The social media consensus on cold plunges and testosterone is incomplete and sometimes wrong. Dr. Thomas Seager, speaking with Ben Greenfield, is specific about what the evidence shows — and the nuance matters, because the direction of the effect depends entirely on when you plunge relative to when you train.
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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 precool, it will boost the luteinizing hormone and it will boost the testosterone. We did four 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. [Applause] [Applause] A lot of people have a lovehate relationship with today's guest because he happens to be responsible for helping to make the coldest ice bath as far as I know uh that exists. like the kind of ice bath where uh 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 uh you know poking you in the ribs as you're doing your ice bath. Uh so so his bath is called the Morazzco Forge. His name is Thomas Seager. And Thomas is super cool. He's a PhD uh associate professor at the school of sustainable engineering at Arizona State University. So, he lives in Phoenix where especially this time of year uh Mayish all the way up through I would say October ice baths come in really handy. Um 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 uh Thomas, you managed to
and sex? But uh Thomas, you managed to pull it off, dude. I'm I'm glad to see that your book looks dogeared and well written in. I think you've been taking some notes, dude. I read the book like a lot of people um I 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 like this 8 1 / 2 by 11 sheet. This is like 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 like a quick bullet point GPT summary. And I know for a fact that a not to throw everybody under the bus, but a large number of podcasters don't read the book. Grab that 8 1 / 2 by 11 and literally read the questions off of that. Um, and my problem is I'm a nerd. I love to read. I've been a bookworm since I was like four. So, my books look like this, right? I read them all. I have no fancy post-it note or like colored sticky protocol. Also, all my books are destroyed uh because I just fold over the pages. And not only that, but if you actually read the book, there's like writing all over it. I write in the margins. I circle stuff. I say things like, you know, Thomas is an [__] This isn't true. You know, it's just everything. It's not the first time I've heard that. So, um so anyways, man. Um, you know, I I think maybe people who have heard you or heard of you before know that you are kind of like the ice bath guru. Um, 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 a quantitative methods to sustainable engineering and I teach a systems engineering classes because I'm trained as an environmental engineer and that's where I started my career. Okay. So did the ice bath idea come about because you're good at like tinkering and engineering? I build machines. You
and engineering? I build machines. You know, 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, you know, 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 like a class project or was this like 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 °. Like 60 degrees. It was pathetic. And and I thought, you know, I was in there swearing and stuff. Like I thought that that was something. Um, 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 Staler. And he said, "Well, you've ever done an ice bath?" And I said, "No. Have you ever heard of him?" 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."was fantastic because when you do the cold shower, you never get
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 know, you're submerged up to your neck in ice. Relaxing, calming, brain waves 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 Quickie Mart, you know, and get the bags. And I was there. I was there long, 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 two 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 acclamation. I I didn't even 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 cuz I'm filling up the bathtub again tonight. And in Phoenix, it melts in like 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 got to make a machine that is going to 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 want to buy one." You know, the first Mirage Co we ever put up for sale, I think, was on Etsy. And it was shortly, I shouldn't
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 bat? And then you were kind enough to write us into your Boundless book because at the time there was no such thing. You're like, "Hey, I know two people, Rick Rubin and these crazy Morasco 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 ° where you live. And then you posted and that's when people were like, "Wait a minute. What? There's an ice bath that makes ice? It catalyzed. I mean, Vim was doing great stuff popularizing cold plunge therapy, but when you posted from your Morasco 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. And, you know, I I think that is the differentiator. And actually, I had Jason up to my house. We we did a great podcast and I'll link to that one. Uh, if you go to bengrenfieldlife. com, like the name of Thomas's book, Uncommon Cold, bengrifffieldlife. com, go check out that episode because in that one, we get into more of like 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 like sex, testosterone type of stuff that Thomas
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 of you looking into the sexual piece of it, Thomas, when you had some kind of like a it was like a prostate issue or something that that you were using the 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 uh I don't know 52 at the time. It's very typical for men that age to get a PSA checked. Mine was seven. Anything above four is considered an elevated risk for prostate cancer. So, I got this lab test and you know, 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 cuz 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, you and 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 five or six 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
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 four months before I had the courage to test again because you can imagine if that test comes back and the PSA is higher, I I almost didn't want to 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 Seager. 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 pale health panel. It includes total testosterone. My total testosterone went from 700 to 1180 nanogs per deciliter and 1180 in a fat, you know, 52year-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. The data, right? 40 years of data disagrees with him. But they still teach this misconception. So when he saw my elevated tea, he's like, I want to do one more test. He sent me back to the lab to measure luteinizing hormone. I found out later, is what signals the testes to produce testosterone. So, if my total tea was high and my luteinizing hormone low, he would have chastised me severely and told me to get off the roids, you know.
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. Fantastic. 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. Uh he took himself up from mid 500s to mid 900s doing the same thing. And the protocol is different than what most people think. you know, 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 precool, 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 on to something." I put an article up at Morasco Forge, nobody read it. Like, you know, 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 20, 2022. I was in Iceland to see the Northern Lights and Joe Rogan read it to David Gogggins. He says, "I'm trying this different thing. You know, 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, you know, and I charge you a protocol. This is
and I charge you a 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 four 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 masculineized. 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 testosterone is like three / arters non gonatal. Correct. things we did not know until you know we got to go to the library and we really got to dig in to why are we observing these phenomena like we know what happens before and after but we have to understand the mechanism by which it takes place or we don't really
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 uh well we're going to take a bunch of guys and we're going to feed them tongot alley or fenugreek or daspartic 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. You know, when you're talking about, well, if a guy does it, especially if he does it before his workout, he gets this increase in testosterone, you know, and what I'm wondering is, well, how do you know? And is there any research behind that? and and even if not, what's the mechanism of action you're proposing? So, it sounds like you're 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 been avoiding the evil cholesterol, it might be another another be on a statin. Yep. You 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
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. Yeah. Okay. So the mitochondria, that's that's where we see synthesis occur uh into pregnentoolone uh from this hydrocarbon cleavage that you're talking about. And so based on that, what are you hypothesizing here or proposing as 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. Uh magnesium supplements will help. Red light will help. You've done this experiment with yourself where you take your red light, you irdiate your nuts, and you see a big boost in testosterone. I was in Austin a few months ago. Uh I don't want to be crass. If you're in the minivan with the kids, ear muffs, 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 that's all great, and it actually works fantastically. But as I'm walking out, the uh doctor gave me a a red light uh how do I call it? Red light sheath. So uh so I've gone beyond the balls and now now just the whole package is getting red light. Uh good on you. How's that working? Uh fantastic. When I dis 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 tea levels cuz I can't keep up." And I've spoken with other men who experience a similar phenomenon in their relationships. Yeah. Well, I mean, yeah. I mean, I uh I guess my wife and I just considered our evening exercise
considered our evening exercise protocol. Uh we're happy with that. But anyway, so so you're saying about about the red light allowing for I think you were saying better mitochondrial activity in the testes which would increase testosterone and you're saying something similar happens with cold. Correct. It's not just similar um 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 mitochondrial organels 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 mofasagi. 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. Now, for for the men versus the women, I think you mentioned this in your book
think you mentioned this in your book because it makes sense, and I've experienced this firsthand. If anybody hasn't tried this, and I I also talked about this in my podcast with Brad Karns, this idea of pre-cooling before a workout is great. I mean, don't do it and then start your workout with some biomechanically complex move like a clean and jerk. Uh, I usually like to do the cold, ride the bike for a little while to warm up, and then go start the weights. Uh, but and and it just works. Like don't knock it until 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 ° minute and a half then headed into the gym. So for women though, I think you said it was different like 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 temperatures, but not 33 ° 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. The 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 two and a half minutes when I've done this with my partner she gets Randy for lack of a better term. I went in, I was
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 two and a half minutes in the ice bath bin, 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, you know, part of the argument we were having at the time. You're almost replicating what like, I don't know, a glass of wine or two with your partner might do. It's better than that. Um, because the glass of wine does not create oxytocin. It does not create dopamine. It does not 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 that feeling of affection and attachment is directed to the partner that you're doing with it. Yeah. And obviously oxytocin by the way that's an attachment related hormone. You see any data on oxytocin and cryotherapy or or body temperature? Yep. Um 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. Vasop prein is similar. Vasopressin is also a bonding hormone and you might be familiar with vasoc constriction and vasop prein. They sound similar because vasop prein is the hormone that signals the vasoc constriction. that is you don't get vasoc constriction without elevated vasop prein 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 uh there's obviously especially based on the vasopressin vasoc constriction some amount of
vasoc constriction some amount of potential lack of blood flow to penile tissue uh do you do anything about that uh Is is that a problem? Guys get worried about shrinkage. They get some some guys even think that maybe it'd have an effect on erectile dysfunction, cold plunging because the vaso constriction. How do you tackle that whole piece? So there's two aspects to this. Um one is my experience has been that an ice bath is no barrier to an erection. um 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 is because the endothelial cells that control vasoddilation 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 um creating the nitric oxide necessary for vasoddilation, they are using mitochondria to produce the ATP that fuels the nitric oxide production. And this is research just from like 2 three years ago. Your mitochondria 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 vasoddilation 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
will take care of your penis. So you don't have any issues getting it up after a cold punch? I don't have any issues getting it up during a cold plunge. Like there's just there's no issues. I have to admit I'm asking because that that is and and I'm pretty healthy, but that is a problem. Like I've never been able to get an erection after a cold plunge without warming up a little bit prior. And and my wife and I have had dates where we'll do like sauna and cold plunge and with a cold plunge and too much information for some people, but head up to the bedroom and I'll admit it takes longer than usual to to warm up. I have had um a girlfriend whom I was with for a while and uh her only complaint was that I felt too cold. You know, 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. Yeah. Interesting. Okay. Well, different strokes for different folks, pun intended. Um, so if there's this type of influence on testosterone, potentially even libido, uh, blood flow, what about fertility? like, you know, I I uh I've heard anecdotally that some people have like 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, you know, the the uh the the stick marks positive on the P test. Um what uh what have you seen as far as fertility goes? Let's talk about men first because it's easy. Uh, 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 like 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
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 mid30s are already suffering from some degree of mitochondrial impairment that their fertility falls down off a cliff. It's not because they're old. This term geriatric pregnancy, I object, it suggests all the wrong things about the woman's body. It's not because of their 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 OBGYn who's targeting mic 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 every woman that I've spoken with, we have some good case studies,
with, we have some good case studies, has terrific outcomes as a result of cold plunging during pregnancy. I would imagine that veagal nerve function does not do any disservices to making pregnancy a little or child birth 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 malades that are associated with poor birth outcomes or premature birth, preeacclampsia, 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. And and 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 Morasco. 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 OBGYn didn't want her in there after her water broke. Uh, 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 childirth because that's not a disease.
childirth because that's not a disease. That's not a sickness that requires intervention. Now, there are abnormalities if the 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. Yeah, I I agree. I I interviewed Marty Mackery about this a few months ago. I'll link to it in the show notes. is just a real eyeopener on how far we've strayed from elements of natural child birth that frankly could still be woven into a modern medical system where we can take advantage of the opportunity to prevent uh mother or child death in a pregnancy scenario. Uh 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, you know, give birth to twin boys that her pelvis was just not gonna let out. And so we we opted for C-section. But, you know, other things in the hospital like them being removed immediately, placed under lights, given the injections, taken away from mom, like like those are things that I think are are largely unnecessary. Don't wash that baby. you know, uh, put that baby right on mom's chest or in my case, it was dad's chest because, uh, my wife tore, uh, 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 um think about the um 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
baby doesn't know how to walk. It knows how to swim when it's born. I think that indicates that our ancient grandmothers g or mothers gave birth in the water. Yeah. Exactly. And maybe maybe we're just, you know, evolving on this water planet and eventually we'll be born with with webbed fingers and toes. Uh who knows? Um and I'm joking, by the way, for those of you who know. I'm I'm one of those six days creation guys. Uh but anyways, on to some other considerations. There is obvious resistance to some people to cold bath. Um I think honestly until you get used to it, even the friction of stopping on your way into the gym and jumping in cold water can sometimes be a stopper for some people. Like I'd rather people, you know, get in and do the workout and not have the cold bath actually stop them. Although, as Thomas noted, like 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 don't give it even more than 15 seconds before they're like, "Screw this, I'm out." But um the one thing that I'm often asked about is rain odds. 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 two weeks, the hands and the feet stop getting cold and I think is not based on research that it's a potential cure for reayods. Give me your thoughts on on reayods and cold plunging. Case studies agree with you. I have three case studies, one that I experienced directly and two that have been reported to me by others of women who have resolved the renose 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
that. You titrate exposure to the stress until the person becomes acclimated. Ren is not just a physiological phenomena. It's a feedback loop between the psychological and the physiological which is why some people will experience an extreme vasoc constriction response even if it's only like 60 ° 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 in living in uh Arizona for a while, probably had no brown fat. She experienced acute renods 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. You know, can I go in up to my armpits? Mom, this feels really good. How long have I been in four minutes? 5 minutes?" The little girl's 9 years old. She looks up to 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 °. We did the breathing. We talked her through it. Next thing you know, she's at 34 ° fully, you know, immersed up to her neck, hands in the water, wrote no rays 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 reos using exposure therapy. Most people get advice from their doctors that says, "Oh, you should stay warm. You should keep the thermostat higher." Yeah. Okay. Another topic. You say magnesium is critical.
topic. You say magnesium is critical. You mentioned magnesium earlier, but you actually say it's and 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 they 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 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 Morasco and then I don't shower afterwards. You don't have an issue with in the Morasco with the filtration or anything like that with putting the Epsom salts in? No. Put as sulfate salts. No chloride salt. Leave
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. 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. Um, okay. So, uh, 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, is going to cause you to go into adrenal fatigue because of the hypercortisol surge and the eventual adrenal exhaustion. Um, I doubt you deny that there's a cortisol release when you get into the cold plunge, Thomas, but what 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. You know, I see those accounts. I put up something on cortisol and, you know, 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 accurate that works out. There are three 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, you know, 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. Um, we brought in a bunch of research subjects. Uh, 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
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 raise 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, Reema Solanic. 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 two weeks. And in the clinical trials where they've taken people and acclimated to them to the cold over a period of two 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, you know, 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 overdo it. Like I do know some people or who watch, you know, and all they watch is, I don't know, the Tik Toks or whatever where people are going 10 minutes. I haven't said this in the video I did this morning. I'm 33 ° for me pre-workout, 60 to 90 seconds. And if I'm going there as part of like a sauna back and forth hot cold contrast, it's two to three minutes. I can't tell you the last time
minutes. I can't tell you the last time I was in a cold bath more than 5 minutes. Why would you be? Like two to four 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 gas 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. You know, if you have any, you know, you've started thermogenesis, you've got all the benefit, get out. Spot on. I have a client, uh, Brian. Hi, Brian. He listens to the show and he sent me a message the other day. He's like, "Dude, like I just, you know, 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 you have gone beyond the benefits. Like more is not better. Just cut it to I think he was going 5. I said, "Cut it down to to two, you know, or or three at the most. You don't have to be shivering uncontrollably for hours after you get out. You're not going to get 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 him good advice. When it comes to calories, it's counterintuitive. You've probably seen some of the videos where it's like, oh, you know, 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
those ketones spike when you get into the cold plunge and blood glucose goes out. 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 phenomena 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, you know, Morasco is going to help you lose weight, I'd probably sell five 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. Yeah. And maybe let's say the 180 extra calories you might burn by uncomfortably shivering your ass off for
uncomfortably shivering your ass off for two 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 not in my you know I'm I'm one of those embrace discomfort guys but uh that's not uh I think a great discomfort to embrace especially if you're fooling yourself and think is going to burn massive amounts of 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 hyperco compensatory 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 postmeal feeding occurs after cold plunging. Um, and and this is something I've seen in studies. So, you do need to be aware of that. Uh, 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 like heap a bunch of extra calories on your plate and expect to lose weight or get as many metabolic benefits from cold plunging. And 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. Uh you know, pumpkin pie is my downfall cuz 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 of Thanksgiving. 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
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 just like four minutes, you know, came out couple hours later, peed on a stick, ketones. And I was able to clear the glucose from my bloodstream. And by the way, pumpkin pie, it isn't the worst. You know, 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. Next Thanksgiving, It's kind of so good. You're right though. Any big feast today, uh, I cold plunge because of its effects on insulin sensitivity and even like 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 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 um also works is flip it around. If you find that you've overeaten and you enjoy it, you know, because it's great, you be like, you know what? Uh couple of things I can do, cold plunge, go for a walk, and I won't experience the same blood sugar spike, this postandial blood sugar spike as a result of overeating. Yep. It's It's uh a little bit more ballsy than a walk, but I think more effective. Um Thomas, this book is great. Uncommon testosterone: Cold Plunch 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 in the show notes at bengreenfieldlife. com. I'll also link to the Morazzco. think I have a special code that saves you like 350 bucks on a Rosco if you want like the Cadillac of cold tubs for yourself.
the Cadillac of cold tubs for yourself. Um Thomas, thank you, dude. This has been a pleasure. I'm so glad you like the book. I had you in mind, you know, and I'm in it. There's a page you are. I forget what I talked. What did I put in there? Cold plunge is Viagra for the whole body. I've listed that quote and it said Ben Greenfield is right. All right, you guys. Thanks for listening in again. in the show notes are at ben greenfieldlife. com / uncommon. I'm Ben Greenfield along with Dr. Thomas Seager of Morasco Forge signing out from bengreenfieldlife. com. Have an incredible week. Do you want free access to comprehensive show notes, my weekly roundup newsletter, cutting edge research and articles, top recommendations from me for everything that you need to hack your life, and a whole lot more. Check out bengreenfieldlife. com. It's all there. ben greenfieldlife. com. See you over there. Most of you who listen don't subscribe, like, or rate this show. If you're one of those people who do, then huge thank you. But here's why it's important to subscribe, like, and or rate this show. If you do that, that means we get more eyeballs, we get higher rankings, and the bigger the Ben Greenfield Life Show gets, the bigger and better the guests get, and the better the content I'm able to deliver to you. So, hit subscribe, leave a ranking, leave a review if you got a little extra time. It means way more than you might think. Thank you so much. [Applause]
Transcript auto-generated by YouTube. Verbatim — duplicates intentionally preserved.
This is a conversation that has implications for how millions of men and women structure their cold practice. The finding is counterintuitive, well-documented, and almost never discussed with appropriate precision.
200–300% Increase in norepinephrine from a single cold immersion session 34°F Dr. Seager's personal cold plunge temperature (1°C) 1,000+ Ice baths completed by Dr. Thomas Seager
Cold after exercise: testosterone suppressed. Cold before exercise: testosterone elevated. This is not a theoretical distinction — Seager has documented it across case studies, and the mechanism is coherent with what endocrinology has long established.
Post-exercise cold suppresses the inflammatory signal that triggers anabolic hormone release. The inflammation that cold is specifically used to reduce is part of the hormonal cascade that includes growth hormone and testosterone. Intercept the signal, and you intercept the hormone response.
Pre-exercise cold does the opposite. The hypothalamic-pituitary-gonadal axis responds to cold exposure by increasing luteinizing hormone. LH drives testosterone synthesis in the testes. Cold before training therefore arrives as a hormonal primer — elevating LH before the additional testosterone stimulus of the training session itself.
Women also produce testosterone — in amounts roughly ten times lower than men, but physiologically significant for energy, libido, mood, muscle function, and bone density. The assumption that testosterone optimization is a male-specific concern is both common and incorrect.
Seager's case studies included women, and the findings were parallel: pre-training cold plunge (discussed further here) produced meaningful testosterone elevations in female subjects as well. Most women are unaware of how beneficial testosterone is for them, and of how amenable their hormonal profile is to the same cold timing principles that apply to men.
This has implications for how women structure their training and cold practice — particularly during phases of the cycle when testosterone naturally drops.
Greenfield describes his experience with the Morozko Forge — Seager's ice bath, capable of maintaining temperatures below 34°F — with the enthusiasm of someone who genuinely relishes the extreme version of the practice. The ice that forms on the surface. The icicles that greet a morning plunge.
There is a psychological dimension to this framing worth acknowledging: some practitioners find that the ritual of extreme cold — the preparation, the entry, the exit — carries a quality of felt aliveness that more moderate protocols do not fully replicate. This is not science. It is phenomenology. And it is real.
The distinction matters because Seager is careful to note that the physiological benefits do not require the extreme temperatures that Greenfield describes. The hormonal effect plateaus. The psychological effect of the extreme experience is a separate variable — one that some individuals value and some do not.
For most people, the practical recommendation from this conversation is straightforward: if testosterone support is among your goals for cold practice, plunge in the morning, before training.
The full protocol Seager endorses for testosterone support: two to four minutes at 34–50°F, morning, before any strength or endurance training. Daily frequency produces the most consistent hormonal effect. The window of LH elevation lasts several hours, covering most morning training sessions.
If morning plunging is not feasible, the next best timing is at least four hours after training. This allows the post-exercise anabolic cascade to complete before cold attenuates it. The worst timing — cold within 30–60 minutes after a strength session — should be avoided if testosterone support is the goal.
Ice baths don't suppress testosterone — bad timing does. Cold before a workout boosts luteinizing hormone and raises testosterone. Cold after suppresses the very signal you trained to produce.
Women also get a big boost in testosterone from pre-training cold. Most women don't know how beneficial that is for them. — Dr. Thomas Seager
The physiological benefits plateau at a certain temperature. The primal experience of extreme cold is a different variable — valuable to some, irrelevant to others. — Dr. Thomas Seager
If testosterone support is a goal: cold plunge in the morning, before training. This is the timing that elevates luteinizing hormone and primes testosterone synthesis.
Avoid cold within 60 minutes of a strength session if building muscle is the priority. The post-exercise anabolic signal needs time to complete.
Women: the testosterone timing principle applies to you as well. Pre-training cold supports testosterone, which supports energy, mood, and muscle function regardless of biological sex.
