How Sauna Supports Cardiovascular Health and Mood

Dr. Rhonda Patrick: Deliberate heat exposure, and when we say deliberate heat, it's it's really you know you're you're going into a hot environment, right? So you're you're going to do something like a hot sauna, steam room, a hot bath, something that is you know either either the ambient temperature of the room is elevated or the the water and your body is like you know submerged in the water, right? And what is that doing? Well, that is actually. Kicking on a physiological response that is, in many ways, very similar to moderate-intensity aerobic exercise. Because when you are exposed to this deliberate heat exposure, when you're exposed to the ambient, you know, increases in temperature, you're elevating your core body temperature, which is what's happening with physical activity.

Your heart rate increases. Your plasma flow increases, your stroke volume increases. All these things that are happening during physical exercise are happening during this deliberate heat exposure. And so there's, like, there's, like, somewhat of a, I would say, mimicking effect of moderate-intensity aerobic exercise. And there's actually been studies that have compared that head-to-head. So they've looked at being on a stationary cycle doing, you know, not anything crazy, but, like, 120 watts. And then comparing that to sitting in a sauna for 20 minutes, doing each of those for 20 minutes. And they were comparable in terms of heart rate elevation during the physical activity or during the heat exposure, the changes in blood pressure during the activity, and then the improvements after.

So blood pressure improved after the stationary cycling, blood pressure improved after the deliberate heat exposure. Heart rate, resting heart rate improved after the stationary cycling, and resting heart rate improved after the deliberate heat exposure. So in other words, there's comparable effects with respect to, you know, cardiovascular adaptations that are occurring during deliberate heat exposure. And so that's one sort of, I think, important framework to think about is There is a mimicking effect. And why is that important? Well, certainly, it's important for people that are disabled, people that can't go for a run or a jog or even get on a bike, right?

And so, it's really important for that population of people, but it's also important for the population, I think, of people that won't get on a bike or go for a run, or they would rather just feel like they're sitting in a spa. And at the very least, or maybe people that are just so adverse, there are people that are so adverse to cardiovascular exercise that if you can just get them into a sauna, and we can talk about parameters in a minute, but, like, if you can get them into something that's sort of at least mimicking the moderate-intensity cardiovascular exercise, and they're getting those adaptations, those cardiovascular adaptations that they would get with at least a little mild to moderate-intensity exercise, That's going to be beneficial in the long run as well.

And then it's also beneficial for people that are physically active. You might go, well, why is that? And so being physically active, like being aerobically active, doing aerobic exercise, one of the best benefits is it improves what's called cardiorespiratory fitness. And that's probably one of the, I would say, one of the best biomarkers of longevity, like concrete things that you can measure. It's measured by by measuring something called VO2 max. It's the maximum amount of oxygen you can take in during maximal exercise.

And cardiovascular exercise improves that, particularly if you're doing a high-intensity exercise training, things that are like high-intensity interval training, for example, is one of the best ways to improve it, especially if you're doing longer intervals of, like, at least a minute. But what's interesting is that there's been data showing that people— so there's been 2 types of studies, observational data looking at people that just routinely exercise, or people that routinely exercise and do the sauna. And then they measured these, you know, there was measurements of cardiorespiratory fitness. And it was pretty clear that people that routinely exercised and routinely did the sauna had a better cardiorespiratory fitness than people that only routinely exercise.

In other words, there was a benefit to do sauna on top of the exercise, right? And then there's been intervention studies where it's like, okay, we're going to take people give them an exercise workout, I think it was a stationary bike, and then right after that exercise workout, they're either going to just do passive recovery or they're going to go into a sauna and recover for 15 minutes. And there was, I forgot how many weeks it was, something like on the order of 4 weeks or something like that. They measured cardiorespiratory fitness and a variety of other biomarkers like lipids, like LDL, total cholesterol, blood pressure, things like that.

And while there was improvements, obviously, with exercise, the ones that did exercise plus the sauna had an even greater improvement in their cardiorespiratory fitness. So their VO2 max was improved even more than exercise alone. They also had greater improvements in blood pressure and greater improvements in their lipid numbers and things like that. So there was every reason to add deliberate heat exposure on top of exercise as well. I want to pause here for a second for 2 reasons. One, you're the reason I have a sauna. I think I first came across your work and you had this 70-page website on the benefits of a sauna. And I remember skimming the first 3 pages of it going, I really need a sauna. And so you're the reason I have a sauna.

Shane Parrish: But when we say doing the sauna, what does that mean in terms of In terms of temperature, in terms of duration? Is a hot tub the same as the sauna? Talk to me about that.

Dr. Rhonda Patrick: A lot of the studies that have been done on sauna have come out of Finland, where they're using Finnish saunas, which are, generally speaking, it would be what I would call like, it's a regular sauna where you have like an electric heater with some rocks that are hot. In Finland, they often use water and they pour it on the hot rocks. And so there's a humidity aspect there, anywhere between 10% to 20% humidity. So a lot of the observational studies and intervention studies showing, like I just mentioned one about VO2 max improvements, blood pressure improvements, they're done in Finland.

And a lot of those parameters used, generally speaking, are, you know, regular saunas of about 175°F and 10% to 20% humidity. The average time spent in the sauna is about 20 minutes for the benefits to really be, I would say, robust. And then there's frequency, right? So, like, how often do you do it? And so there've been a variety of studies that have looked at all-cause mortality, so, you know, dying early from all causes that are non-accidental, and then looking at cardiovascular-related mortality, like dying from a heart attack, for example. And people that are more frequently using the sauna, it's a dose-dependent effect. So people that use the sauna, for example, 2 to 4— sorry, 2 to 3 times a week have a 24% lower all-cause mortality compared to people that only use it 1 time a week.

But people that use it 4 to 7 times a week have a 40% lower all-cause mortality compared to people that only use it 1 time a week. So in other words, it seems like the minimal effective dose to get the most robust effect would be 4 times a week. And the same goes for other parameters. So cardiovascular— dying from, you know, cardiovascular-related mortality, it's 50% lower in people that use the sauna 4 to 7 times a week compared to 1 time a week. Whereas if you're only doing it 2 to 3 times a week, it's something like 27% lower. So frequency matters as well. And when I said duration in the sauna, it's really important.

So those studies were also done looking at, okay, let's say people are only staying in the sauna for 11 minutes versus, like, greater than 19 minutes, so, like, 20 minutes, right? They didn't have that robust 50% reduction in all— sorry, in cardiovascular-related mortality if they only stayed in for 11 minutes. It was much less. It was a little bit, like, it was improved, but it was not 50%. So the temperature, and the duration, and the frequency, those are 3 parameters that are important with respect to using, you know, a regular hot sauna. And when I say— the reason I say regular hot sauna is because another type of sauna that's very popular are infrared saunas. And infrared saunas do not get as hot, so they're not warming the ambient air around you.

They're working through another mechanism, and they're sort of like moving molecules inside your body around and sort of heating you up in a different way. And you do sweat a lot, and you do get your— You can get your core body temperature elevated, particularly if you stay in quite a long time. But you do have to keep in mind that you can't take those parameters and go, I'm going to stay in a 145-degree infrared sauna for only 20 minutes, because that's what those Finnish studies have shown, because they're completely different in respect to, you know, the ways that they're working. And so there have been studies that have compared, for example, like a head-to-head comparison of like a regular hot sauna versus an infrared sauna, and looking at things like blood pressure improvements.

And if you're just staying in for 20 minutes, like the same amount of time in each, you're not going to get those blood pressure improvements from an infrared sauna, which makes sense. It's not as hot, right? You're not— it takes longer to elevate that core body, to get your heart rate elevated. And anyone that's done, like I've done a lot of infrared sauna, and I've done a lot of regular hot sauna. You know, I know, and also wearing a heart rate monitor, right? You can wear like your Fitbit or your Whoop or whatever into the sauna, and you'll know when your heart rate starts to get elevated. And it's not going to be after 20 minutes in an infrared sauna. Now, so that's important to keep in mind that, you know, you just have to kind of increase the duration in there.

For me, I have to stay in like 45, like I'd say 60 minutes is more like the duration that I would have to stay in to start to get more of elevations in my heart rate. Again, that's that mimicking of the moderate-intensity exercise. But there's also biomarkers that have been measured. So, for example, we haven't gone into this yet, but heat shock proteins, these are one of the adaptations that happen when your body is forced to increase its core body temperature, whether that's through physical activity, which is making you hot and making you sweat, or if deliberate heat exposure. And studies have been done looking at people that go into a relatively hot sauna, so this would be a 163-degree Fahrenheit sauna.

If they stay in for 30 minutes, they can raise their heat shock proteins about 50% over their baseline levels. And heat shock proteins have a lot of beneficial effects. So they're involved with preventing proteins from aggregating and forming plaques in the brain, in the vascular system. They also are very important for preventing muscle atrophy. And there have now been studies that have been done showing that just even locally heating a person's, like, leg, let's say they're, you know, so the studies that have been done have been, like, they're called immobilization studies where they're sort of mimicking an injury or an event. Like, let's say you go and, like, an older person goes into the hospital, they have the flu, whatever. They're basically immobilized for a period of weeks.

And so they're not using their muscles and their muscles were atrophying at a rapid rate, right? Well, studies have been done where if you apply even just local heat, that you can cut that disuse atrophy by as much as 40%. And animal studies have looked at mechanistically, they've repeated this, and they've shown that it has largely— it's due to the increase in heat shock proteins. So heat shock proteins are a good biomarker for heat stress. So is increased heart rate. We talked about, like, you're getting up to 110, 120, you can get up to 120 beats per minute sitting in the hot sauna, and that's really an indication that you're core body temperature is being elevated, your body's doing that work.

So you asked about hot baths, and there have been studies looking at hot baths and heat shock proteins. And you can elevate your heat shock proteins by being submerged from the shoulders down for about 20 minutes in about 104°F water, which is the standard hot tub level. So hot tub heat level is what I should say. So I do think there are comparable effects with respect to the modality of heat exposure, whether we're talking about a hot sauna or a hot bath, perhaps an infrared sauna. Again, the duration, the parameters will change. The parameters will change. But I do think that you can find comparable effects. There are personal preferences at play. Like, I like both hot tub and hot sauna. I find that I cheat more with a hot tub.

Like, I'm like more prone to put my arms out when I get really hot. I'm in the sauna, there's nowhere to go, right?

Shane Parrish: Right. If I'm getting hot, then I have to get out and then I'm like, oh, I'm giving up. Mentally, I'm like, no, I'm not going to give up. But if I'm in the hot tub, I don't feel like I'm giving up when I'm just getting my arms out. So there's reasons, this is my personal anecdote, but there's reasons why I like to do both, but I really like to do the sauna because I feel like I'm so much less likely to cheat with respect to making sure I don't So, yeah, I mean, and then, of course, there's many benefits to using the heat exposure. We talked about the cardiovascular benefits.

Shane Parrish: There is an immune benefit too, like your immune system is— There is, yeah.

So there was— there have been some observational data studies as well looking at, like, pneumonia risk. I think it was something like 40% lower in people that use the sauna 4 to 7 times a week. There have been a lot of really early studies on— again, these are coming out of Finland where there's humidity. So, you know, there's steam involved as well. And, you know, you're working your cardiovascular system. I mean, the lungs are affected. And I don't know all the mechanisms, and I don't know that they've all been worked out, but there is some sort of benefit on the lungs and also just the immune system as well. It seems like immune changes happen as well.

Shane Parrish: It is funny. I do get into the sauna when I'm feeling a little under the weather, or even if I am sick, because I find it's easier than getting on my Peloton. I get in there and I'll do the steam, and I feel so much better. It's like, there's my grandmother or grandfather used to tell me, like, sweat it out. And there's almost like something true to that when you are feeling sick. Well, absolutely. So when you're sick, you get a fever. And the fever response, your core body temperature is elevated, and heat shock proteins are activated. And heat shock proteins do play a role in what is called the innate immune response. So that's the immune response that you have when you've never seen a virus or a bacterial pathogen before.

It's that, like, it's not the antibody response, it's that, like, okay, let's fire away and get— so heat shock proteins do play a role in that. And when you are getting in the sauna, when you're doing some form of deliberate heat exposure, you are elevating your core body temperature. And so the fever response is a very important part of our immune system's way of dealing with the pathogen, right? It's important. Like, we get a fever for a reason. And so there's a lot of similarity there, right, between the deliberate heat exposure and the fever response. And it's interesting because the reason I actually got into the sauna way back in, like, 2009 had nothing to do with cardiovascular effects or, you know, even the effects on muscle mass, But it was the effects on my mood.

And that was, you know, I was very stressed out in graduate school, and this was like 2009. And I was using the sauna every morning before I would go into the lab and do my experiments that would often fail. It was very stressful. And I started to notice quite quickly that I was able to handle that stress a lot better. I was just, I was like, I wasn't getting so depressed after and so like down and anxious. And that's when I was like, something is going on here. Like, it was very noticeable for me. And so then I started to look into the literature and come up with my own sort of theories, which I— connecting the dots where I actually did publish on this back in 2022. It's in my huge review article on the sauna. It's called How Sauna Use Can Increase Healthspan.

And I think it has to do with when you get into the sauna, again, you're mimicking a lot of the same effects that cardiovascular exercise And so, you're releasing a lot of endorphins as well. Those are the feel-good opioids that we release in our brain. But what's really interesting is that also the opposite of endorphin is called dynorphin. So, it's also an opioid that we release in our body. And it's that opioid that's involved in the discomfort feeling. So, when you're working out, when you're getting hot, you're feeling uncomfortable. Your body's making dynorphin. And dynorphin is— part of what it does is it cools down your body. So it's playing a role in— it's like, okay, you're getting— you're elevating your core body temperature.

And so the adaptive response is, okay, we need to cool down somewhat. Dynorphin plays a role in that. But it also is what's responsible for that uncomfortable feeling when you're like, oh, I'm so hot, I want to get out. And what was super interesting that I sort of dove into at the time was that when you release dynorphin, you have a response, a feedback loop in your brain where dynorphin causes your body to make more receptors to the feel-good endorphin, and it sensitizes those receptors. And it makes sense if you think about it, right? When your body's not feeling good, and you're getting that uncomfortable feeling, it wants to make sure that it's going to counter that with feeling good. And so you start to like—

Shane Parrish: Yeah.

And the next time you make endorphins, from a hug from your child or a joke you laugh at, whatever, you're gonna feel even better because you're gonna be more sensitive to those endorphins from those— it's called mu opioid receptors and that's what you make when you increase endorphin. Anyways, that was a sort of, you know, I would say rabbit hole I went down many, many years ago. But now there's lots more research coming out. So work from Dr. Charles Raison and now his protégé, Dr. Ashley Mason, who I've been a collaborator with, and Tiny Foundation has funded a lot of her research that's being done. And she is using infrared saunas. It's a type of sauna that's like a— it's like a bed, and it's a chamber with the head out. And so your whole body is in it.

And the research that's done in her lab, and that was previously done in her mentor, Dr. Charles Raison's lab, is they are elevating your core body temperature to about 101.3 degrees Fahrenheit. So you're getting a fever. Yeah. They're inducing a feverish response. Many people have to be into in this sauna, and it's an infrared. It gets up to about 145-ish or something like that, and they're in there for like 60 minutes, any 50 minutes to 60 minutes, and they are getting they're getting a feverish response. So it's not it's a it's a very intense procedure. And what the first what Chuck Raison showed in the first study was that they could just do this one treatment, and it was actually a different type of infrared sauna, but I won't get into that.

And but they induced this feverish response, 101.3 Fahrenheit, just one time in people with like major depressive disorder. And they or they did a sham control where they made them feel like they were getting hot, but it like wasn't hot enough. It wasn't inducing that fever response. So they were it's called like a sham control, or it's like they're getting the placebo effect because they think they're getting the treatment. And the people that got the active treatment had an antidepressant effect that lasted like six weeks after, and it was like enormous and crazy. Placebo group didn't get it at all. And so now Ashley Mason has kind of carried the torch on, and she's doing these studies. And she's very, very promising data, fingers crossed.

I know it's like in, I think it's in submission right now for peer review. But she's done like 4 sessions, in some cases, some people did 8 sessions of it. And it's just amazing the effects that it's having on people with respect to the antidepressant effect. It's amazing what our body can do to heal itself when, you know, we're not sort of always injecting it with stuff too. There's all these other ways to go about healing it. It's almost like it knows what it's doing sometimes.

Shane Parrish: It does. I agree with you.

Dr. Rhonda Patrick: It is so exciting to potentially have a non-pharmacological treatment for depression because, you know, and I've shared a lot of studies on, like, Twitter and talked about, like, there's now— it's undeniable that doing aerobic exercise, like, they've compared running to classical antidepressants like SSRIs, so serotonin reuptake inhibitors, right? And it's the— in terms of the antidepressant effects, it's like the same, only the running has all the other benefits, right? But like, some people point out that like, there's people that are really severely depressed that like just can't even get out of bed. Like they're not going to go for a run. And it's true, there are people that will not get out of bed. But will they get into a sauna? I mean, it's a lot easier.

And so it really opens up doors that are just It's just so exciting.

Shane Parrish: It is also promising as we age, for the aging population. A lot of people who don't want to exercise when they get a lot older or the, you know, the aches and pains, and maybe it's a low-intensity way to do that. I can say for myself during COVID was probably the, you know, one of the most stressful periods of my life. And the sauna, like, you know, I think it saved my life a lot. You know what I mean? Like it, I was using the sauna 5, 6 times a week. And it was just sort of like, A, it was mentally grounding. It was something I looked forward to. It was a great ritual, but it sort of kept me out of trouble for some reason. And I could never explain it.

And I'm an N of 1 and, you know, I'm not super scientific and all that, but I was like, this is working. This is keeping me like happy and going and motivated. And I gotta keep doing more of this because, uh, yeah, it was really crazy.

Dr. Rhonda Patrick: Totally. I was the same. I mean, the same way for me during, during that period I was doing the sauna, like I was doing it like every day. I mean, it was like, you know, and again, but I had known, I was like, this does affect my mood. And again, it comes down to like probably a lot of things we don't really know. Is it immune related, the opioid system, everything, like all combined? Like there's a lot to unpack. I didn't care why it worked. Yeah, it just worked, right? I knew it was working. I'm like, I don't care if this is a placebo. Like, this is great.

Dr. Rhonda Patrick: I am glad it is not. And, you know, I still religiously use the sauna. But people that don't— can't afford a sauna, you know, it's not like— so like in Finland, it's ubiquitous. Everyone, I mean, it's like everyone has it and there's public saunas that are free. And, you know, we do have saunas in gyms here, but like it is nice to know. And I do think that if you can— most people do at least have a bathtub. And I think if you get one of those like little pool, like temperature gauges, like where you can measure the temperature and you get your bath up to 104 and make sure you maintain it at that temperature, you might have to keep turning on the faucet for 20 minutes and stay, stay in the water, like that is something that can also be done. And it is a powerful form of deliberate heat exposure as well. And it's nice to keep that in mind.