. If it is cancer, that's good for cancer. And I got into that dang ice bath. Every day because I was scared for my life. It took me 4 months before I had the courage to test again, 'cause you can imagine if that test comes back and the PSA is higher, I almost didn't wanna know. It came back 1.8. So what I was doing with the ice bath and the keto was working. And now I'm no longer at an elevated risk for prostate cancer. I tested again in another month, I came down to 1.1. And I said, at this point, I should go see the urologist, right? I won. I'm going to get a big pat on the back and he's going to say, you know, you're some kind of a genius, Professor Sieger. How can I change the way I treat my male patients? Is what I was imagining. It's not what happened at all. He took a look at my test report and I had gotten like the whole male health panel. It includes total testosterone. My total testosterone went from 700 to 1,180 nanograms per deciliter. An 1180 in a fat, you know, 52-year-old college professor.

You weren't on TRT or anything? Nothing.

Okay. But my urologist thought I was. He thought I had to be because he's about my age and he looked at me and he's like, "No freaking way." Now, most medical doctors believe that elevated testosterone will increase the risk of prostate cancer. They are dead wrong. That's not true. The data Right, 40 years of data disagrees with them, but they still teach this misconception. So, when he saw my elevated T, he's like, "I want to do one more test." He sent me back to the lab to measure luteinizing hormone. Luteinizing hormone, I found out later, is what signals the testes to produce testosterone. So, if my total T was high and my luteinizing hormone low, he would have chastised me severely and told me to get off the roids, you know?

Yeah, exactly. Because if you're on TRT, it will suppress LH and FSH. So a typical lab shows elevated total, often elevated free, and then low LH and FSH.

You got it. Except my LH came back 8.9, which was off the charts high. So yeah, he knew I was natural and I never heard from him again. Wow. Well, I had to write an article about it, you know, because once I saw, I didn't know why, but once I saw what was happening to me, Jason had to try it. He took himself up from mid-500s to mid-900s doing the same thing. And, the protocol is different than what most people think. Most people think you do your run or you do your workout and then you use your ice bath for recovery. And, you still see this nonsense on social media where people are like, "Ice baths don't work." If a man is doing his ice bath after his exercise to reduce delayed onset muscle soreness or something like that, it will suppress his testosterone. But if you reverse it, if a man does the ice bath before the exercise to pre-cool, it will boost the luteinizing hormone and it will boost the testosterone. So when Jason tried it and he got the same results, we thought, all right, we're really onto something. I put an article up at Morozko Forge. Nobody read it. Google was not sending people to my silly little article until Joe Rogan read it out. And, I remember that day very well because it was December 2022. I was in Iceland to see the Northern Lights. And, Joe Rogan read it to David Goggins. He said, "I'm trying this different thing. I read about this guy and his testosterone, you get a big boost." if you do the ice bath before your workout. Since then, Ben, I have heard from men all over the world. They are sending me their lab reports like, "This is where I was before. This is where I—" And then, I tried your protocol. "This is where I am after." And, with a few exceptions of men who have either been on TRT for a long time and their testes have atrophied or they're taking other medications that suppress testosterone, everybody is getting a big boost. So I put that right into the book. We did 4 documented case studies and then we added women. It turns out women also get a big boost in testosterone. Most women don't know how beneficial that is for them. They're afraid of becoming masculinized. They don't know, especially after menopause, that deficient testosterone contributes to menopausal symptoms, to low mood.

And also low bone density and loss of libido. Correct.

There are no FDA-approved protocols for treating women for low testosterone. So, if you're a clinician and you got a woman, you're like, "Well, she would really benefit from a little hormone replacement therapy here," you've got to take a male medication and adapt that protocol for the woman. Imagine now the breakthrough where a clinician could say, "I tell you what we want to do." Let's put you in the ice bath and let's measure you 3, 4 weeks later, and we'll see whether just stimulating your fat cells, skin cells, and adrenal glands will boost your testosterone. Because about 75% of the total testosterone in a woman's body, it comes from fat cells, skin cells, and adrenal glands. Only 25% comes from the ovaries. And after menopause, The ovaries just are nowhere near active. So, the rest of the tissues have to make up.

Synthesis in women of testosterone is like 3/4 non-gonadal. Correct.

Things we did not know until we got to go to the library and we really got to dig in to why are we observing these phenomena. We know what happens before and after, but we have to understand the mechanism by which it takes place or we don't really understand the phenomena. That's the problem with almost all the testosterone research. So, it typically says, "Well, we're going to take a bunch of guys and we're going to feed them Tongkat Ali or fenugreek or D-aspartic acid or boron or any of these things that are supplements." And, some of them do stimulate testosterone production, but none of these studies are hypothesizing how. They lack a mechanistic understanding.

That's what I wanted to ask you when you're talking about, well, if a guy does it and especially if he does it before his workout, he gets this increase in testosterone. And, what I'm wondering is, well, how do you know and is there any research behind that? And, even if not, what's the mechanism of action you're proposing? So, it sounds like you're about to explain.

There's some good research behind this and the mechanism makes all kinds of sense. Testosterone is synthesized in the mitochondria. Specifically at the inner membrane of the mitochondria. There's an enzyme there that will cleave a hydrocarbon chain off of cholesterol and form a sex hormone called pregnenolone. That pregnenolone is then metabolized into all the sex hormones, whether it's DHA or estradiol or testosterone. It's also the precursor to cortisol. So cortisol and testosterone come, they originate in the same location from the same cholesterol substrate. Now, if your mitochondria are defective, dysfunctional, or you just don't have enough of them—

Or maybe even avoiding the evil cholesterol, it might be another—

You could be on a statin. Yep. So, correct. You must have the right raw material to make the testosterone. And, there's some good research that shows the lowest quintile of cholesterol, so men in the lowest quintile also have low testosterone. It looks like after you get into that sort of average level, you have enough cholesterol. But, if you're on a statin or you're doing something to try and suppress your cholesterol levels, you will also suppress your testosterone levels. And, nobody is explaining this to men. Ben Greenfield: Yeah.

Okay. So, the mitochondria, that's where we see synthesis occur into pregnenolone. From this hydrocarbon cleavage that you're talking about. And so, based on that, what are you hypothesizing here or proposing is the mechanism of action in terms of how that relates to cold?

There are several things you can do to improve your mitochondrial function, and the best one is cold plunge therapy. Exercise will help. Magnesium supplements will help. Red light will help. You've done this experiment with yourself where you take your red light, you irradiate your nuts and you see a big boost in testosterone.

Ben Greenfield: I was in Austin a few months ago. I don't want to be crass. If you're in the minivan with the kids, earmuffs, please. But, I had my penis injected with stem cells, PRP, and of all things, Botox, which apparently relaxes smooth muscle tissue and allows for better blood flow. And, that's all great. It actually works fantastically, but as I'm walking out, the doctor gave me a red light— how do I call it? Red light sheath. So, I've gone beyond the balls and now just the whole package is getting red light.

Good on you.

How's that working? Fantastic.

When I discovered my elevated testosterone, I was going out with a woman who said, "Well, that explains a lot." She said, "Promise me that you will not do anything that might further elevate your T levels because I can't keep up." And, I've spoken with other men who experience a similar phenomenon in their relationships. Ben Greenfield: Yeah.

Well, I mean, yeah. I mean, I guess my wife and I just consider it our evening exercise protocol and we're happy with that. But anyway, so you're saying about the red light, allowing for, I think you were saying, better mitochondrial activity in the testes, which should increase testosterone. And, you're saying something similar happens with cold?

Correct. It's not just similar. I mean, it is analogous and it is so much better. The best way to stimulate what's called mitobiogenesis or the formation of new mitochondria is cold plunge. It's better than exercise. It's better than clean diet. It's better than the red light because the red light will stimulate the mitochondria you have, The cold plunge will stimulate the production of new mitochondria.

And, there's some good animal models and clinical studies. A drop in temperature of the testes or just of the body in general?

Body in general is what I'm advocating for because you know that non-shivering thermogenesis takes place in brown fat. What some people don't realize is that a body without brown fat can restore it. That is, new brown fat can be recruited to your body, even if you've lost all of your brown fat because you haven't been doing cold exposure. That new brown fat is packed with mitochondria. So, we're talking about thousands of these little mitochondria organelles so that they can fuel non-shivering thermogenesis. When you get into the cold, your body responds by revving up the mitochondria. The cold is stressful. But it's a hormetic stress. So, in your recovery from the cold, your body is saying, "We need new brown fat. We need new mitochondria. We got to get rid of the old defective ones," which is called mitophagy. And, the entire mitochondrial function elevates as a result of a regular practice of cold exposure. Keeping the testes cool is like an extra bonus.

Ben Greenfield: Now, for the men versus the women, I think you mentioned this in your book because it makes sense. I've experienced this firsthand. If anybody hasn't tried this, I also talk about this in my podcast with Brad Kearns. This idea of pre-cooling before workout is great. I mean, don't do it and then start your workout with some biomechanically complex move like a clean and jerk. I usually like to do the cold, ride the bike for a little while to warm up, and then go start the weights. And, it just works. Don't knock it till you've tried it. If you're sluggish to start a workout, you do this, you're on top of the world. I just did it this morning. I posted to Instagram, I tagged you, Thomas, 33 degrees, minute and a half, then headed into the gym. So, for women though, I think you said it was different in terms of when a woman does the cold plunge versus the man. Am I remembering correctly?

Women don't need the exercise. They get an immediate testosterone boost. Now, in the man, the adrenal glands, the skin cells, the fat cells will also produce testosterone. But men have so much greater need for testosterone than women, and the testes have to do the heavy lifting in the man. When you plunge the man into the cold, the cold temperature is great for testes, but not 33-degree Fahrenheit cold water. The man must get out, he must restore his circulation to his limbs, he must do some rewarming, and then he will experience the testosterone boost. Women, not the case. When women get in, all of these secondary testosterone-producing organs, they kick into gear right away. You know this because I have seen women in the ice bath. I've experienced this with them where they get in and they're in a certain mood and it takes maybe a minute before they start smiling and giggling. And at 2.5 minutes, when I've done this with my partner, she gets randy, for lack of a better term. I went in, I was having the biggest argument with this woman that I was dating, and we didn't even want to look each other in the eye, but we were doing a photo shoot. And so we have this on film. After 2.5 minutes in the ice bath, Ben, we are making out., and I don't know what's going on, but she's like kissing me and the videographer is like, "Cut, you two get a room." We fell back in love. And, it was because the neurotransmitters and hormones inside her body had erased all the animosity and resentment that was part of the argument we were having at the time.

You're almost replicating what, I don't know, a glass of wine or two with your partner might do.

It's better than that because the glass of wine does not create oxytocin. It does not create dopamine. It might release inhibitions, but it doesn't create testosterone. And, we know testosterone is the lust hormone. So, all of these neurotransmitters and hormones that the ice bath stimulates are directed sort of that feeling of affection and attachment is directed to the partner that you're doing with it.

Ben Greenfield: Yeah. And obviously, oxytocin, by the way, that's an attachment-related hormone. You seen any data on oxytocin and cryotherapy or body temperature?

Yep, there's good stuff. There's like 250 scientific citations in the Uncommon Testosterone book, and several of them relate to oxytocin levels in response to cold plunge therapy. Vasopressin is similar. Vasopressin is also a bonding hormone, and you might be familiar with vasoconstriction and vasopressin. They sound similar because vasopressin is the hormone that signals the vasoconstriction. That is, you don't get vasoconstriction without elevated vasopressin. Vasopressin also has these sort of relational qualities. It creates bonding between a couple.

Okay. I do have an adult question based on your partner cold plunging tip. There's obviously, especially based on the vasopressin vasoconstriction, some amount of potential lack of blood flow to penile tissue do you do anything about that? Is that a problem? Guys get worried about shrinkage. Some guys even think that maybe it'd have an effect on erectile dysfunction, cold plunging, because of the vasoconstriction. How do you tackle that whole piece?

So, there's two aspects to this. One is my experience has been that an ice bath is no barrier to an erection. And, under certain circumstances when I'm with the right partner with whom I'm attracted and other men have reported to me similar things, but the second one is more important. Erectile dysfunction is the first clinical marker of insulin resistance. If you're not getting enough blood flow to your penis, it's because the endothelial cells that control vasodilation are not functioning properly. It used to be that medical doctors thought mitochondria were not important to endothelial function. And that's because when they were measuring the metabolism of these endothelial cells in the lab, they didn't notice mitochondria active, but they were only measuring it during proliferation of the endothelial cells. So division in the test tube. When the endothelial cells are signaling or creating the nitric oxide necessary for vasodilation, they are using mitochondria to produce the ATP that fuels the nitric oxide production. And this is research just from like 2, 3 years ago. Your mitochondria, when they're defective, your endothelial cells will not produce sufficient ATP. You don't get the nitric oxide, you don't get the vasodilation, and that's why erectile dysfunction is the first sign of metabolic dysfunction. So what are you going to do about it? You get into the cold plunge, you stimulate the mitobiogenesis, You take care of your mitochondria, your endothelial cells will take care of your penis.

So, you don't have any issues getting it up after a cold plunge?

I don't have any issues getting it up during a cold plunge. There's no issues.

I have to admit I'm asking because that is, and I'm pretty healthy, but that is a problem. I've never been able to get an erection after a cold plunge without warming up a little bit prior. And, my wife and I have had dates where we'll do sauna and cold plunge and with a cold plunge. Too much information for some people, but head up to the bedroom. And, I'll admit it takes longer than usual to warm up.

I have had a girlfriend whom I was with for a while and her only complaint was that I felt too cold. My skin was cold. Now, here I am feeling like we're in there, we're going in naked. I'm like, "Oh, this is great." She's feeling affectionate. And I want to go right at it. But, some aspect of rewarming was important to her. It wasn't the physiological limitation that I was experiencing, it was a certain comfort level with my skin temperature that she was experiencing. That was the only thing that would slow us up.

Ben Greenfield: Yeah, interesting. Okay. Well, different strokes for different folks, pun intended. So, if there's this type of influence on testosterone, potentially even libido, blood flow. What about fertility? I've heard anecdotally that some people have not been able to have a baby and then one thing that they changed was cold plunging and all of a sudden, lo and behold, the stick marks positive on the pee test. What have you seen as far as fertility goes?

Let's talk about men first because it's easy. Most men understand that heat is not good for sperm production or sperm motility. And so, if you're trying to conceive, stay out of the sauna.

Yeah. Have you seen those underwear? They call them snowballs or something like that. They apparently keep the scrotal tissue cool when you're in the sauna.

I don't know if they do or don't, but it's in the popular understanding. The more interesting case, of course, is the women. The leading cause of infertility among women of childbearing age is called PCOS, or polycystic ovarian syndrome, and PCOS is strongly associated with metabolic dysfunction. The most demanding thing that a woman can do is pregnancy, and during pregnancy, there's a lot of growth hormone coursing through the woman's body. That growth hormone interferes with the action of insulin. Now, ordinarily, this isn't pathological. I mean, this is just normal. So the— your pancreas or her pancreas will make a little extra insulin, maintain healthy blood glucose. But so many women, by the time they hit their mid-30s, are already suffering from some degree of mitochondrial impairment that their fertility falls down off a cliff. It's not because they're old. There's this term geriatric pregnancy. I object. It suggests all the wrong things about the woman's body. It's not because of age. It's because of the state of their mitochondria. When you target the mitochondria with therapies, uh, this might be the ketogenic diet, it could be cold plunge, it could be other things that restore mitochondria, like getting rid of all the seed oils. There are so many surprise bonus babies that will show up in the practice of an OB-GYN who's targeting mitochondria as the therapy for fertility. There are women 40, 42 still conceiving and having a healthy birth outcome because they've restored their metabolic function. Some of them are afraid to cold plunge during their pregnancy because, you know, if you're already 38 and you're so grateful to have the baby and you're so looking forward to it, of course, you're risk-averse. But, But every woman that I've spoken with, we have some good case studies, has terrific outcomes as a result of cold plunging during pregnancy.

I would imagine that vagal nerve function does not do any disservices to making pregnancy a little— or childbirth a little easier also.

There's a great paper on that, and I think it's Gunderson and Atkinson are the authors, but you can't quote me. They talk about the way the cold plunge improves stress management in the woman. Reduces inflammation, for example, in the ankles. And here's the critical one, improves insulin sensitivity at a time when she's becoming more and more insulin resistant. So this is especially in late-stage pregnancy. Several of the common maladies that are associated with poor birth outcomes or premature birth, preeclampsia, gestational diabetes, placental insufficiency, they're all associated with poor metabolic function. And cold plunge will help the woman manage that. Conversely, heat is very bad during pregnancy. There's good epidemiological data on this as well. Women in colder climates have better birth outcomes than women who experience heat waves. So, a woman, a pregnant woman's got to stay out of the sauna, but the cold plunge is good.

Yeah, yeah. And then, I mean, if you're really badass, you know, there's this whole home water birth phenomenon I don't know if anybody's done it yet, but water birth in a marasco.

The home water birth, never mind about home birth, water birthing in general is a wonderful thing. When my son was born, my wife labored in the water for as long as she could. Her OB-GYN didn't want her in there after her water broke, which is fine. But when you think about our ancient grandmothers, like, how would they give birth? It's nothing like what our wives are doing now. They don't go to the maternity ward and lay on their back. They likely went into the water. We don't want any interventions to be standard operating procedure during childbirth because that's not a disease. That's not a sickness that requires intervention. Now, there are abnormalities, and there's a lot of things that can happen, and thank goodness we have medical procedures to deal with them. But, standard interventions are associated with higher rates of infant mortality and poorer birth outcomes. Ben Greenfield: Yeah, I agree.

I interviewed Marty Makary about this a few months ago. I'll link to it in the shownotes. Just, a real eye-opener on how far we've strayed from elements of natural childbirth that frankly could still be woven into a modern medical system where we can take advantage of the opportunity to prevent mother or child death in a pregnancy scenario. We started with water birth and eventually after 10 hours wound up at the hospital. I'm very glad the hospital was there to help my little petite wife give birth to twin boys that her pelvis was just not going to let out. And so, we opted for C-section. But, other things in the hospital like them being removed immediately, placed under lights, given the injections, taken away from mom, those are things that I think are largely unnecessary. Don't wash that baby.

Put that baby right on mom's chest or in my case, it was dad's chest because my wife tore, she needed a minute to get stitched up and it was fine, but that baby needs the heartbeat. Marty, I'm so glad you brought up Marty because before he was appointed to direct the FDA, he published this book called Blind Spots. He gets it. Yeah. When you think about the way that our ancient grandmothers gave birth, I'm convinced it was in the water. Because human babies are born with an instinct to swim. When they come out, they are capable, of course, of holding their breath, but they also make swimming motions with their limbs. Now, if you're a giraffe, you're born with an instinct to, I don't know, prance around or something. But a human baby doesn't know how to walk. It knows how to swim when it's born. I think that indicates that our ancient grandmothers or mothers gave birth in the water.

Yeah, yeah, exactly. And maybe we're just evolving on this water planet and eventually will be born with webbed fingers and toes. Who knows? And I'm joking, by the way, for those of you who know, I'm one of those 6 days creation guys. But anyways, on to some other considerations. There is obvious resistance to some people to cold bath. I think honestly until you get used to it, even the friction of stopping on your way into the gym and jumping in cold cold water can sometimes be a stopper for some people. I'd rather people get in and do the workout and not have the cold bath actually stop them. Although, as Thomas noted, once you're in there 30 seconds, parasympathetic drive takes over and you're good. You just have to get in there first to realize and feel that that happens. And, a lot of people don't give it even more than 15 seconds before they're like, "Screw this, I'm out." But, one thing that I'm often asked about is Raynaud's. My hands get cold, my feet get cold. Thomas, my take on this is that in anybody who I've convinced to do it consistently, after about 2 weeks, the hands and the feet stop getting cold. And I think, it's not based on research, that it's a potential cure for Raynaud's. Give me your thoughts on Raynaud's and cold plunging.

Case studies agree with you. I have 3 case studies, one that I experienced directly and 2 that have been reported to me by others. Of women who have resolved the Raynaud's syndrome with cold plunge therapy. There's something called stress exposure. Sometimes it's called stress inoculation, but this exposure therapy, you know, say you're afraid of spiders. Well, first you just look at magazine articles of spiders, and then maybe you're in a room with a spider that's in a terrarium or something like that. You titrate exposure to the stress until the person becomes acclimated. Renals is not just a physiological phenomenon, it's a feedback loop between the psychological and the physiological, which is why some people will experience an extreme vasoconstriction response even if it's only like 60 degrees out. To overcome it, you can titrate exposure to the cold in a safe environment where you're supported by a coach or a guide and gradually work your way down to colder temperatures. The woman that I'm most familiar with, she didn't want to do cold plunge at all. She experienced— she'd been living in Arizona for a while, probably had no brown fat. She experienced acute Raynaud's attacks. They were very painful, but she saw her daughter who has cerebral palsy go into the cold plunge. Her daughter doesn't have the same sensations from the waist down that she has. And, the daughter's like, "Mom, this feels really good. Can I go in up to my armpits?" Mom, this feels really good. How long have I been in? 4 minutes, 5 minutes. The little girl's 9 years old. She looks up at her mom and she says, when are you going to go in, Mom? Mom is on the verge of tears because she can't imagine herself going in, but now she feels like she has to. So she asked me, how are we going to do this? I want to go in for my daughter. And we started at a warmer temperature. It wasn't 33 degrees. We did the breathing. We talked her through it. Next thing you know, she's at 34 degrees, fully immersed up to her neck, hands in the water, no Raynaud's anywhere. And, that was about her third ice bath. So, you step towards it, but when you have a psychological purpose and you feel like you have the safe and supportive mentor or guide that you need, you can overcome Raynaud's using exposure therapy. Most people get advice from their doctors that says, "Oh, you should stay warm. You should keep the thermostat higher." Ben Greenfield: Yeah.

Okay. Another topic. You say magnesium is critical. You mentioned magnesium earlier, and you mentioned it, by the way, in the context of mitochondria, but I don't think what I'm about to ask you is in the context of mitochondria. You said magnesium is critical as a supplement if you're going to be doing cold bathing. I'd never heard that before.

Why do you say that? Magnesium catalyzes hundreds of metabolic reactions. Magnesium is essential to mitochondrial function, so it does attach to the mitochondria. The funny thing about magnesium is almost none of it is stored in your blood. Only 1% of the total body burden of magnesium is in the blood. Most of it is in the bones. It can also be in the muscles. But when you get cold, blood serum studies show elevated concentrations of magnesium in the blood. Here's what I think is going on. It is released from the bones into the bloodstream so it can reach the brown fat, so that it can reach the muscles to fuel this non-shivering thermogenesis. If you are practicing cold plunge every day and you do not supplement with magnesium, you can deplete your bones of the magnesium because your body will preferentially reallocate it to the mitochondria. Eventually it will be peed out. Magnesium doesn't stay in your body forever. And so that supplement is essential to avoid problems with bone metabolism because you're using up the magnesium that would otherwise be stored. And this explains the epidemiological data from people who have long-term chronic cold exposure and then find that that's associated with osteoporosis or other bone abnormalities. I got it.

That makes sense. And you could probably just like take your magnesium in the evening before bed as you normally do. It's not, it's not like you got to take it right before you get in the cold plunge. Correct.

Although, I put all kinds of Epsom salt into my Morozko and then I don't shower afterwards.

You don't have an issue in the Morozko with the filtration or anything like that with putting the Epsom salts in?

No. Sulfate salts, no. Chloride salt, leave them out because we don't want any interaction between the chloride and the ozone. But, you can put in yours magnesium sulfate, potassium sulfate, copper sulfate, Zinc is a really good one to add to your morosco.

Ben Greenfield: Okay, cool. Yeah, I got a bunch of bags of Epsom salts. I just haven't put them in there yet. I'll do it. Okay. So, I have heard, as a matter of fact, many times even this year that cold plunging is so stressful. You're running from a lion. It's the same as getting chased by a bear or eaten by a shark. Avoid it. It's going to cause you to go into adrenal fatigue because of the hypercortisol surge and the eventual adrenal exhaustion. I doubt you'd deny that there's a cortisol release when you get into the cold plunge, Thomas, but what do you say to the people who are saying, "Dude, this is way too stressful?" I say they're getting a lot of great clicks.

I see those accounts. I put up something on cortisol and I got my scientific citations, I might get 75 likes. Then, one of these other accounts puts something out, they get 75,000 talking about a thing that doesn't even exist.

There's probably 75 people who like cold plunging and 75,000 people who don't. So, exactly. How that works out.

There are 3 ways to think about cortisol. The first way is lots of laboratory studies where they administer exogenous cortisol to a human or an animal model and they say, "Oh, look at what happens in the body when we spike it with cortisol." Throw all that stuff out. That doesn't matter because endogenous cortisol is different than exogenous cortisol. So, here's the other two ways. The first one is short-term. We brought in a bunch of research subjects, we put them in a cold plunge one time, we took some blood samples, we measured saliva, and we got a cortisol spike. That can be a good thing. For example, people with PTSD, they have chronically low cortisol typically, Not everybody, but when you have PTSD and your cortisol is chronically low, it turns out that you don't benefit from talk therapy or other trauma-related therapies. There's a clinical trial in which they raised the cortisol levels prior to these other conventional therapies, and the people with PTSD responded quicker. If you have low cortisol, getting your cortisol higher is a good thing for you. The other thing in the short-term study is that if you already have high cortisol, the best work so far is coming out of the Lithuanian Sports University. There's a woman there, Rima Solejanić. She's a friend. She came to visit me at ASU, and she saw that those with high cortisol do not spike any further in a one-time study. So cortisol levels that are low coming up is good. Cortisol levels that are high are not going to go any higher. But the third way to think about cortisol is over a longer term, say 2 weeks. And in the clinical trials where they've taken people and acclimated to them, to the cold over a period of 2 weeks, they notice a blunted cortisol response. That is, the more used to you get it as you cold train, you get less of a cortisol response. So these sensational social media posts that make up terms that sound medical but are not, like adrenal fatigue, they give people a good excuse to not do what they don't want to do anyway.

I actually want to see them trying it before they knock it.

Ben, you're so right. Show me your lab reports. Like, I posted mine. And when I do a video and I'm up to my neck in chunks of ice talking about the benefits of cold plunge, you don't have to worry that I'm not eating my own cooking. You know, you can't overdo it.

Like, I do know some people and all they watch is, I don't know, the TikToks or whatever where people are going 10 minutes. I haven't said this in the video I did this morning. 33 degrees for me, pre-workout, 60 to 90 seconds. And, if I'm going there as part of a sauna back and forth hot-cold contrast, it's 2 to 3 minutes. I can't tell you the last time I was in a cold bath more than 5 minutes. Why would you be?

2 to 4 minutes, that's what I do. And, I keep mine at the same temperature that you do. And, after 3 or 4 minutes, sometimes I get bored But that's not the point. The point is I'm done. I've got the benefit that I need. You and I are a little bit different because we've been doing this for years. If someone is just starting out, I get this question a lot. What's the optimal temperature? What's the optimal time? There is no optimal time and temperature because it depends upon your prior state of cold training. Just like weightlifting. You know, if I was going to start the bench press, you wouldn't say, oh, here's the perfect weight. Here's the perfect number of reps. You would assess my current state of training. Go cold enough to gasp, long enough to shiver. If you're just starting out a cold practice and you feel that gasp reflex, temperature is fine. You stay in there, doesn't matter, a minute, 5 minutes, and you feel the shiver, then you know you've activated that brown fat if you have any, you know you've started thermogenesis, you've got all the benefit, get out.

Spot on. I have a client, Brian. Hi, Brian. He listens to the show. And, he sent me a message the other day, he's like, "Dude, I'll do my cold plunge," I think he said like 8:00 a.m. "I'm still shivering at 10:00 a.m." I told him, "Look, dude, you have gone beyond the benefits. More is not better. Just cut it." I think he was going 5. I said, "Cut it down to 2 or 3 at the most. You don't have to be shivering uncontrollably for hours after you get out." Well, yeah, maybe if your number one goal is calorie burning, you might, but it's not worth the added stress to be burning a bunch of extra calories shivering your ass off for 2 hours.

You're giving them good advice. When it comes to calories, it's counterintuitive. You've probably seen some of the videos where it's like, "Oh, cold plunge is the best way to burn calories." And, if you have a continuous ketone monitor, you will see those ketones spike when you get into the cold plunge.

And, blood glucose goes down.

Correct. You are clearing glucose from the bloodstream. The liver will release glycogen stores. They are rapidly depleted. And so the white fat cells in your body will release free fatty acids to fuel that cold thermogenesis in your brown fat. And that's what causes the immediate ketone spike. And this is wonderful, especially if you're trying to get into ketosis or build metabolic flexibility. But then there's a phenomenon at night. Where compensatory metabolic mechanisms kick in. Your body temperature drops, and it drops more than normal.

Now, this is wonderful for sleep.

So, cold plunge can promote good deep sleep. But, what your body is doing by dropping that temperature just another degree and a half is it's trying to slow down the metabolism to make up for everything you did during the day and rebuild the subcutaneous fat stores. When you think about it, you know, is your body really going to get all cut because you're getting into the cold? If it did, I'd be ripped instead of like a fat guy because I've been doing this for years. We have subcutaneous fat just like dolphins or manatee or whales or seals. Chimps don't have that. Gorillas don't have it. Other primates with whom, you know, we're closely related if you just look at the DNA, aren't built like that. And, we know that in aquatic mammals, that subcutaneous fat helps insulate the vital organs from the core. So, this is one of the biggest misconceptions. If I were willing to go on Instagram and say, "Mirasco is going to help you lose weight," I'd probably sell 5 times as many machines, but I can't say that because you'll lose maybe 5, 10 pounds. You'll take the inflammation down. You'll remodel your fat. Your metabolism will get better, But, it's no miracle for weight loss. You're really not going to burn too many more calories.

Ben Greenfield: Yeah. And maybe, let's say the 180 extra calories you might burn by uncomfortably shivering your ass off for 2 hours in the morning is basically offset by the level to which your metabolism downregulates and goes into hibernation mode at night due to that cold exposure. So, I'm one of those embrace discomfort guys, but that's not, I think, great discomfort to embrace, especially if you're fooling yourself and think it's going to burn massive amounts of calories. Now, the other thing to bring up in this context, and I don't know if you saw this, the most recent study was maybe 4 weeks ago. It was the third such study I've seen that similar to many exercise scenarios, there is a hypercompensatory caloric consumption that occurs after cold. And, I say this because I do want people, especially people who might be doing it for some of the weight loss and metabolic components to know to check themselves, especially if they first start cold plunging, log your diet, something like that because you tend to without even realizing it almost subconsciously eat anywhere from 200 to 500 extra calories in whatever post-meal feeding occurs after cold plunging. And, this is something I've seen in studies. So, you do need to be aware of that. One of the ways that your body wants to warm itself up is by eating, and it's important to understand that and not just keep a bunch of extra calories on your plate and expect to lose weight or get as many metabolic benefits from cold plunging. And, I do think that with long-term exposure, the ketones that you get better and better at churning out kind of help to mitigate that anyways.

I had an experience Thanksgiving. You know, pumpkin pie is my downfall because I love pumpkin pie. And when it's leftovers, you know, it's the next day and you're not sitting down. You don't have the ritual. Thanks. I'm just like going through the fridge and the pumpkin pie is the first thing I ate, a whole dang half a pumpkin pie the day after Thanksgiving. And then I regretted it because, you know, that's not metabolically good for me. So, I peed on a stick. I measured my ketones. I don't have any. And I said, "I'm going to get in that ice bath." And it's just like 4 minutes. Came out a couple hours later, peed on a stick, ketones. I was able to clear the glucose from my bloodstream. And by the way, pumpkin pie, it isn't the worst. I got fiber in there and I don't make mine too sweet.

This last Thanksgiving, I got up, I took half the pumpkin pie and I made myself a pumpkin pie smoothie for breakfast. And it was amazing. The whole thing just went in the blender.

So good. That's great. Next Thanksgiving.

That's good. So good. You're right though, any big feast today, I cold plunge because of its effects on insulin sensitivity. And, even a big date night with my wife where we're going out to a place that might serve, I don't know, great sweet potato fries or sourdough bread or there's going to be a little bit more carbs on board, I cold plunge. It's like the secret weapon.

Exactly right. When you were saying if you overdo it with the cold plunge, you are going to stimulate appetite. And even unconsciously, you're going to increase the amount you eat. What also works is flip it around. If you find that you've overeaten and you enjoy it because it's great, you'd be like, "You know what? A couple of things I can do, cold plunge, go for a walk." and I won't experience the same blood sugar spike, this postprandial blood sugar spike as a result of overeating.

Yep. It's a little bit more ballsy than a walk, but I think more effective. Thomas, this book is great, "Uncommon Testosterone: Cold Plunge Therapy for Optimizing Sexual Health." You guys, we barely scratched the surface of everything that's in this book. I highly recommend it. I'll link to it in the shownotes. At BenGreenfieldLife.com/Uncommon. I'll also link to the Morozko. I think I have a special code that saves you $350 on a Morozko if you want the Cadillac of cold tubs for yourself.

Thomas, thank you, dude. This has been a pleasure. I'm so glad you like the book. I had you in mind. And, I'm in it. I'm in it. There's a page.

You are? I forget what I talk. What did I put in there?

Cold plunge is Viagra for the whole body. I've lifted that quote and said Ben Greenfield is right.

Alright, you guys, thanks for listening in. Again, the shownotes are at BenGreenfieldLife.com/Uncommon. I'm Ben Greenfield along with Dr. Thomas Seager of Morozko Forge signing out from BenGreenfieldLife.com. Have an incredible week.

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