Cold exposure has gotten a lot of attention the past few years, with people dunking themselves in ice baths for the sake of their health and well-being. But, good news here, exposing yourself to heat by sitting in the sauna or even a hot tub, might actually be even better for you, not to mention more pleasant.
In his new book, Hotwired: How the Hidden Power of Heat Makes Us Stronger, Bill Gifford unpacks the dichotomy of heat: how it can be both a danger and a healer. In the first part of our conversation, we dive into that former side, discussing what happens when your core temperature gets too high, why some people handle the stress of hot temperatures better than others, and how heat tolerance can actually be trained. We then talk about the advantages of heat exposure over cold exposure, and the benefits of heat for both body and mind, including how it can boost athletic performance and heart health, and may even be an effective treatment for depression. We also talk about how to get the most out of your sauna sessions and how Bill and I like to sauna.
Resources Related to the Podcast
- AoM Article: How to Sauna — All the FAQs
- AoM Article: How Saunas Can Help Save Your Body, Mind, and Spirit
- AoM Podcast #585: Inflammation, Saunas, and the New Science of Depression
- AoM Podcast #724: The Strange Science of Sweat
- Study reviewing the health benefits of “sauna bathing”
- Hotter’n Hell Hundred bike race
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Transcript
Brett McKay:
Brett McKay here and welcome to another edition of the AoM podcast. Cold exposure has gotten a lot of attention in the past few years with people dunking themselves in ice baths for the sake of their health and wellbeing. But good news here, exposing yourself to heat by sitting in the sauna or even a hot tub might actually be even better for you, not to mention more pleasant. In his new book, Hotwired: How the Hidden Power of Heat Makes Us Stronger, Bill Gifford unpacks the dichotomy of heat. How can it both be a danger and a healer? In the first part of our conversation, we dive into that former side, discussing what happens when your core temperature gets too high, why some people handle the stress of hot temperatures better than others, and how heat tolerance can actually be trained. We then talk about the advantages of heat exposure over cold exposure and the benefits of heat for both body and mind, including how it can boost athletic performance and heart health. It may even be an effective treatment for depression. We also talk about how to get the most out of your sauna sessions and how Bill and I like to sauna. After the show is over, check out our show notes at aom.is/heat. All right, Bill Gifford, welcome to the show.
Bill Gifford:
Great to be here.
Brett McKay:
So you got a new book out called Hotwired: How the Hidden Power of Heat Makes Us Stronger, and you take a deep dive into the research about heat and what it does to our bodies, both the good things and the bad things. You start out the book talking about how a bike race in Wichita Falls, Texas in the middle of August, led you to take this deep dive. What was going on there?
Bill Gifford:
Well, it sounds like a terrible idea, right? Riding your bike a hundred miles at a hundred degrees. I like to have a goal or a challenge that sort of then guides me and motivates my training, keeps me accountable, keeps me in shape. And I picked this one for some reason, I think because I’d always thought that I wasn’t good in the heat and that I didn’t do well in the heat. Back when I was a mountain bike racer in my thirties, twenties, and thirties, I always felt like heat was my kryptonite. So I wanted to kind of test that.
Brett McKay:
And so yeah, for those who aren’t familiar, this race, it’s pretty famous. It’s been going on for a couple decades. It’s a hundred miles and it’s again, in Wichita Falls, Texas. If you haven’t been there, it is west Texas. It is really hot in August and I mean people do get heat sickness and some people have actually died during this race because of the heat,
Bill Gifford:
A handful, and the heat is kind of the point. And weirdly you’d think, well, okay, nobody would sign up for this thing, but 10,000 people come and do it some years. It’s wild. And the year I did it, 2023, this, they call it a heat dome. So it was a super hot summer, a hundred degrees or more, pretty much all summer long. And then the day we did the ride got up to about 107 Fahrenheit. It was brutal. Frankly, I was surprised that I made it. And we can talk more about why.
Brett McKay:
Yeah, I mean, one of the things you do in this book is you talk about the research you did to prep for this race to see, well, what can I do so I don’t get heat sickness so I don’t die? And you talk about in the book, the very first thing you note is that heat can either kill us or it can help us. And let’s talk about how heat can kill us first. How hot is too hot for humans? Do we know that?
Bill Gifford:
We don’t really know. And it kind of depends. About 15 years ago, some climate researchers theorized that there was a theoretical upper limit past which humans could no longer cool themselves down. And it turns out that people were actually already getting into trouble at much lower temperatures. So for example, when there are heat waves in Europe, it’ll be like 90 degrees and that to you, you live in Oklahoma or to me in Salt Lake City, that seems like a relatively nice day in the summer, not too hot. So heat tolerance is very variable depending on a lot of different factors. But the interesting thing that I learned is that it can be trained, it can be altered. So it’s not something that’s kind of set in stone.
Brett McKay:
And I mean, you talk about people in India, kind of a contrast. There’s people in England where it’s like 90 degrees and they’re like, oh my gosh, we’re dying. People in India, they’re living in this sweltering, it’s super hot, super humid, and a lot of people do fine.
Bill Gifford:
I’m not saying it’s fun, but I did all kinds of crazy research for this. But I found one big study where they compare temperature and mortality rates across 400 different cities around the world, and they found that each city has an ideal temperature at which mortality is the lowest excess mortality. So it’s not too hot, not too cold. And by the way, many more people die from cold than from heat, 10 times as many, that was a stunning thing to learn because that’s not how heat is framed. So a city like Toronto, the ideal temperature or the minimum mortality temperature is like 66 Fahrenheit, and then for Tucson it’s like 86. So there’s differences basically. There’s differences in air conditioning, all that kind of thing. But I think a lot of it comes down to heat tolerance of these different populations.
Brett McKay:
Being used to it. What happens in our body whenever it does get too hot. It sounds like from the research you highlighted, it’s not so much the temperature outside our body that’s the problem. It’s our internal temperature – that’s what causes problems. So what happens when our internal temperature gets too high?
Bill Gifford:
We generate a tremendous amount of heat, internal heat, metabolic heat, just by being alive. And then when we do anything, like any activity, it’s almost like a car engine. Your car moves forward a little bit, but your engine is producing four times that much energy. So 80% of it is heat, like a waste product of heat. When somebody gets too hot, it is kind of gruesome. If you get to a certain point, you get into heat exhaustion territory, which is you feel wiped out, you feel confused, you feel kind of lethargic, you might pass out. So that’s heat exhaustion, not usually fatal. But then the next step is heat stroke, and that is what it sounds like. It’s a neurological situation. You can get aggressive, you can get confused, you can pass out, you can have a seizure. And as you’re unable to cool yourself off, as your temperature rises past 105, 106, 107, you get into a situation where your cell membranes don’t function as well, your cells kind of explode. You get into organ failure, especially the liver, and ultimately you die a horrible death. I mean, it is terrible. I’ve spoken to people who have had heat strokes. I’ve seen people having exertional heat strokes and it’s not pretty.
Brett McKay:
It’s scary. But the thing is, you can treat it. We know a lot more about heat stroke, thanks to research in the military is a big place where a lot of this research is coming out of as well as in athletics. So when someone gets heat stroke, how do you treat it?
Bill Gifford:
This is really important. If somebody is in that zone of elevated body temperature, confusion, heat exhaustion, heat stroke, you dunk them in a tub of ice water if you can. I mean, that’s the easiest that stops it in its tracks really. I went to a road race in Massachusetts, the Falmouth Road race seven mile run in August. It wasn’t particularly hot, but I sat in the medical tent with people from the Korey Stringer Institute, which is kind of devoted to this awareness of heat stroke and prevention of heat stroke. And we had runners coming in various stages of heat illness and we just threw them in the ice tub and they would come around, their body temperature would drop and they’d be okay. They’d walk out. Nobody needs to die of heat stroke. I think that’s the takeaway.
Brett McKay:
And what’s interesting about heat stroke, it can come on, as you said, with this race that you went to when it doesn’t seem that hot outside. Yeah, suddenly, because the issue is, I mean, one of the reasons why we don’t keel over and die when it gets really hot is humans are a species that can cool ourselves really efficiently. We sweat a lot, but for sweat to work, it has to evaporate. That’s what cools you off. So you sweat and then as the water evaporates, it takes heat away from your body. But when you’re in humid conditions, you don’t get a lot of evaporation. So you can run a race when it’s like 80 degrees outside, but it’s really humid. You can get a heat stroke in that because your body can’t cool itself off.
Bill Gifford:
Right. Falmouth was 70 degrees, 70 degrees in like 90% humidity and that length, seven miles, six, seven miles. So it could be around an hour, 45 minutes or an hour intense effort, and your cooling system doesn’t have a chance to catch up. That’s why those events are actually more dangerous than a marathon. But our cooling system is incredible. It’s this incredible gift that I think is one of our fundamental human traits. I mean, it kind of fueled our rise to dominance really.
Brett McKay:
Yeah, because it’s allowed us to basically migrate across the entire planet and live in just disparate climates. And then, I mean, you talk about this too. We’ve had the Born to Run guy. We’ve had Alex Hutchison on the podcast talking about why humans are so good at running. And one of the theories out there is that, well, we’re really good at persistence running. And so the idea is our early hunter-gatherer ancestors, they would just chase gazelles down and we could do it for a long time because we could sweat and keep ourselves cool. The gazelle couldn’t do that, and so it just eventually had to stop and cool off, and then that’s when we’d go in for the kill.
Bill Gifford:
Right. So if you think about walking your dog on a hot day in the summer, I mean, you can easily outlast your dog, I’m sure, unless your dog is some kind of endurance monster, but your dog can only cool itself by panting and you’re sweating across your entire body, and it’s amazingly potent cooling. I mean, we have these sweat glands that basically just bring water to the surface of our skin and then it evaporates, and that takes off a tremendous amount of heat. Brilliant.
Brett McKay:
What’s interesting though is that, and you alluded to this earlier, is that you can take two people and put them in the same sweltering conditions and one person could be completely fine and another person could have a heat stroke. What’s going on there? Why the difference?
Bill Gifford:
Right, right. I mean, fundamentally it comes down to different levels of heat tolerance, and there could be other things going on, certain medications, antidepressants for example, it could be a stimulant anyway that plays into it. Somebody could be drunk or hungover, but basically people have different heat tolerance. And the interesting thing to me is that, like I said earlier, this heat tolerance can be trained, it can be modified. So I went to the Korey Stringer Institute at the University of Connecticut, and it’s named after a football player who had passed away due to a heat stroke, a Minnesota Vikings lineman and his family helped found this institute. It’s dedicated to basically studying heat in athletes and workers. And so I did a heat tolerance test. And so basically to do that, they put you in a heat chamber, basically a hot room or a large oven, which is what it felt like, heated it up to a hundred degrees, 40% humidity, put me on a bike and just had me pedal for an hour. And then they monitored my body temperature and watched that go up and up and up and somebody who’s heat tolerant, their body temperature will go up and then it will kind of plateau. If you’re not heat tolerant, it’ll just keep going up and then eventually you’ll get into trouble. So mine just kept going up. So they were like, okay, you flunked.
Brett McKay:
Okay. So it’s trainable. You can become heat acclimated, and I think anyone who lives in a hot location during the summer has experienced this. Here in Oklahoma in the spring, it’s in the seventies, sixties, it’s pleasant. And then you have that first day that’s above 80 degrees and you’re like, oh, Jesus, this is unbearable. This is hot. And it’s because you lost your heat acclimation during the winter and the spring, and then by the end of August it’s 95, but it feels more bearable. You’ve gotten used to it.
Bill Gifford:
Exactly, exactly.
Brett McKay:
So what insights did you get from this research lab about what you can do to become heat acclimated? Are there protocols? Do we know how long it takes to get acclimated to the heat?
Bill Gifford:
Yeah, so this sort of protocol actually dates back to the gold mines of South Africa a hundred years ago. The mine owners used to think that, okay, every black person is heat tolerant automatically. They live in Africa, turned out not to be the case and people died. So they came up with a heat testing protocol, and then people who were not heat tolerant, basically the cure or the protocol is deliberate heat exposure over time. And so they would have these miners go into a tent that’s like 95 degrees. They set up these tents in the hospital, heated them up, and these guys would just shovel rocks for an hour and they would do that four or five times, test them again. Then if they were okay, they could go work. So it takes four or five sessions of an hour of getting your body temperature up to a certain level.
For me, it was going out on my bike ride for a while, get my body temperature up to 101.5 and kind of stay there for an hour. So I did that. I did 10 times as I was training for the hotter and hell a hundred, and I went into the ride thinking, this is a bad idea. This is not going to go well. I was scared. And then I kind of got out there, it got hotter and hotter and hotter and I was fine. I felt great. I couldn’t believe it. Actually, I had built up this heat tolerance by deliberately working out in the heat.
Brett McKay:
So again, heat tolerance is trainable.
Bill Gifford:
Yeah, I think I should make the point. I made sure to be safe and monitor my core temperature as I did this. So I had a little device called a core and it straps to a heart rate strap and it senses and calculates your core body temperature. So I knew I was never getting into the danger zone. So it’s really important for people who try this to be safe and not overdo it. And I think this also goes for what we’re going to talk about, which is more the sort of heat exposure by choice heat therapy, things like sauna.
Brett McKay:
Yeah. Something else you talk about is that there are some athletes who are using heat acclimation or heat adaptation not only to prevent keeling over in a race or a game, but also just as a performance enhancer.
Bill Gifford:
So as events like the Tour de France or the Olympics get hotter and hotter, heat has started to become, and heat tolerance has started to become a huge factor. And so they’ve had sort of star athletes and race favorites coming into these events and just completely bonking. They were fit, but they weren’t heat tolerant and it’s two different things. And so athletes started training their heat tolerance and then they found out that heat training itself actually brings some performance benefits similar to altitude training. So your plasma volume increases, you have more hemoglobin, more red blood cells, more oxygen carrying capacity. After I did my heat adaptation after I did the hotter and hell, I went back to Korey Stringer and I did the heat test and it was like a piece of cake. I was high fiving the lab guys and smiling and it was dramatic and it was a dramatic performance enhancement.
Brett McKay:
So heat can be a performance enhancer and it can also have a lot of other benefits, and that’s what the thrust of this book is about. So heat, yes, it can be bad for you, it can kill you, but heat stroke is preventable. You can adapt to heat and heat can actually be a big positive for your body and brain. Today we don’t really experience a lot of temperature variations. We’ve got climate control. So you can go from your air conditioned house to your air conditioned car. So let’s talk about this. What are some of the benefits of being exposed to hot temperatures?
Bill Gifford:
Well, I think cardiovascular is one side. If you’re in hotter conditions, your cardiovascular system has to work harder to keep you cool. There are these things called heat shock proteins at the kind of cellular level, they’re like little maintenance proteins or one scientist I spoke to called the mommy proteins, they kind of take care of other parts of your cell, other machines in your cell, they take care of your DNA. They kind of clean up age-related damage. So those get activated as you spend time in hot conditions. And I think it’s interesting that people, even though we live in this kind of comfort and I love sleeping in air conditioning, I’m not going to lie, but people gravitate towards things like temperature extremes, things like cold plunging and things like saunas. And I think we kind of crave that variation.
Brett McKay:
I mean, humans have been doing that throughout cultures and throughout time. So the Nordics have their sauna culture, but then other cultures have similar heating therapies that they do where they voluntarily expose themselves to heat. Russia has theirs, Japan has theirs in North America or the desert Southwest native Americans had sweat lodges. So yeah, I think there is this human need to experience extremes and temperature. It does something for bodies. So yeah, let’s dig more into these. This stuff is really interesting. So let’s talk about some of the benefits of heat exposure, voluntary heat exposure, you mentioned a few. It helps our heart health, and we know this because of some studies done on Nordic people who do sauna regularly,
Bill Gifford:
The Finnish, and this was sort of my gateway to this entire topic. I’d been because I’d written two books on longevity, I was aware of these really interesting studies from Finland where they looked at, it was really a sort of a broad heart health study. They were trying to figure out why Finnish guys were dying of heart attacks. And so they looked at a whole bunch of different lifestyle factors over decades. And so in 2015, this cardiologist and some colleagues came along and looked at the data and decided to compare sauna use and outcomes. And they found that the most frequent sauna users in this group had about half the rate or 40% the rate of heart attacks and half the rate of strokes and half the rate of mortality as the guys who used it once a week. Weirdly, they couldn’t find anybody in Finland who any of these guys who didn’t use sauna. So the baseline was once a week, so four to seven times a week did much better than once a week. It’s a huge finding. There’s no drug that does that. It’s a massive effect.
Brett McKay:
So what does the heat do? Why do we get that benefit to our cardiac system from heat exposure?
Bill Gifford:
Yeah, it’s primarily, it’s like light exercise I think is the best way to describe it. Your heart rate goes up, your blood vessels expand, your blood pressure drops, so there’s sort of a mechanistic effect on your cardiovascular system. So that’s one, that’s the first level, but I think there’s more to it. I think it may have to do with the fact that you’re activating, and this is a guy who had worked in this lab in Finland. This is kind of what they were pursuing, sitting in the super hot sauna activates your sympathetic nervous system, stressful, it’s the fight or flight, and then when you get out that sympathetic nervous system withdraws. And so they suspect that some of the benefits may have to do with how it manipulates your autonomic nervous system, which I thought was pretty cool.
Brett McKay:
That is cool. You also highlight research how sauna use or any type of other voluntary heat exposure can improve liver and glucose health. What’s going on there?
Bill Gifford:
Yeah, that’s a tough one. They did find that it appeared to improve insulin sensitivity, and they don’t know if that’s because it kind of sped up your heart rate’s going, your metabolism is speeding up. Perhaps it’s not clear,
Brett McKay:
But there is some sort of benefit. We don’t know the mechanism.
Bill Gifford:
And some of these healthy behaviors like sauna are kind of tied together. So it’s possible that somebody who’s using sauna more and maybe is healthier to begin with. We can’t discount that possibility. It’s a little tough to sit through a sauna, but it’s also possible that they’re doing sauna and they’re doing a little bit of exercise, they’re eating better or whatever. It’s hard to disentangle. They did find these finished researchers, they did parse that a little bit and they did find that the guys, and this was all men in this study originally, the guys who exercised and used sauna frequently had the biggest benefit. So they’re the ones that had the 50% drop in mortality, but the guys who didn’t exercise and just did sauna, they had about a 30% drop, so 30% effect. So that’s still pretty good. And that tells you that the heat does do something.
Brett McKay:
And then you also highlight research that there might be a potential connection between sauna use or hot tub use with our immune system.
Bill Gifford:
And hot tub use is just as effective by the way people love sauna and hot tubs aren’t as trendy now, but any kind of heat exposure, heat therapy, also infrared has been found to be effective. I think with the immune thing, that’s been something that has been researched actually for decades. And back in the day in the sixties, these German and Scandinavian researchers referred to it as, I think they called it hardening. So by doing the sauna and also the cold, which was part of it, people sort of toughened themselves up and were more resistant to infection. They missed fewer days of work and it’s not clear why.
Brett McKay:
That’s interesting. What about, I think a lot of people use sauna particularly because they, well, I go to the sauna, I’m going to sweat a lot, so I’m going to detoxify. Is there anything to this idea that sweating a lot detoxifies us?
Bill Gifford:
Yeah, I’m going to say I’m going to make people upset and say probably not officially. Sort of mainstream medicine will tell you that the only way we detoxify through our kidneys, through our liver and not really through our skin. So if you’re sweating things out, you’re just kind of sweating out the liquid that’s in your cells, the liquid that’s in your blood plasma. So if there’s a little bit of alcohol from last night that’s going to come out, but it’s not like a primary method of detoxification. There have been some studies that suggest that maybe we do put out things like heavy metals, but those aren’t very good studies. I’ll put an asterisk by that and I’ll say the jury is still out. It hasn’t been well studied. It might be that heat exposure accelerates the detoxification that your kidneys and liver do. Perhaps that’s a possibility. Brian Johnson did sauna protocol for I think a couple months and then he tested levels of various toxins in his body and also microplastics and those dropped by a lot, but that’s an of one. And it’s not a placebo controlled study, randomized study, but he does have access to pretty good testing methods. So I’ll say the question’s still open.
Brett McKay:
Yeah, still open. So potentially we don’t know.
Bill Gifford:
Potentially it does make you feel clean and it is back to your immune point. It’s a pretty clean environment. Not a lot of germs can withstand 180 degree sauna. And in fact, old time Finnish people like I’ve met Finnish people who were born in a sauna, they would give birth there sterile. It was the most sterile room in the house.
Brett McKay:
That’s interesting. So you mentioned this idea of heat shock proteins. I’ve seen this research before. It’s like, oh, when you expose yourself to heat, you activate these heat shock proteins and that can be good for muscle recovery and strengthen muscle gains. Is there anything to that?
Bill Gifford:
Possibly, but I think it has more to do with cellular resilience and going back to our heat tolerance conversation, there is a military study where they exposed, I think mice to repeated intense heat stress, almost like putting the mice in a sauna again and again and again. They tested their heat shock protein levels and they were through the roof and they found that these mice were extremely resistant to heat stroke. So it’s a protective mechanism I think as far as muscle gains, I think the increased blood flow I think plays a bigger role and that’s why sauna I think is in my opinion, preferable as a recovery or as a post-workout tool to a cold plunge.
Brett McKay:
Let’s talk about cold plunges because those, that’s been the rage now, we’ll say the past five, 10 years, everyone’s cold plunging. You got the cold plunge bro, and talking about it, talking, how do you know someone guy cold plunges? Well, he’ll let you know that you cold plunges and there’s all these benefits that are touted, increases. Dopamine helps with muscle inflammation, reduces inflammation. But you talk about those benefits are probably overhyped and cold plunges actually might be hurting your gains.
Bill Gifford:
Yeah, certainly. In terms of muscle growth, this has been pretty well studied and they’ve found that intense cold exposure slows down muscle protein synthesis. So after a workout, they actually did one crazy study where they had guys do legwork or subjects do legwork, and then they would put one leg in a warm basically leg container and the other leg in a really cold thing, and then they had them drink a special drink, blah, blah, blah, or they could see what was happening in each leg and the warm leg muscle protein synthesis was happening, cold leg, it wasn’t happening. So it tells you that you’re not getting the muscle gains. However, it may help with inflammation. It may increase dopamine, norepinephrine, all those things. It does that in the blood we’re not sure about in the brain. You have to kill the person to test that, so we haven’t done that. Also, it can give you, if you’re talking about jumping into a cold body of water, you’re getting into a territory where drowning is not impossible. If you suck in a big breath of water because of the shock of jumping in the cold, I mean that could be dangerous.
Brett McKay:
The cold plunges for after a workout, they’re like, well, it reduces inflammation. It’s like, well, if you strength train, your body needs inflammation for, that’s what causes your muscles to grow.
Bill Gifford:
Excellent point.
Brett McKay:
If you eliminate that inflammation, you’re just going to kill your gains, but you do highlight it could be useful. A cold plunge could be useful if you’re an endurance athlete. It can help with recovery. And it also just feels good going from the sauna to the cold plunge and back again, that can feel great and it’s okay to just do it, do the cold plunge and hot sauna together just for that. It feels good. But yeah, if you’re focused on building strength and muscle mass, maybe just stick to the sauna
Bill Gifford:
And you want to go in the cold plunge because you’ve built up all this heat in your body and sitting in a sauna, you’re hot. The idea of jumping in a lake superior sounds like the best thing. 40 degrees sounds like the best idea anybody ever had, and I’ve done it too. It’s just I think the science of cold is way behind the science of heat. But you made a great point about inflammation. Inflammation is not always bad, especially in the exercise context. Inflammation is part of what drives those adaptations, and it’s also a healing mechanism.
Brett McKay:
The other thing you point out too is when people do cold exposure, they probably get too cold. They get in a cold plunge that’s like 35 degrees when it really needs to be just like 50. I mean, it doesn’t have to be as cold as you think to get the benefits.
Bill Gifford:
Yeah, yeah. This is competitive cold plunging who can do the coldest cold plunge for the longest, and obviously it’s more challenging. I think people like it because a mental challenge, but this is very satisfying to learn from some of the experts I talked to that actually the ideal temperature for the physiological benefits is really in the fifties.
Brett McKay:
I mean, after I read that research about how cold plunging blunts muscle protein synthesis, I stopped doing cold showers after workouts, but I still do cold showers. I don’t do it for any health benefits. I just do it sort of like an exercise in willpower. It’s like, all right, I know this is going to be hard. I don’t want to do this, but I’m going to do it anyways, so that’s why I do it.
Bill Gifford:
And it makes anything else, whatever else you have to do that day, seem easier. And so I’ll do a cold plunge. I’m kind of like, oh God, do I have to do this? I won’t do it alone. But if I’m at the sauna with my son, we like to have little cold plunge duels. It’s social.
Brett McKay:
Yeah, it’s a great father-son bonding activity. Instead of playing catch, do some cold exposure. So going back to the heat exposure, getting the benefits of it, what temperature do you need to get to in a sauna and for how long do you need to expose yourself to that temperature to get the benefits we’ve been talking about?
Bill Gifford:
So this is interesting, those finished studies, they asked the subjects about how hot was their sauna, how long did they stay in, but it was just a one-time questionnaire, so it’s not super reliable. It did seem that the people who stayed in 20 minutes at above a hundred, I think 176 Fahrenheit did the best. I mean, having been to Finland, there aren’t any saunas that are cooler than 176. That’s on the cold end. I’m not sure we can definitively say that there is one protocol and certainly not one protocol for everybody. However, it does appear that a lot of the benefits that I’ve talked about and also some of the mental health benefits, so the heat adaptation, the heat shock proteins, those things, those happen when your core temperature gets up to 101.5 Fahrenheit. So I think that’s like 38 Celsius, so you have to get up to a certain core temperature. That’s kind of what it’s all about.
Brett McKay:
Gotcha. And there are ways you had this device that measured your core temperature that doesn’t involve sticking up a probe up your butt.
Bill Gifford:
Yeah, no rectal probe, no rectal probe, no Vaseline required, and I did endure the rectal probe a few times. It’s just a thing that they do.
Brett McKay:
My sauna protocol, I have a sauna in my backyard and I like to do it. I get it up to 190 and I’m in there for 20 minutes.
Bill Gifford:
Yeah, solid.
Brett McKay:
That’s what it is. And then if I have friends over for a sauna session, we want to talk, I’ll put the temperature lower and turn it more into a sweat lodge. So it’s like 120 and it allows us to talk for a long time, and then we just sweat a lot and then at the end we’ll crank it up and get it really hot and then jump into the pool.
Bill Gifford:
I think going back to our heat tolerance conversation, nobody should jump into 190 degree sauna for 20 minutes out the gate. Just pay attention to your sensations and pay attention to your body. I kind of go in for, I do 10 minutes at first, and then I kind of check in and like, okay, am I bored? Am I too hot? Am I not feeling it? Then I’ll get out, if not stay a little bit longer. I kind of stand past the point when I think about leaving, so I push that a little bit farther, and you have to make sure to give yourself enough recovery. Don’t just go out for two minutes and hop back in. You got to let yourself cool off.
Brett McKay:
Yeah, I drink a lot of fluids after
Bill Gifford:
That’s key, and electrolytes, by the way. This is where most of us in our French fry filled American diets, we don’t really need a lot of extra electrolytes. We get plenty, but if you’re intensively sweating or if you’re doing hot yoga or the hotter and a hundred, yeah, you need some electrolytes too, as I found the hard way.
Brett McKay:
How’d you find out the hard way?
Bill Gifford:
Oh, I went to a sauna festival in Minnesota and I was doing saunas all day long and hanging out, and I had a couple beers and I wasn’t really paying attention to hydration or salt. And then the next day I woke up and I just kind of felt miserable and I felt achy. I’d run a marathon. I was just super beat up. And then I talked to somebody and they were like, oh yeah, did you have any electrolytes? Like, nope.
Brett McKay:
Got to get those electrolytes.
Bill Gifford:
I didn’t drink enough, didn’t have enough electrolytes.
Brett McKay:
And so you also mentioned earlier that you can get these benefits from heat using a traditional sauna, like a finished sauna that uses wood or an electric stove to heat things up, an infrared sauna, hot tub. You can get the benefits with any of these things. Yeah. So one of the interesting sections that you have in the book, you talk about the mental health benefits of heat exposure, and there’s some researchers who are using heat exposure as a potential treatment for depression. This is coming out of a lab run by a guy named Charles Raison. We’ve had him on the podcast before. Oh, have you? Okay. Yeah, that was episode number 585. This is a long time ago. So for those who haven’t heard that episode and don’t know about this research, what do we know about heat therapy as a treatment for depression?
Bill Gifford:
Well, Chuck is great. He’s a real sort of intellectual explorer and he looks at all kinds of things that might sound extreme or cookie. He’s done a lot with eastern traditions. So the heat piece of it is interesting. He was involved with a study, I think the first study was in Switzerland, and they put these severely depressed people into kind of a heating device. So basically like an infrared sauna that you lie down in. And they heated these people up to, again, 101.5 Fahrenheit, and they found that basically their depression symptoms were wiped out, cut in half or more in some cases, completely gone. So really potent effect against severe depression, which that really surprised me because you think of a heat wave and really hot weather and people can get kind of grumpy, but this appeared to have this powerful effect against depression.
Brett McKay:
Do they have any ideas of why that is?
Bill Gifford:
They have some theories. People who are depressed appear to have a difficult time regulating their body temperature. In general. They don’t sweat as much. Their body temperature is elevated. So there’s something going on with the whole thermal regulation system in these folks. But one theory that these folks are working with is that if you heat up your brain to a certain level that stimulates a brain region. I think it’s called the dorsal Rafe nucleus to start producing serotonin. So similar to what SSRI drug might do. So that’s one possible reason.
Brett McKay:
If I remember correctly, another theory that Charles put out there is that using the sauna, exposing yourself to heat, it is an acute stressor. It causes an acute amount of inflammation. It’s like exercise basically. And then it goes away, and then it goes away. It reduces inflammation. He says it’s sort of like hair of the dog. You give someone, I think depressed people, they have a lot of inflammation in their body and in their brain. So exposing yourself to an acute stressor, it helps dissipate inflammation in the long run.
Bill Gifford:
And exercise does the same thing. And exercise also has a potent antidepressant effect potentially for the same reason is … it spikes, and then afterwards it drops and it stays down.
Brett McKay:
Yeah, that’s really interesting.
Bill Gifford:
Super interesting.
Brett McKay:
And then you highlight this, and I think Charles talked about this in our interview. He says, this heat therapy for depression, it doesn’t work for everyone. And I think the reason is depression can be caused by all sorts of things. It’s not just because your body isn’t how to thermoregulate or you have inflammation. It could be other stuff. So if your depression is caused by something else, the heat exposure is not going to do anything for you.
Bill Gifford:
The way they discovered this is really interesting, or one way they discovered this, they found that they were experimenting with this microbe that they found in the soil in Uganda, and they were trying to use it to help build up people’s immunity to leprosy. And it gives you a slight fever, but a fever is kind of a healing mechanism. And they found that people who had been injected with this microbe were happier. They got happier really after having this slight fever. Kind of a crazy story.
Brett McKay:
And you talk about in the book, you’ve had dealt with a melancholic disposition throughout your life.
Bill Gifford:
Yeah that’s why I’m a writer.
Brett McKay:
Yeah, same.
Bill Gifford:
It’s required.
Brett McKay:
I’m an Eeyore too. Did heat therapy do anything for your melancholy?
Bill Gifford:
Oh, it was amazing. It’s actually why I started gravitating towards heat in the first place. I started going to the sauna in my gym, which was kind of dark. Not the best, but it was warm and comforting, and I felt good being in there and I, I was going through some difficult work stuff, and prior to that, sauna was not on my to-do list. And so I kind of took that. I was like, Hmm, I felt better. I wonder why. Then I came along and I met Chuck Raison and did a little bit of a dive into that research, and then I actually volunteered to be sort of a guinea pig in a study that he and his colleague Ashley Mason were doing in Colorado. And basically they stuck me in this infrared sauna lying in a hospital bed again with the rectal probe, but anything for science. So they heated me up for an hour and it was totally miserable, and I was like, why did I do this? But I was kind of bummed out. So we did this, and then I hopped in a cold plunge and I kind of went home to the hotel thinking, why the heck did I do that? But then the next day it was like the skies opened up and the angels were singing, and it was like, I hadn’t felt this good in months. I couldn’t believe it. It was euphoric. It was amazing.
Brett McKay:
That was the thing that drew me to sauna was the mental health benefits. I’d go there. I’d have this natural drive to go to the sauna whenever I was feeling really stressed out, and that’s why I started it. And if it helps my cardiac health, great. And if it helps heat shock proteins fantastic. But I do it primarily because it just makes me feel better mentally.
Bill Gifford:
Yeah. There’s something about it. And I do the same thing. I go to the sauna place kind of near my house and spend an hour going in and out, and then I’m just driving home and I don’t care. I like somebody cuts me off, don’t care. I can tackle the work things that I’ve been putting off. I’m just better to be around afterwards. It’s great.
Brett McKay:
So I think when a lot of Americans in particular talk about hitting the sauna or doing heat therapy, we typically talk about it as a biohacking tool. We’re like, I want to improve my heat shock proteins, and I want to improve my cardiac health, whatever. But you argue that taking this, it’s a really reductivist view of heat therapy can miss the bigger benefits of heat exposure. What can Americans learn from Nordic sonic culture and heat therapy about some of those intangible benefits of exposing yourself to the heat.
Bill Gifford:
And those mechanistic benefits are real. But I think it comes down to how do you approach, how do you think about time? And so here we’re like everything we do has to have a purpose and a payoff. It has to have a concrete, okay, I’m doing this and I’m checking this box, and I’m taking down my blood pressure and I’m activating my heat shock proteins. I think in more traditional sauna cultures and heat bathing cultures, it’s really about taking time to, as one person told me to slow down. So you’re going to a third space, you’re not thinking about work, you’re not thinking about status. You’re not necessarily there for a concrete health benefit, but it’s just taking time for yourself or to be with your family or your friends and to do something that doesn’t necessarily need to be quantifiable or productive.
Brett McKay:
And those Nordic cultures like, it’s a social activity.
Bill Gifford:
It’s social. Yeah. I mean, the benefits, I think the social benefits are tremendous, but I think if you’re doing it by yourself, it’s almost like a meditation. You’re just slowing down. You’re away from your phone, you’re away from work.
Brett McKay:
For me, I mostly sauna by myself, but when I’m in there, it’s like, no phones are allowed. … I’ve taken my phone into a sauna before and you’ll eventually get this warning saying, your phone’s too hot, take it out. But I just go in there and just close my eyes and just really relax and just don’t think about things. But I do think it’s an even more enjoyable experience when you can do it with friends.
Bill Gifford:
Yeah, it’s nice. It’s a good little bonding thing. There’s something about it. We’re in this space that is kind of too hot and kind of slightly panicking, a little bit where it’s stressful, but you’re together. So it breaks down inhibitions, I find also. So in New York where people walk around with their guard up, these social saunas are hugely popular, and you go in and you talk to people. It’s crazy.
Brett McKay:
Well, yeah. You mentioned that in that study with the people about depression and sauna treatment, one of the things they noticed, they started talking. People just start talking and they’re just yapping. And you did the same thing. You just started yapping to this guy.
Bill Gifford:
Yeah, I was just babbling like a madman.
Brett McKay:
Yeah. That’s really funny.
Bill Gifford:
And I’m not the chattiest person typically, but it somehow broke down those inhibitions.
Brett McKay:
What do your sauna sessions look like these days?
Bill Gifford:
So there’s a couple places in town that I go to. One place is super, super hot, and so I debate with the guy, I think your song is too hot. But anyway, the cold plunge is awesome. It’s clean, which is I think an important quality in a cold plunge, especially a public cold plunge. So yeah, it’s real basic, right?
Brett McKay:
One thing I noticed cold plunges, and I’ve been wary about doing public cold plunges, whenever I’ve done cold plunges, I have to pee you immediately. There’s some response. I think there’s some response in your body once you hit cold, you’re just like, I need to pee. So I couldn’t imagine doing a public cold plunge because the only thing I’m thinking is people probably just pee in the thing.
Bill Gifford:
You just ruined it for me, I think. Yeah,
Brett McKay:
I’m sorry. Okay. So you do the sauna, you do the cold plunge, and how often are you doing, doing this?
Bill Gifford:
Oh, I do once or twice a week at this point. So I’m like the control group in those finished studies, but it’s enough, and I go when I can take the time it takes. It’s like an hour. And so in fact, I’m going to try to go today and get my kid to go. He’s home from school. So that’s going to be the afternoon, and I go in the afternoon, I go at four. So I’m kind of done with any kind of productive writing I’ve had to do. So relaxing that I want to go to sleep afterwards.
Brett McKay:
For me, I have a sauna in my backyard. It’s one of the best purchases I’ve ever made.
Bill Gifford:
That’s so great.
Brett McKay:
It’s fantastic. You just go in. I go in after a workout for 20 minutes, but it’s awesome. I love it.
Bill Gifford:
Yeah. I feel like I should get one now, but I haven’t pulled the trigger, but I don’t necessarily want to always sit in there by myself.
Brett McKay:
You like the social aspect of it.
Bill Gifford:
So maybe that’s a trigger for inviting people over and having sauna days.
Brett McKay:
Yeah, inviting your friends. Well, if I’m ever in Salt Lake, I’ll hit you up. Well, we can do a sauna session.
Bill Gifford:
Yeah, yeah, for sure.
Brett McKay:
Bill, this has been a great conversation. Where can people go to learn more about the book and your work?
Bill Gifford:
Yeah, the book is called Hotwired, and I’m on Instagram and the site formerly known as Twitter at Bill Gifford. I’m also on things like Threads, so you can go there.
Brett McKay:
Well, Bill, thanks for your time. It’s been a pleasure.
Bill Gifford:
Yeah, Brett, thank you. Great questions.
Brett McKay:
My guest today was Bill Gifford. He’s the author of the book, Hotwired. It’s available on amazon.com and bookstores everywhere. Please consider sharing the show with a friend or family member you think would get something out of it. As always, thank you for the continued support and until next time, this is Brett McKay reminding you to not only listen to the podcast, but to put what you’ve heard into action.
