Science Friday - Are Cold Plunges Actually Good For You?

Episode Date: August 7, 2025

If social media and certain influential podcast hosts are to be believed, cold plunges can do everything from boosting your immune system to reducing inflammation to acting as an antidote for depression. But what does the science say? Joining Host Flora Lichtman to throw at least a few drops of cold water on this science of plunging is biologist François Haman, who studies human performance and cold exposure.And, with the help of the HBO show “Last Week Tonight,” a minor league baseball team in Pennsylvania rebranded themselves the Erie Moon Mammoths. That comes just a few months after the Utah NHL franchise renamed itself the Utah Mammoth as a nod to that state’s paleontological past. So, why are mammoths back? And do they really have what it takes to be a successful team mascot? Paleontologist Advait Jukar joins Host Flora Lichtman to weigh in.Guests: Dr. François Haman is a biologist at the University of Ottawa who studies how the human body responds to extreme environments.Dr. Advait Jukar is the assistant Curator of Vertebrate Paleontology at the Florida Museum of Natural History.Transcripts for each episode are available within 1-3 days at sciencefriday.com. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

I'm Flora Lickman, and you're listening to Science Friday. Today on the show, sorting fact from fiction on cold plunges, the hottest wellness trend. Morning, guys, it is day 87 of taking a nice bath every single day. Let's cold plunge together! I can't move. I don't know if that was smart, but I just did 20 minutes. If social media and certain influential podcast hosts are to be believed, cold plunges can do everything from boosting your immune system, to reducing inflammation, to acting as an antidote for depression.

But what does the science say about all this? Here to throw at least a few drops of cold water on the science of plunging is Dr. Francois Hamann, who studies human performance and cold exposure at the University of Ottawa. Francois, welcome to Science Friday. Thank you so much for having you. All right, let's dive in. Should I be plunging? That's my burning question.

So, and it is a burning question, which is interesting, because you'll be cold. you're not going to be burning. But when I started studying cold, probably 25 years ago, I was not expecting the trends that we're going to be happening now. So if you would have asked me back then, is it a good idea to jump in ice water? My answer would have been no. The dangers of it can be tremendous.

Really? Tell me about them. So the dangers are more related to the fact that ice water is a tremendously strong stress, which means that the body's going to be responding very strongly. And the first response you're going to get is cold shock. And even within cold shock, you could end up in cardiac arrest. You can have big changes in blood pressure. And this happens within the first 30 seconds. If you stay in there, you're stuck in there and you become hypothermic, then there's all the issues related to hypothermia.

And if you do it on a regular basis, you can actually develop what we call non-freezing cold injuries. And these non-freezing cold injuries have been amazingly well studied, especially in the military, context, I've done some work within NATO, and we've been looking at making sure soldiers know about these because it's going to create neuropathies and it will create permanent damage. So cold plunging is something you need to understand and you need to really see the science behind it and what you're actually trying to achieve. And so there are dangers, but there are also benefits. What do we know about the benefits? So the first benefit, which is kind of the obvious one is the fact that when I go into ice water, it's a stimulant. You know, it's going to wake you up.

It's going to give you energy. Dopamine will be released. That's clear. Endorphins will be released. Oxytocin, I'm not as sure, but oxytocin is potentially another hormone that would be released. So there is a feel-good sensation when you get into cold water. And most people, you ask, like, why do you do it? Doing some work in Switzerland, I was asking the soldiers, why do you do this? And they go, because it feels good. And that was their main answer, which is a answer because it actually feels good. So these are some of the benefits we definitely know. The ones we're not sure about that are all over social media is the whole idea of the

effects on inflammation. Very good paper written by Dr. Michael Tipton from Port Smith University showed that there might be a potential for a whole body exposure to ice water to actually reduce inflammation, but it's not clear at all. And it's not clear because the research is not well standardized. On the immune system side, there's no proof at all. that cold will improve the immune system. And again, this is something that is found all over social media.

The benefits that I see most of the time are more psychological. You know, people that might be, you know, suffering maybe from depression that are staying inside or making a decision maybe to go cold bathing and to be hanging out with people, doing it as a group. And that's definitely something that has tremendous benefits. So on the social side, achieving goals, pushing the limits are all. also some of the benefits that are very, very clear when it comes to ice water dipping. What about brown fat? What is it? Do I need to care about it? And how is it related to this

conversation? So the idea of brown fat is basically a furnace. So when you look at the mammalian world, it's a furnace that will be burning fats. And instead of going towards energy production, it goes into just producing heat. So the advantage, and that's what people are looking for, is that it can actually do it with you making no efforts. So the idea that's really attracting people is I could just be sitting there spending more calories without really doing anything. But the problem you have also is the brantad needs to be activated by cold. So you need to expose yourself to the cold. Even when you're exposed to the cold, the amount of calories being burnt are below five calories per hour and even less, which means that it doesn't, it doesn't

burn a lot of calories. And if you don't control your diet, you're never going to be able to modify your body weight. So the general idea is basically, can I lose weight using ground fat? It will not do that. So is it worth thinking about brown fat? Not really. Okay. You mentioned working with militaries in different countries. Tell me about this work and why they're interested in cold plunging. Well, there's a few reasons. I mean, the main reason is how do you operate in cold temperatures? Are you able to do your job and are you able to function to the maximum of your performance? So cold, if you look as a stressor, high altitude would probably be the top stressor, the lack of oxygen. Cold would be the second one.

Operating in the cold requires a lot of planning. You need to bring the right foods and you need the right behaviors to be able to survive. When most of the wars were happening more in warm areas, there was less focus on licking at cold per se. But now that the war in Ukraine has started, there's been more emphasis at how do we improve our capacity to operate in cold conditions? which is something that has been kind of left on the bag burner for the last few years, and now he's really coming back. And what's your work about? Is it training soldiers?

Is it studying them? So I did both. So again, as a researcher, studying is always something we're interested in doing. But I've kind of combined it also with workshops where I'm working with soldiers and working on, okay, how do we improve cold shock response? How do we improve the capacity through self-awareness to also? operate better in the cold. How do I make them understand? How can I sleep? How can I eat? And what are the behaviors that will optimize a chance of success? Well, can you give us some tips that we can

look forward to using in, you know, six months when it gets cold again? Yeah. So one of the most important things is to do an exposure that is gradual. One thing that's interesting is we tend to be too warm in the cold and we want to stay really, really warm. But the best way to survive, and do well and actually be able to even enjoy cold is to realize that in the cold, you might be cold a little bit. And just be able to tolerate that cold will allow your body to respond differently next time and actually improve your acclamation and actually be able to operate better. So I think one of the advices I would say is try to endure a bit of cold

because there will be benefits in your body's responses if you're able to do this. You know, some of the rhetoric around cold plunging online is that it's good because it stresses your body. And I confess that I don't totally understand the logic of that. But maybe you can help me understand. Like, is there something to that argument? Well, there is for sure. So one thing to keep in mind is that there are benefits of stressing your body. We leave in very thermal mutual conditions.

And that could actually promote some of the chronic diseases that we see because people are not really exposing themselves to various conditions. So if we think about the benefits of stressing ourselves, it's often what we do, we're looking for comfort. We're trying to feel good. We're trying to stay in a very controlled environment. And generally what we do is just kind of hilarious. I don't know the way it happens in the U.S., but in Canada,

we use a lot of AC to be super cold. And then in the winter, we're going to use a lot of heat to be super warm. But the reality of it is, stressing your body out actually allows your body to work to its maximum and be able to create plasticity in your responses. So if anything goes wrong, your body is going to be able to respond to whatever changing conditions you're going to be facing. And I think one of the issues is people are not looking for these changes in condition. And this is something that needs to be developed. And it's a bit developed through stressing your body out. And again, done in a controlled way,

in a safe way, but this will allow your physiology to improve when you're you're exposing yourself. Okay, I know we're just about out of time. Two quick questions. If I want to safely explore cold plunging, what are your top quick recommendations? So the first thing is to start gradually. One of the things is to really protect your hands and feet at all time.

You should not cool your hands and cool your feet. You will create damage. Anytime you cool your hands and feet, you increase the chance of developing non-freezing cold injury. So that's one very important. The other part is you don't need to start with ice water. You can actually start with water that is warmer and gradually come to colder temperatures.

So there's no real benefit to do ice water versus than just doing late water at 50 or 60 degrees. You're still going to get benefits. It's going to be more comfortable and you're still getting benefits of cold. And you're going to be able to stay in longer. So that's another thing. You should never do it alone.

You should always make sure that you have safety procedures in place, especially if you're doing it in lakes, especially if you're doing in the winter when there's ice, you've got to make sure you're able to come out of the ice just in case something happens. So you do have to follow some safety procedures. And I think what you have to be careful about is all these gurus on social media that are giving you advice on doing this with no real research understanding or research bragground and don't really understand the effects on the body. You do have to be tremendously careful about the advice. you get and make sure that you go to the right places to get your advice. I do fully encourage people

to get medical clearance before going into ice water. There is a risk of cardiac arrest. Do you partake in cold plunging? Yeah, I've been doing it regularly since 2017. I do it about three times a month. And generally, if I'm having very stressful weeks, I will tend to skip it and just go for cold showers. Why do you do it? What's in it for you? I love it. I just enjoy. it. I do it with friends. We go hang out. I love doing it in the winter. I love feeling the cold, which is kind of interesting. So I love feeling it on my body. I love coming out of the hole and feeling the sun, warming my body. So for me, it's really because I really enjoy it. And I really enjoyed the time in a group, but we never exceed two minutes. And we always supervise each other to

make sure that everything's good. It's like the soldier said. It feels good. It feels good. feels good. And, you know, we don't put enough emphasis on this component. And sometimes we should listen to the little voice inside and her intuition and what our bodies are telling us. If it doesn't feel good, don't do it. Simple as that. That is the perfect advice. Francois, thank you for taking the time and happy plunging. Thank you so much. Dr. Francois Hamann, professor at the University of Ottawa. Don't go away after the break. We're going to stay cool with a trip to the Ice Age to hang out with some especially charismatic megafauna. They have so much charisma.

They've got Riz, as the kids like to say these days. Stay with us. You might remember back in 1993 when the original Jurassic Park was released, it set off an explosion of dynomania in popular culture. Toys, theme park rides, even a basketball team, the expansion Toronto Raptors took their name and mascot from the film's Philoso Raptors. Now it seems another prehistoric animal might be having its mammoth moment. Ready or not, here come the moon mammoths.

The Erie Sewell's latest name change. With the help of the show last week tonight, a minor league baseball team in Pennsylvania rebranded themselves the Erie Moon mammoths. That comes just a few months after the Utah NHL franchise renamed itself The Mammoth as a nod to the state's paleontological past. So why are mammoths back? and do they really have what it takes to be a successful team mascot? We'll ask an expert on these woolly wonders.

Dr. Audvite Zucker is curator of vertebrate paleontology at the Florida Museum of Natural History, based in Gainesville, Florida. Welcome to Science Friday. Thank you. It's great to be here. Okay, so you study mammoths, let's get this out of the way. Yep. Are they or are they not mascot material? They are totally mascot material.

They're huge. The ones in North America were about 12 or 13 feet high at the shoulder. They weighed more than a big African elephant. They had these massive 12 to 14 foot long tusks. Big, massive, powerful creature. It's got everything that your team needs. Do they have charisma? They have so much charisma. They've got Riz, as the kids like to say these days. Were the mammoths here, woolly? You know, the mammoths down south in the U.S. were probably not quite a lot. as woolly as the ones up in Alaska and Siberia. The species that we have down here, the Colombian mammoth, was probably hairless. Hairless? Like an elephant? Just like a big elephant. Yeah, they ranged all the way from Central America, all the way up to the Great Lakes. And if you're down in Florida or Mexico or Central America, it gets pretty hot. I'm not sure if you want to have a big furry coat when you live down there.

That makes sense. Now that you say it, of course, it makes sense. Tell me a little bit about mammoth life. Reintroduce me to them. Mammots are very much like elephants. They probably lived in matriarchal herds just like modern-day African elephants and Asian elephants. They were large grazing animals, so they had these specialized teeth that were quite well adapted for feeding on grass. But that also meant that they could eat pretty much anything that they wanted to on the landscape. Mammots show up in North America about one and a half million years ago, and they're here on the continent up until about 12 or 13,000 years ago when they finally go extinct. Thanks to humans, or do we know?

Probably because of humans. This is a huge debate in paleontology and archaeology. And what we can say for sure based on the evidence is that you can't explain all of these extinctions without humans. Is there anything big happening in the mammoth field right now? There absolutely is. So you mentioned Jurassic Park. And one of the hallmarks of that movie is that they managed to extract DNA. Now, that's not really possible for extinct dinosaurs. But we do have ancient DNA from mammoths.

The oldest ancient DNA that we have from a mammoth comes from Siberia, and it's about 1.2 million years old. I think it is the oldest ancient DNA that we've ever extracted directly from a species. And we have ancient DNA from the Huntington mammoth, which was the basis for the Utah mammoth mascot. What we've found out kind of blew all of our minds. The Colombian mammoth, which is the species found in the lower 48 in Central America, is a hybrid species. About half of its DNA comes from woolly mammoths and half of its DNA comes from a lineage of step mammots that came down into North America about one and a half million years ago. That paper came out in 2021. So this kind of

blew up are conventional paleontological definitions for what this species is. What do you hope this extra attention brings to mammoths? I hope that it just rekindles people's appreciation for our deep past. I think there's a lot to learn about our past from these fossils, and a lot we can learn about the future from the extinction of these animals as well. So I think if we pay attention to what went on in the past, we can do a much better job of conserving our future. Okay, I'm sold. Major League Baseball, we're coming for you with the mammoths.

I mean, what's a met anyway? Yeah. Do you have a team you would pick to sub in the mammoth for? Maybe not the mammoth, but I live in Gainesville, and Gainesville High School, I think, should change its mascot to the Gompathare. And the gonfut there is a cousin of a mammoth. I mean, doesn't the Gainesville gonfethear sound awesome? That's a whole other segment. Absolutely.

And a gonfeter is a four-tussed elephant, and that's pretty rad. Okay, that's awesome, too. Thanks for coming on. Thank you so much. Dr. Audvite, Zucker, curator of vertebrate paleontology at the Florida Museum of Natural History. Thanks for listening. Don't forget to rate and review us wherever you listen, but only if you like the show. It really does help us get the word out and get the show.

in front of new listeners. Today's episode was produced by D. Peter Schmidt. I'm Flora Lichten. Thanks for listening.