- Welcome to the Huberman Lab Podcast,where we discuss sciencefor everyday life.I'm Andrew Huberman,and I'm a professor ofat Stanford School of Medicine.Today we are talkingand more specifically themeaning how our body heats upfrom both the outside and the inside.Heat is a remarkable stimulus,meaning when we are in a hot environment,it has a profound effect on our biology.And heating up from the outside,or as you'll soon learn, from the inside,has a profound effect onof our health, including our metabolism,both in the immediate and long term;our cognition, meaningmore or less clearly.And if you're immediatelymakes you less capable ofHeat applied properly as a stimuluscan engage certain neurochemical systemsin your brain and bodythat can allow your brainWe will talk about those data today.So we're going to talk aboutthe science of heat and heating,both in terms of their mechanisms.And, as I know many ofthe tools related to the use of heat,things like sauna, how often to do sauna,how long to be in the sauna,how hot to be in the saunafor particular goals and outcomes.We're also going to talk aboutaround local heating.That is the use of heat appliedto specific areas of theor improve tissues at thatas well as your biologyIn fact, we are going to talk about onevery recently published paperthat came out in the journal Cell.Cell is one of the three apex journals,meaning three of the most competitive,most rigorous scientific journals.Those are Nature, Science, and Cell.This particular paperand I will go into itbut basically what this paper showsis that by locallyyou can change the identityat that location and elsewhere.We have three kinds of fat,white fat, beige fat, and brown fat.And as you will learn more about soon,white fat is not veryIt's more of a fuel reserve.It's what we typicallyBeige fat and brown fatand those mitochondriaor heating mechanism for your entire bodyand increase your metabolismand the burning of white fat.So in other words,having more beige fat andAnd it turns out thatof heat to specific areas of your bodycan increase the conversionIn other words, turn aninto a metabolically active tissuethat can help you burn off more white fat.I think many people are goingand the tools that emerge from this paper.It's a fascinating set of findingsthat actually emergedof the biology of burn andAnd that is not what I'mas a tool, of course,but understanding aimpact our biology and healthhas allowed these pioneering researchersto develop new tools to combatobesity and metabolic disorders,and that you can apply forI'm pleased to announce thatis now partnered withOur motivation foris to provide people one locationwhere they can go to accessin the specific dosagesby the scientific researchand that are discussedof the Huberman Lab Podcast.If you go to livemomentous.com/huberman,you'll see those formulations.I should mention that we arein the months to come,and you'll see specific suggestionsabout how best to take those supplements,meaning what dosages and times of day,and in fact, how towith specific behavioral protocolsthat have been discussed on the podcastand are science supportedin order to drive the maximum benefitfrom those supplements.And many of you will probablythat Momentous ships not justbut also internationally.So once again, if you go toyou will find what we firmly believe to bethe best quality supplementsin the precise dosagesfor taking those supplements,along with the ideal behavioral protocolsto combine with thoseI'm pleased to announcethat I am hosting twoThe first live event will take placein Seattle, Washington on May 17th.The second live event will take placein Portland, Oregon on May 18th.Both are part of a lecture series entitledThe Brain Body Contract,during which I will talk about scienceand science-based tools,many of which overlap with the topicscovered on the Huberman Lab Podcast,but most of which will notand will be completelynever discussed publicly before.Both live events will also includea question and answer period,during which you, the audience,can ask me questions directlyabout any aspect of scienceand I will attempt to answer them.Tickets for the two events, again,Seattle on May 17th andare both available atBefore we begin, I'd like tois separate from my teachingIt is however part of my desire and effortto bring zero cost to consumer informationabout science and science-related toolsto the general public.In keeping with that theme,I'd like to thank theOur first sponsor is LMNT.LMNT is an electrolyte drinkthat has everything you needand none of what youIt has electrolytes, andare sodium, potassium, and magnesium,which you need in the proper ratiosin order for your brain andLMNT was designed toof electrolytes in order to optimizemental and physical performance.People out there withof course, should be cautiousabout increasing their sodium intake.But many people can actually benefitfrom increasing their sodium intake,both for health and for performance.LMNT contains a science-backedof 1000 milligrams.That's one gram of sodium,200 milligrams of potassium,I consume LMNT when I firstduring exercise, and after exercise,and sometimes again, if I'vefor instance, after doing a saunaor taking a run on a hotIf you'd like to try LMNT,you can go to drinklmnt,to claim a free LMNT sample pack.You only cover the cost of shipping.Again, that's drinklmnt, lmnt.com/hubermanto claim a free sample pack.Today's episode is alsoInsideTracker is athat analyzes data from your blood and DNAto help you better understand your bodyand help you reach your health goals.I've long been a believer infor the simple reasonthat impact your immediatecan only be analyzed fromThere are a lot of bloodbut a major issue with many of themis that you get numbers backmetabolic factors, lipids, et cetera,but you don't know what toInsideTracker has solved that problemby creating a personalized dashboard.So you take your bloodyou get the results back,and where certain valuesfor your preference you can click on that,and it will direct younutrition, and supplementation, et cetera,that can help you bring thosethat are ideal for you.So it not only gives you informationabout where your health stands,it gives you directives as toIf you'd like to try InsideTracker,go to insidetracker.com/hubermanto get 20% off any ofthat's insidetracker.com/hubermanToday's episode is alsoROKA makes eyeglasses and sunglassesthat are of the absolute highest quality.I've spent a lifetimeand I can tell you that your visual systemis incredibly sophisticated.It allows you to do things likemove from a shady area outsideand to adjust your visual systemso you don't even notice that transition.A lot of sunglasses andwith those sorts of biologicalROKA sunglasses andEvery one of their glasses is designedwith the biology of theFirst of all, they'reso you don't even noticeSecond of all,they were designed to belike running and cycling, et cetera,and they won't slip off yourAnd they have a terrific aesthetic.So even though theyas active eyewear, they look great.So you can wear them out to dinner,to school, at work, et cetera.If you'd like to try ROKAyou can go to ROKA, that's roka.com,and enter the code Huberman toAgain, that's ROKA, roka.com,and enter the code Huberman at checkout.Okay, let's talk about heat,more specifically, let's talk aboutthe biology of heat and heatingand the health benefits and toolsrelated to heat and heating.The first question that we have to answeris how do we heat up?And the answer to that questionWe heat up from the outside,meaning the things thatthe clothing that we put on our body,whether or not there's heat in the room,or whether or not it's coldand we heat up from the inside.Our body has the capacityor to cool down, meaning toand it can do that in waysthat match the external environment.The simplest way to think about thisis that we actually havePeople will say, "Oh,"98.6."That's actually not true.Body temperature variesIt varies across time ofAnd at every point acrossyou have two distinct temperatures.One is the temperature on your skin,what scientists call your shell,and the temperature of your core,your viscera, meaning your organs,your nervous system, and your spinal cord.And as you can imagine,the temperature of your coreis always higher than theSo the important thing to knowis that you have aand a temperature at your core.Now you don't need to know exactlywhat those temperatures are in most cases,but it is vitally important to understandthat you have those two temperaturesand that your brain is constantlysending out signals to your bodyas to whether or not itdepending on the temperature of the shell,which makes total sense.This is a lot like a thermostat in a room,which is essentially paying attentionto how cold or hot it is,and then sending signals toto either heat up the environmentor cool down the environment,depending on the temperatureYour brain has neurons that send signalsto other cells in your bodyand deploy the release ofto heat you up when you are too coldand to cool you down when you are too hot.So, if you can understandthat you have two body temperatures,one at your shell, the surface,and one at your core, inside,and that your body andto balance those two temperatureswell then you're halfway thereto understanding the biologyof thermal regulation and heating,and you'll be a lot further alongin understanding howto improve metabolism orIn fact, later you will learnthat one way that you can heat upis by cooling down theThat's right.If I were to throw a coldonto your torso right now and ask you,"Well, how do you feel?"You'd say, "Oh, that'sHowever, because your brain is acting likea bit of a thermostat as the surface,the shell of your body felt cool,it would make sense that that thermostatwould activate biological mechanismsthat would heat up your core.Similarly, if I were to put youyou'd say, "Oh, wow, it'sbut your brain and your body would gothrough a lot of effortto cool you down.So anytime we're talking about heat,meaning deliberate heatit's very important tohow hot something is, how longbut the effect that has onIf you can understand thatthat are literally perfect for your goals.And as a final point about this,if you want to develop the best tools,leveraging heat for your biologyyou want to understand heat as a process,as a verb, as heating, not just heat,because there's thebefore you encounter the heat stimulus,before you get in the sauna, for instance,during the heat stimulus, soand then afterward.Everything in biology is a process.So as you'll soon learn,there is a specific saunacan allow anybody, in fact,to increase the amount of growth hormonereleased into theirThat's right, 16 fold.However, it involves shiftingto a cool environment,to a cool environment, overover a very short period of time,because it engages a switch, a process,that compounds, it builds on itself,to increase growth hormoneIn fact, if you were tofor a very long period of timeto match the exact temperatureyou would not experience thoseIt really is the transitionbetween hot and cool temperaturesthat engage the process of heatingand reheating over and over again.So, today you're going toYou're going to learn about thefor health and optimization,not just for growth hormone,but also metabolic health,even to impact mentalAnd in order to do that,you need to understand aof how you heat up and how you cool down,where the cells and circuitshow those cells and circuits work.I promise to make the description of thatwhich follows very clear,even if you don't haveAnd once you have that in hand,along with the understanding you now haveabout the fact that youand you need to think aboutwell, then you will be into use sauna or hot tub or other tools,even just a hot shower,as a powerful stimulusNow, the science of heat and heatingand cold and cooling, for that matter,goes back well over a hundred years.In fact, it's kind of amusing to methat nowadays there's ain the use of heat and coldand the science of heat and cold,because this was theas an undergraduate.And in fact, I did my graduateAnd at the time, thermalone of the hot topics in neuroscience.People were more focused on thingslike memory and consciousness.And of course those topicsto many people in many laboratories,but thermal regulation was consideredmore a thing for the physiologists.Nowadays, not just on social media,not just in the landscapebut in the landscape ofin the general ethospeople are reallyAnd the reason they're sois that a lot of the science has been doneboth in animal modelsand translates immediately toNow, a brief warning now andanytime you're talkingyou need to be very cautious,because unlike cooling down,where you have a fairly broadthat you can go into beforewell, you don't get to heat upbefore you start getting intoand neuron's in thethe brain and spinal cord,once they're damaged they don't come back.So hyperthermia is aLater I'll talk about waysto rapidly protect against hyperthermia,but I do want to give everybodyObviously, if you're pregnant, nursing,if you're very sensitiveyou want to stay out of saunasI'm sure there are exceptions to that.You definitely have to talk to your doctorif you're going to violate that rule.And for everybody, you want to approachany kind of tool relatedYou always have the opportunityto increase the temperature later.So proceed with caution.Be smart about it.I don't just say of that to protect me.I say that also to protect you.So now let's talk aboutwhat are the circuits for heating up?How does that happen?Many of you have probablyHow does that happen?What happens when you goand you're shivering,but you put on a coatWhat's really going on there?Well, there's a very basic circuit,meaning neurons that exist in the skin,in the brain, and in the bodythat communicate with oneto heat up if you need toI'm going to throw aa few new words at you.You don't need to memorizeactually you need to memorize one acronym,but it's very easy.It's called the POA.If you remember POA,you'll be home free forbut I know that there areand people interested in gettinga little bit deeper mechanism.And I do think it's importantbecause once you stand this circuitand the way it's structured,then you are going to be in arelated to heating.So here's how this circuit is structured.You have this shell,and within the skin youThose nerve cells haveThey're called trip channels.There's some other ones as well,which basically sense changes in heat.So if I were to put a hotor for instance,if I were to put a hotand then remove that hot object,those neurons would respond to that.They would send electricalAnd that's where the nextIn your spinal cord you gotthat exists at the topcalled the dorsal horn.The name, again, doesn't matter.And those neurons specificallyup to another area of your brain.Now here's where we getIt's the lateral parabrachial area.You don't need to knowbut it's a relay station.The lateral parabrachial areasends electrical signals to the POA.And I would like you to know POA.The POA stands for preoptic area.Neurons in the preoptic areabasically reside overThese are neurons within the hypothalamus,and neurons in the preoptic areahave the ability to send signalsout to the rest of your brain and bodyto get you to heat up andso that you heat up.That's right.If neurons in the preoptic areareceive an electrical signalthrough the circuit I just described,that goes from skin to dorsalto lateral parabrachial,they will start sending signalsout to the organs of your bodyto get those organs andAnd believe it or not, yourwill actually change the waythat you think and feel immediately.For instance, if somethingor something very hot contacts your skin,the preoptic area will send signalsout to the endothelial cells,the blood vessels boththat get them to dilate,to essentially increase theirin order to cast off heat.You will also start sweating.That sweating response is initiated,not by the hot day or the hot sun,but by the preoptic area neuronsthat send signals out to what's calledthe periphery of yourand other chemicals are released,things like acetylcholine,And if you happen to be shivering,neurons in the preoptic areawill make sure that you stop shivering.You're probably familiar with the feelingof being somewhat lethargic,or spreading out your limbs on a hot day.Well, that is the result ofimpacting your musculatureto get you to increase your surface areaso you can sweat off or release more heat.So there are all theseby which we dump heat.Some of those are purely physiological,below our conscious control,things like sweating,which you can't just makeMaybe you can through abut you can't just make yourself sweat.That is autonomic, it'sThings like vasodilation,the dilation of your veins in particularand capillaries in particular.These sorts of things.And, of course, theresomewhat voluntaryAnd the lethargy, the kindon a really hot day,that's also controlled by the circuitthat I just described.In fact, I just got back fromand it was remarkable toin the afternoons.I just felt like a total slug.I just could not moveexcept if I waited until the evening,even though it was later in the day,even though I hadn't napped,as the temperature in myas my body temperature cooled off,I felt like I had more energy.I was actually waking up,even though I had been awake for longer.So the relationship betweenis a very intimate one.If we're warm enough, we feel activeand like we want to move around.If we're too warm,we feel like we need to stay putand spread out our limbs and dump heat.And that brings me to aabout how we dump heat versusMany of you know, of course,Other mechanisms as well,but that's our main way of dumping heat.Other animals like dogs don'tat least not very much,so they pant in order to dump heat.And still other animals, like rodents,when they get too hotand they rub that spit onwhich might sound kind of gross,and probably will get you to think twicebefore petting any of those animalsor holding any of those animals again,unless that's your thing.Now, one other key thing to understandabout this circuit related to heatis that the preoptic areaalso can send electricala brain area that is often talked aboutin the context of fear,but is really just a brain areathat can activate yourThe sympathetic nervous systemis part of your autonomic nervous systemand is the one associatedor with the stress response,or even just the excited response.The sympathetic nervous systemwhen you're reallyThe preoptic area has the opportunityto trigger the activation of the amygdala.Now, it doesn't do itAnd it tends to do thatin an environment that feels too hot,that you feel is risky levels of hot.If you ever have gotten into a saunathat was very, very hot,you sit there for a minute.You'll notice that yourand there are reasons for that,and we'll talk about some ofin a few minutes, butYou may not feel like yourbut you often will feelespecially if you stay inThat impulse is the consequencecommunicating with your amygdala saying,"Hey, this environment is really hot,and I'm tryin' to cool down,and it's not really working.I'm dumping heat, butthe core of my body temperaturein ways that are goingAnd so it's a signal that you probablyshouldn't stay in thatNow later we'll talk about the advantageof pushing yourself a little bit throughsome of these very hot environments,provided you can do it safely,but the impulse to get yourselfout of a very hot environmentis the consequence of the POAcommunicating with your amygdala,and the amygdala then, in turn,activating your adrenal glands,which sit right above your kidneys,the release of adrenaline,and this feeling of agitationUsually you want to move outyou happen to be in.So now you know the circuit.Again, it's simple.It goes from skin to spinal cord,one brain area to another brain area.That's the key one in this discussion,which is the POA, the preoptic area.And then the preop area can kick offa bunch of autonomicwhich make us attempt to get cooler,things like sweating,and it can kick off behavioral responses,spreading out our limbs in an attemptto dump even more heat;feeling lethargic, so a lackand it also has thea mild, or maybe not so mild,panic response to get usIf you can conceptualize that circuit,or if you can even justeven at a top contour level,you're going to be in a great positionto understand the rest of the informationand the tools that follow.Next, I'd like to talk about the useof deliberate heatbut other tools as well,as a way to understand how heatand heating changes our biology.So, you're going to learn some mechanismand you're going to learn some tools.But first I'd like to just emphasizethat the use of deliberate heat exposurecan be a very powerful way toThere's a wonderful study on thisthat was published in 2018 that includesa lot of data from a lot of participants,in a lot of different conditions,for instance, peopleversus two to three times a weekversus four to sevenand compares all those.The title of the study isWith Reduced Cardiovascular Mortalityand Improves Riska Prospective Cohort Study.This is one of several papersthat regular use of sauna or other formsof deliberate heat exposurecan reduce mortality tobut also to other events,things like stroke and other thingsthat basically can kill us.What I like so much aboutand yes, I will provide a linkis that they involveSo for instance, in this particular paper,which was published in BMC Medicine,they looked at a samplewho had a mean age of 63,but there was a range of ages around 63,and of whom 51.4% were women.The rest were men.So it's a pretty nicely varied studyin terms of the populationsAnd basically what they foundwas the more often that people do sauna,the better their health isand the lower the likelihood they will diefrom some sort of cardiovascular event.What do we mean by sauna?We need to define some ofand I promise to provideto access some of the health benefitsthat were observed inwithout the need to have a sauna,'cause I do realize that a lot of peopledon't have access to sauna.First off, the temperaturein this and pretty much all the studiesthat I'm going to talk about,unless I say otherwise, aremeaning 176 degrees Fahrenheit,and 100 degrees Celsius,meaning 212 degrees Fahrenheit.So somewhere in that range.How hot should you make thethat you get into should youWell, that will depend onhow heat adapted you are.Yes, some people are betterAnd over time we allMeaning if you go intoyou become a better sweater,but the verb sweater,you get better at sweating,at dumping heat through the loss of water.So it's going to depend.I recommend starting on the lower endof the temperature scale,and if that's too hot for youthat you even lower theNow, how long were peopleto these hot environments?Anywhere from five toAnd as you'll soon learn,very brief periods of justcan be a powerful stimulusif the heat exposure is20 minutes can also be beneficial,but 80 to 100 degrees Celsius,meaning 176 degrees Fahrenheitis the general range thatIn this particular study,they compared the effects of peoplethat did sauna once a week,two or three times per week,or four to seven times per week.And what they saw was really remarkable.What they observed was that peoplewho went into the saunawere 27% less likely to diethan people that went intoagain at the temperature levelsand the duration thatAnd as you can imagine, the duration,the temperature levels were related.So if people went intothat were really uncomfortable for them,maybe they only went in for five minutes.Whereas, if they were morein a given environment orwas just simply higherwell then they tended to stay in longer.We can take a sort of averageof this five to 20 minute range,and today we're mainly goingbetween 10 and 20 minutesagain, 80 degrees and 100 degrees Celsius,176 degrees Fahrenheit,So these data point to thetwo or three times perand can lower mortalityAnd in fact, the benefitsfor people that we're going into the saunafour to seven times per week.Those people were 50% less likely to dieof a cardiovascular eventcompared to people thatjust once a week.So these are reallyencouraging studies.Certainly they caughtto start using deliberate heatWhat's particularly nice about this study,and the related study that, again,is linked in the show notes,is that they looked at a numberof potentially confounding variables,things like whether or not people smoked,things like whether or notwhether or not they tendedand they were able toSo the percentages that27% less likely to diefor those that went in theand 50% less likely to diefor those that went into theas compared to just once a week.Those effects really do seem to bethe consequence of the sauna exposureand not some other effectthat's correlated with sauna exposure,like going to the gym where peopleare working out seven times a weekand then also happenor quitting smokingthey adopt a sauna protocol,And now there have beenof the use of sauna for improving health,or I should say for offsetting mortality,that have found thatin cardiovascular events,but so called all-cause mortality.This is kind of medicalhow likely are you or somebody to diefrom a cardiovascular event,but maybe be also from some other event,some other health-related event,like cancer or something of that sort.And in every case,regular exposure to sauna startingat about two or three times per week,all the way up to seven times per week,greatly improves,meaning statistically significantin the sense that people are less likelyto die of cardiovascular eventsand other things that kill us.So I and many other peoplewho are interested notbut in educating aboutto the general public,But knowing what we know aboutit probably shouldn't surprise usthat this sauna type exposureor deliberate heat exposureSo before we get intoof how heat can have all theseI want to just talk aboutand emphasize that youin order to get these benefits.It is simply a matter ofand your core heat up properly a bit,not too much, not too little,but that you heat those up.And no, you do not need toor place a thermometer into your core.In laboratory studies and in humans,if you really want to knowbasically you try andas close to the core as you can.So typically that's doneor even up the nose.You don't need to do any of that.This isn't a laboratory study.There are ways to create a hot environmentsuch that you heat up yourwithout having to measure yourIf you want to do that, be my guess,but I'm not going to provide a protocol.So the question is, how are youAnd I realize that there are dry saunas,there are steam saunas,there are hot tubs,and there are simply roomsThere are also ways in which you canincrease your shell andby moving around a lotand doing that wearing a lot of clothing.There's nothing special aboutany one of these approaches or protocols.It just so happens that saunais one of the moreAnd certainly for the studiesnot just the ones I referenced before,but all the studies that I researchedlooking at this episode,it makes sense why they would use sauna,because it's very hard, for instance,to create conditions where you havefive people go out jogging,wearing heavy sweaters and hats,wool hats on the middle of summer,it's very hard to set up those conditionsin a way that's controlled for everybody.Whereas, it's pretty straightforwardto have a sauna where you haveone or several people just get intothat one uniformly hot environment.That's a much easier study to run.So just to be clear, theYou want to get between 80Now you know the conversion to Fahrenheit.You could, however, immerse yourselfin a hot tub or hot waterThat's another way to approach it.If you didn't have accessyou could also put on a hoodieor you could do like the wrestlers do,and you could actually buyThey're literally called plasticsthat wrestlers or other athletesthat wish to drop water weight will wear,and then go jogging in that.All of those will increase your shelland your core body temperature.Especially if you do it on a hot day,but of course be careful,Don't become excessively hyperthermic,'cause you can get heat strokeBut if you're going to use sauna,often I get the questionWell now you know.How long should you be in there?Five to 20 minutes per session.Although, I will talkto optimize hormone output,in particular growth hormone output,by doing four very brief sessions.So maybe not a continuous session.We'll get into that in a few minutes.And, of course, you have to ask yourselfwet sauna, dry sauna.You know what?Doesn't matter.Use what you prefer.Many people ask me, "Well,We have an entire episodeand low level light therapy,It does have certain benefits for skinand other organs and tissuesMy understanding, orof most infrared saunas out thereis that they don't get hot enough.They don't get up to that 80Some do, most don't.So what you end up with is a situationwhere you've got a red light,low level light therapy stimulus,and you've got a saunaAnd there are a lot of ideas and claimsabout how they work togetherin order to get you improved benefits.I personally am of the stance,based on the literature that I've read,that you want to get into those rangesof 80 to 100 degrees Celsiusbefore you startyou're also going to includeSo there's nothing specialIt's really the temperature of the saunathat you happen to get into.So which tool?Which sauna?Which stimulus?Do you run wearing plasticsor do you get into a sauna?That's going to depend ayour budget, and what you haveThis is a lot like ourMost of the studies have lookedup to the neck,because that's a very controlled situationthat you can do in a laboratory.They have not exploredSo there's just less data,or walking around in a cold environment.But we'll talk a littlebecause as you'll soon learn,you're actually talkingSo what kind of mechanisms are activatedin your brain and bodythat allow for the various health benefitsof sauna or other formsWell, we talked about reduced riskof cardiovascular event related mortalityand all-cause mortality.As you'll soon learn,there are also tremendous benefitsin terms of increases in growth hormone,reductions in cortisol, et cetera.I will detail those.So what happens when you doWhat are the mechanismsthat allow for the variousWell, your shell, your skin, senses that.And through the circuitactivates neurons in thewhich in turn activates mechanismsin your autonomic nervousSo blood flow increases.Plasma volume of your blood increases,and stroke volume.The volume of blood that is mobilizedwith each beat of yourAnd your heart rate increasesto anywhere between 100That general constellation of effectslooks a lot like cardiovascular exercise.And in fact, for all intents and purposes,it really is cardiovascular exercise,except that there isn't the mobilizationand the loading of joints andAnd of course thereof cardiovascular exercisethat relate to impact on the ground,improvements in bone density,But basically your heart starts beating,more blood starts circulating,your vasculature changes shape, literally,to accommodate those increasesin heart rate and blood volume.And you're basically gettingin that hot environment, evenAnother set of positive effectsrelated to being in these hot environmentsare hormone effects,shifts in the output of hormones,both from or your adrenalsand possibly from the testes and ovariesand even within the brain.One of the more striking examples of thatcomes from a study thatThe title of the study is"Endocrine Effects of"and Cold Water ImmersionAnd indeed, this study was, inI'll just briefly describeThey had these men attendof 12 minutes each.So again, well within that12 minutes.The temperature of those saunaswas 90 to 91 degrees Celsius.So I'll just quickly do the calculation,admittedly, not in my head.That's 194 degrees Fahrenheit,Afterwards they had aduring which they didor cold water of about10 degrees Celsius isAnd then they measuredthroughout this study,They looked at testosterone,they looked at DHEA, whichThey looked at prolactinThe significant effects of the protocolthat I just described were on cortisol,a so-called stress hormone.So-called because whenfor long periods of time,cortisol levels tend toBut I should point out that aright about the time of waking,and specifically rightis actually beneficial forSo having some increasingis a good thing, providedLate day increases in cortisolare associated with depression.That's been shown by studiesThe major effect of this studyis a significant decreasein these subjects.I think this is reallybecause many people suffer from acute,meaning immediate, and longterm stress,and are looking for waysControlling your cortisol is tricky.In the episode on stress,I talked about supplementsthat can be used to limit cortisol,but you have to be carefulfor extended periods of time,meaning for longer than two weeks,because you can get into other issues.I talk about breath work protocolsthat can allow you to clamp or reducethe stress response in real time.Again, see that episode for those,but many people are overworked.They're overstressed.They're, for one reason or another,they're subjected toor their level of stressto keep their cortisol levelsSo the protocol I describedto 90 degree environment,that's again, 90 degree Celsius,followed by a six-minute cool down breakin cool water, 50 degreesI can imagine that you couldor a cold shower afterwards,that had a very significantSo there you have a toolthat's not a completely zero cost tool,'cause you need to heat the waterand you need to have accessat least hot and coldbut it's fairly minimalEspecially if you start getting creativeabout maybe taking a 12-minute jogwearing a lot of clothing if it's hot out,then getting into a cool shower.You might not get the same extremeor significant reduction in cortisolthat was observed here withbut it's likely that you would geta similar result over all.Now, I mentioned they didand I'll just tell youthat they did not see significantprolactin, DHEA, et cetera,As you'll soon see, therethat can impact those other hormones.So if you're seeking toI think this is a very interestingand potentially usefulAnd again, we will provideif you'd like to read more about the data.So that is one set ofand the related protocol.What about some of theWell, we'll talk about those,but I want to talk aboutof the underlying mechanisms,because if you understandyou can really tailor your sauna protocolsfor your particular needs.One of the more dramaticof going into a hot environmentis the activation of so-calledHeat shock proteins arein your brain and body to rescue proteinsthat would otherwise misfold.What do I mean by this?Well, most of you'reif you have protein in the kitchen,like a steak or a piece ofand you heat it up, itRaw meat is different than cooked meat,to be quite blunt about it.Heat changes the quality of proteins,not just in terms of how they taste,but the way in which they are configured.It changes it right downWhen your body goes throughand we'll talk about those changes,but in response to hotheat shock proteins areand prevent the changes in proteinsthat would be detrimental to your health.So at least in the short term,activating heat shockYou don't want heat shock proteinsto be activated for long periods of time,because that gets to beBut these heat shock proteins,of which there are many varieties,basically have the job ofand making sure that cellsthat contain proteins that are misfoldingbecause they got heated upand they also, sort ofmaking sure that proteins within the cellsof your brain and body don'tAgain, I'm describing thisbut it's well established inthat sauna exposure of theactivates these heat shock proteins.There's some interestingin animal models that really nicelymechanistically support thein some of the benefits ofSome of these studies were done in flies,meaning Drosophila, fruit flies,'cause there are great model organism,because you can deleteOther studies have been done in mice.And now there are also studiesand I will talk about those.One of the more dramatic examplesthat's always touted in this fieldof deliberate heat exposureis that if they expose theseto 70 minutes of a heatobviously didn't kill them,but activated heat shock proteins,it could extend their life by 15%in a heat shock dependent way.Meaning if they made fliesthat didn't have thesewell then they didn't seeAnd this is one of the reasonsThis is not an experimentHowever, there have beenexamining some of theof deliberate heat exposurethat point to the mechanismsby which deliberate heat exposurecan help protect againstimprove overall, and possibly,and I want to highlight possibly,possibly extend life.One such mechanisminvolving a molecule called FOXO3.FOXO3 is a very interesting molecule,because it's involvedDNA repair is part of theWe'd all like to think that we're born,and based on the genes we have,we are healthy, healthy, healthy,then eventually we age and then we die.But from the time we'rethere's a constant repairin a modification of the genespuberty being the most dramatic example.You see a kid beforelooks like a different kid,sounds like a different kid,In fact, it basically isIt's not just the hormones.It's that hormonesto turn on and turn off certain genes,literally convertingin the brain and body to doSo it's not just the sproutingof new aspects of our biology.It's literally the conversionfrom one function to another.That's puberty.And we'll do a wholeWe actually did an episodethat talks a little bitBut the point is thatgenes are being turned on,Genes are being turned on.Gene are being turned off.And DNA, the stuff of genes,FOXO3 sits upstream in aand again, clearing ofSauna exposure,in particular saunaor ideally four to seven times per weekin that 80 to 100 degree Celsius rangehas been shown toFOXO3 in turn upregulatesand clearing out of thesewhich is known to be importantfor various aspects ofand other aspects of maintaining health.So these are the likelyfor the improvements in lifespan,or rather, I should say,these are the biological mechanismsthat apparently offset someand other forms of mortalityOne especially interestingthere are individuals out therethat have eitheror who have versions ofso to speak,those people tend to beto live to 100 years of age or longer.So these are people thatand fortunately for them,more clearance of senescent cells,more DNA repair, et cetera.For the rest of us, atI don't have one of theseRemember, mutations can be beneficialor they can be detrimental.This, if your goal is to live longer,is a beneficial mutation.If you don't have these FOXO3 mutationsthat allow you to be a centenarianat 2.7 times high ordeliberate heat exposure is one waythat you can increase FOXO3 activity.At this point in time,meaning when looking atit isn't clear what theis going to be, specificallyand that's probablyThere is no sauna protocoldesigned specifically to reduce cortisolor specifically to increase FOXO3or specifically to activateAny deliberate heat exposureis likely to impact allAgain, I encourage you to use this guideof 80 to 100 degrees Celsiusas your kind of bookendsand where you want to startin terms of deliberate heat exposure.And I would encourage you to usethat five to 20 minutesas your rough guide of howNow, there was a studythat was mainly focused onI detailed this quite extensivelyThis is the beautifulAnd that study looked atbut also sauna exposure.And that study found that 57,yes, 57 minutes per week of sauna exposurein conjunction with 11of deliberate cold exposurewas the threshold for getting improvementsin metabolism and increases in brown fat,this very active fat tissuethat improves mitochondrialmeaning heating of the body.We'll talk more about brown fat later.Why do I mention this?Well, for those of you that are interestedin increasing metabolism,it does seem to be most beneficialto do that 11 minutes perdivided up across two or more sessions.So it's not 11 minutes all at once,but shorter sessions,and to get 57 minutes minimum per weekof sauna exposure, again,in the temperature rangesAnd again, it's not 57 minutesThat's 57 minutes total perSo you might divide that intoAnd again, I don't thinkIt could be 60, it could be 64.It probably could be 55.Remember your biological systemsare not counting thingssecond by second, least not in most cases.So for those of you that are interestedin improving metabolism,or just take the Søbergwhich is 11 minutes total perbut safe, cold exposure.So uncomfortably cold meansyou really, really wantor the ice bath or whatever environment,but you can stay in,11 minutes total per weekand then 57 minutes per week, or so,of deliberate heat exposure,again, uncomfortably,but uncomfortably hot, excuse me,but safe to stay in,probably divided up acrossOkay, so we've talkedto decrease cortisol.We've talked about the use of saunato increase heat shock proteins.We've talked about the use of saunato increase FOXO3.Now I'd like to talkto increase growth hormone.Growth hormone is a hormonethat we all naturallywhich also resides nearThe signal for the pituitaryarrives from neurons thatSo growth hormone releasing hormones,believe it or not, that'sstimulate the release of growth hormonefrom the anterior pituitary glandinto the general circulation,and then growth hormoneof cells and tissues of the body.It is responsible forAnd the growth spurtthat everyone experiences during pubertyis the consequence of growth hormone.What I'm about to describe is a studythat found dramatic, reallyincreases in growth hormone,but I also want to emphasizein growth hormone were not of the sortthat are observed in puberty or in infantsbecoming adolescents orThose levels of growthwith those massiveof body morphology, of shape,are far greater than the sortsAnd yet, as all of us age,when we go from adolescenceand then into a young adulthood,but then starting in our early 30s or so,the amount of growthis greatly diminished.Normally we would releaseafter we go to sleep,in particular in thewhen our sleep is comprisedAs we age, less growth hormone is releasedduring that slow wave sleep.There are various thingsthat can promote theand we will talk aboutin a moment, things like low blood sugar,turns out, is a stimulusAnd I don't mean hypoglycemia of the sortthat makes you dizzy and want to pass out.That's bad.I mean, not having highin your bloodstream.This is one of the reasons why many peopleare drawn to intermittent fastingit's because of the reportedI'll touch on those briefly,but if you want to learn more about thoseand what their real impact isand the extent of growth hormone,check out the episode I did on fasting.You can find that at hubermanlab.com.Certain forms of exerciseto stimulate growth hormone release.And in a few moments,I'll talk about how exerciseor how heat can be combined with exerciseor certain patterns of food intaketo further increase growth hormone.But before I do that,I want to review some of the data,and one study in particular,that discovered certain formsusing sauna can stimulatein growth hormone output,which for people in theircould be very useful,and may also be useful for peoplewho are just trying to stimulatethe release of more growth hormonein order to, for instance,or stimulate fat loss orof a particular injury.The title of this paperis "Endocrine Effects ofAnd this is a paper thatwhich is some years ago,but nonetheless serves as a basisfor a lot of other studies that followed.So let me describe whatThey used an 80 degreeso that's 176 degrees Fahrenheit,and they had subjects dofour times per day.So that's two hours total in one day,30 minutes in the sauna, a30 minutes in the sauna again,cool down rest, a third,So, two hours total in thisSo that's a lot,but what they observed wasSo they had subjects do this protocol,and I should mention they hadin this study,and the entire study lasted a week.They did this two hours ofday three, and day seven of that week.And they measured a lotcortisol, thyroid stimulating hormone,thyroid hormone itself,luteinizing hormone, andwhich are hormones that essentially drivethe production of other hormones.We won't get into that too deeply,but if you'd like to learn about FSH,follicle stimulating hormone,please see the episode on optimizingtestosterone and estrogenThey looked at prolactin andI'll just cut to the chaseand tell you the effectsIn subjects that did this two hour a day,80 degree Celsius protocolexperienced 16-foldSo they measured growth hormonebefore the sauna and after the saunaand growth hormone levels went up 16 fold,which is obviously an enormous,and it turns out statisticallyNow, one important caveat here.Remember earlier when I talked aboutpeople who did sauna once a weekversus two to three times a weekversus four to seven times a week,and the more often people did sauna,the less likely they were toor other things of that sort?Well, in this case,the effects of saunaactually went down the more oftenthat people did thisSo as I mentioned,they did this two hour a daydivided into 30 minute sessions protocolon day one, day three,And what they found was on day one,there was a 16-foldOn day three, however,there was still a significantas compared to before sauna,but that effect wasSo now instead of gettingit was more like a threewhich is still a huge increase,but not as great as theAnd then on day seven, there tended to bea two, maybe a threefold increase,but not as great as theWhat does this mean?And why does this happen?Well, the reason thisjust like cold, is a shockIn the context of cold,if you get into a very cold ice bath,for instance, a five-degreeit's known to increaseIt can double the amount of norepinephrinethat you suddenly releasewhich actually can haveI'll talk about those in a little bit,but if you were to do that every day,you would become cold adapted.This circuit that compareswould adjust in ways thatthat cold stimulus,or more likely to createin preparation for that cold exposure.This is why, for instance,people that use deliberate cold exposureto try and increaseoftentimes will get results for a while,but then if they're doing it a lot, a lot,they stop getting those effects.I talk a lot aboutif that's your goal,but similar mechanisms are at play here.So we have to imagine thatwhen the subjects gotwhatever pathways wentfrom measurement ofto changes in temperature at the coreled to these big increaseswhich is basically a way ofI already told you before.But the fact that thateither means that thein communicating that shift in temperatureor that that shift inbecause the downstream effectorswere not engaged to the same extentbecause it wasn't as much of a shock.And I think the latterThis is very much akin to weight trainingor cardiovascular exercise,where if you run up a hilland your lungs are burningand you're heaving and breathing hard,on the first day, that'sBut if you do it everyprovided you allow yourself to recover,pretty soon you're running up that hilland you're not breathing as hard.There isn't as muchet cetera, et cetera.Your body adapts.So, one of the key things to understandabout the use of deliberate heat exposureis if you're going to use itin order to try andin growth hormone,you're going to need to be careful aboutnot doing it more than,Now, I'm extrapolating from this study.Maybe once every 10 daysbut if you start getting heat adapted,it's very unlikely thatthese massive increases in growth hormone.So I don't mean to be discouragingof using deliberate heat exposureto access growth hormone increases,but if that's your specificthen I think it's reasonable to saythat you don't want to doat least not of the sortmore than once a week, orand that you would want to time thatto other events in youror if you are trying to pushor simply in order to accessmaybe three times per monthIf you start doing deliberateyou'll still get increasesbut they are not goingas the increases in growth hormonethat you're going to experiencewith deliberate heat exposureAn important way to frame thisis actually in the context of cold.And while you might say, wait,this is an episode on heatyou really can't have awithout talking about cold.Because, as I mentioned earlier,if you cool the outsideyou're actually heating up your body.In fact, the circuits thatand that control cooling of the body,for instance, the activationor fat loss in responsethose are also controlledof the hypothalamus.So we can take a step backwhat it would take to designthe optimal protocol forby looking at cold,and here's what I mean.There have been beautiful studiesshowing that if people getfour degrees Celsius for 20 seconds.As I mentioned earlier,that will cause the a 200 to 300% increasein norepinephrine.Norepinephrine is alsoAnd norepinephrine and otherlike dopamine increased dramaticallyin this very brief cold water exposure.And those increases inare known to have long-lasting effectsthat generally lead to improvementsin mood, focus, and alertness.So they're pretty significant.However, they aren't significant enoughto increase metabolismWhereas, other studies have shownthat if people go outsidewith a proper amount,but a fairly minimum amount of clothing,you can experience even greaterBut the time that's required in orderto experience thosefor instance, 16 degrees Celsius.So if you have six hours a dayor if you can turn the air conditioning onin an environment and makeBut basically what I'm describing is thatyou can sort of bookend theYou can use a very briefin order to stimulate heat shock proteins,growth hormone, et cetera,or you can use longer exposurein less intense versions of heat and cold.You really have to findand what you can do safely.And if you're confusedplease use the parametersFirst of all, check with your doctor.As always, make sure that you're somebodywho can do deliberate coldbut that 80 to 100 degrees Celsius,meaning 176 degrees Fahrenheitthat I keep repeating over and over,'cause I know somebody's going to ask,even though I repeat it overI'm delighted to keep saying it,and to respond if someone asks again.Well, those parametersbookend what you should doin terms of the intensityHow long?Well, we heard earlier,Why not start with five andAnd then if you're feeling really boldand you really want towell, then you could dothat 30 minute fourevery once in a while.So you have to really figure outwhat you're using heat exposure for.This is one of the reasonsis it better to get in aWhat's the optimal temperature?Is it better to take a hot showeror a hot bath or a hot tub?To be completely honest,it depends on what you're goingwhether or not you wantand what your specific goals are.So the purpose of this episodeis really to arm you withand to arm you with the general parametersthat are going to allow youto access the results that you're seeking.For what it's worth, Iand I've been using athat involves trying,meaning I accomplishtrying to get into a saunafor three 20-minute sessions every week.I use a dry sauna, soIf I don't have access to it,I might take a hot bathBut in general,I just stick to doing theAnd I generally will doeither a cardiovascularor I will do it later in the evening.Why later in the evening?Well, it has to do with thethat we all experience.Talked a lot about thisand the episodes related to sleep.But in a nutshell, here's how it works.Every early morning,about two hours beforeyour body temperature isWe call that your temperature minimum.Right about waking yourIn fact, an increase in body temperatureis part of the reason you wake up at all,unless, of course,Increases in body temperatureare going to be one of the major thingsthat wakes up your brain and body.Body temperature will tend to continueto increase through the morning.You'll get that increase in cortisol.That's a healthy increase in cortisol.Body tempera will increaseand then we'll start toThis general contour can be shiftedby whether or not youbecause of the so-calledThat is, every time you eatin body temperature and metabolism,but it's not really that significantto throw off this generalbut toward the afternoonmost days, depending on time of year,your body temperature will peak,and then it will start to drop.And as your body temperatureand here I'm referring tonot your shell body temperature,you will start to get sleepyand to transition into sleepand to maintain sleepYour body temperature will remain lowuntil you hit that temperature minimum,and then it'll start to come up again.What that means is that when you decideto do sauna, or coldit's going to be important.Why?Well, as I mentioned earlier,if you were to make theat least in the immediateyour body temperature will increase.So for those of you that areand are still working on your sleep,remember sleep is the foundationof all mental and physicalyou should try to get really quality sleepof sufficient duration,That should be an ongoingfor a huge number of reasons.Watch the master sleep episodeif you'd like to hearand the mechanisms to makeBut in any event,cold exposure late in the eveningwill start to increase yourAnd that can make it hard forNow, if you're very, very tired,because you've been workingor both throughout the day,might not throw off your sleep so much.I've gone through boutswhere I'm just so, so busythat the only time I canor the cold shower is late in the eveningand I have no trouble sleeping after that.However, if you have trouble sleeping,I would recommend doing theto match that natural heating,that natural increase in body temperaturethat occurs across the 24-hourSimilarly, if you're going toyou'd be wise to do that later in the day.You'd be wise to do it later in the daybecause when you getsure, the surface of yourthe core of your body heats up,but then it also activatesthrough the preoptic area,and when you get out ofsauna or otherwise, your bodyAnd so many people findin the later half of the day,or even just before sleepand then take a warmish shower afterwards,then they find it easier to fall asleep.And that makes sensebecause their bodyAnd in fact, if yourthe maximum amount ofthat's also going to be theespecially if you haven't eatenin the two hours before sleep.So if you're really goingyou're really trying to optimize sleep,and the two things are actually linkedbecause of the release of growth hormonethat happens from the pituitarywell, then you would bemaybe once or maybe twice a weekin the evening or at nighttime,then taking a warm orjust enough to kind of rinse offand then get ready for sleep.And to do that, not necessarily fasted,but to try and keep your levelsof glucose and insulin somewhatThe reason I say that is thatand or insulin tends to bluntor reduce growth hormone release,and that's true for anyincluding exercise and including sauna.So there's a really nice study on thisthat I can point you to,is this study that wasLiterally, that's the name of the journal.I love it when journals have these nameslike Pain or Stress.I find that somewhat amusingbut nonetheless, amuse me.The title of this study is"to Different Consecutive"Is There Any Difference?"And I don't want to go intobecause it's prettybut basically what theydo sauna and then gave them a drugor a condition of having low,not dangerously low, but low blood sugar.Or they had them in a conditionwhere they had low bloodOr they had them do an exercise protocolthat led them to increased growth hormoneand then had them do low blood sugar.Basically mixing andthat could increase growth hormone.And what they found wasWhat they found was that doing sauna onceand then waiting some period of timeand then later that day doing sauna again,they didn't see the same increasein growth hormone both times.First they got a bigand then less if they did sauna again.If they had people dowhat they found was exercisebut then following it with saunadid not allow you to getIn general, anytime youyou reduce the likelihoodthat you're going tolater that day.And this partially explainswhere if people did this growthon day one, but then on day threethey didn't see quite as big an effect,and on day seven they didn'tAll it basically boils down to is thatif you really want to crank outthe most amount of growthdo it fasted or at leastin the two or three hours before.You don't have to be deep into a fast,and the whole notion of what breaks a fastis kind of an interesting conversation,because it's contextual.Will a sip of coffee break your fast?Well, maybe probably not.Will one grain of sugar break your fast?No.Will an entire candy bar break your fast?Yes, it has to do withwhen you ingest that particular food item.Not so much what thatBut the bottom line herethe most amount of growth hormone,wait a couple of hours after eatingbefore getting into the sauna,or maybe do it before dinnerDo the sauna before dinner, that is,then prepare dinner, then eat dinner,and then make sure thatbefore going to sleep.You're going to have to arrangeI know most people can'tjust to get growth hormone increases,nor do I think people should approachhealth protocols that way.I think for 90% of people 90% of the time,just getting into the sauna once or twiceor three times a week isfor the number of reasonsAnd you don't want to obsess too muchabout out the exact conditions you needin order to get the greatest effectout of that sauna treatment.These are just some additional tweaksrelated to food intakeand low level hypoglycemia and exercise,that if you wanted to leverage, you could.So if decreases in body temperaturetend to aid the transition of sleepand getting out of a hot saunatends to promote decreases in body,it makes sense why you would want to putyour sauna exposure or otherin the second half of your day,and maybe even right before sleep.Now, regardless of whator how frequently you do it,you're going to want to hydrateWhen you go in the sauna, you lose water,and when you lose water,you need to replace it.Why?Well, you need water for all your cells,but you also need electrolytes.So make sure that you'rethat you lose in the sauna.Now there's no exact formulaand whether or not you need electrolytesin that water or not.It's going to dependmeaning how heat adapted you are.It's going to depend on how much saltyou tend to excrete in your sweat.Huge amount of variation, but in general,one way to approach thisthat you drink at least 16 ounces of waterfor every 10 minutes that youYou could do that beforeyou could do it during andNow, there are other reasonsthat have nothing to donothing to do with growthbut rather have to do with improvementsin mood and mental health.In fact, the data related to saunaand other forms ofimproving mood are very impressive,both at the mechanistic leveland in terms of the longterm consequencesthat people experience.First of all, we need to ask,how is it that deliberate heat exposurecan improve our mood and wellbeing?Well, it turns out that itbut it also improves ourin response to things thatwould ordinarily makeNow, this is not a situationwhere you're going to be walkingin response to nothing at all,simply because you went in a sauna.What I'm talking about is themeaning chemical pathwaysthat allow you to experienceSo here's how this wholesauna, mood thing works.Many of you have probablyEndorphins are a category of moleculesthat are made naturallyand that are released in responseto different forms of stressors.That's right, in response to stressors.So, if ever you've gone out on a long run,and at some point in that run,you feel like you're achingor maybe you have shin splints,part of the reason that you experiencea lack of pain at some point, usually,or you experience a euphoriais the exercise-inducedOr rather, to be more specific,I should say theon the stress system,which in turn triggerIn other words,when we experience shortthe endorphin system is activated.Now the endorphin system isbelieve it or not.It also about feeling bad.And there are two generalThe first are the ones thatendorphins, things that bind for instanceto receptors like the mu opioid receptor.Opioids are not just prescribed compoundsor unfortunately drugs of abuse,which they are.We have this opioid crisisin the United States and elsewhere,which is a very serious and tragic thing,but we make endogenous opioids.We make endorphins thatand that make us feel mildly euphoric.We also make endorphinsthat's D-Y-N-O-R-P-H-I-N-E, dynorphine,that actually make us feelWhen we get into a hot sauna,or a hot environment of any kind,dynorphins are liberatedAnd I should mentionby many neurons in manySo you might think, well,Why would I want to releaseWell, first of all,when you get into anuncomfortably hot scenario, oh gosh,this is sounding terrible.And a deliberately hot environmentthat you are using to try and triggersome sort of biologicalI should say,the discomfort that you feel,the desire to get out of that environment,is in part the consequenceIt's also the consequenceof the activation of thatRemember, the preopticwith the amygdala and triggerthat kind of fight or flight mode,I want to get out of the sauna.This is really, really hot.But dynorphine is also liberatedfrom a certain number of neurons.Dynorphine binds to what'sThe CAPA receptor binds dynorphineand triggers pathwaysthat lead to agitation, to stress,and believe it or not toThis is why you want toand remember if it's unsafe levels of hot,then you should get out of that saunaor other hot environment.But if you're working in a rangeor you're exposing yourselfto a range of heat that's uncomfortable,but safe to be in,from these neurons, bindAnd as a downstream consequence of that,there will be an increase in the receptorsthat bind the other endorphins,the endorphins that make you feel soothed,that make you feel happy,and that make you feel mild euphoria.So there've been athat initially deliberate heat exposure,by sauna or otherwise,causes the release of dynorphine.In fact, I think it's fair to saythat every time we getinto a hot environmentor a cold environmentdynorphine is likely releasedand binding to the CAPA receptor.But over time that binding of dynorphineinto the CAPA receptorin the way that the feel good endorphins,things like endorphin bindingand there are still otherso to speak.That system becomes much more efficient,such that people feel an elevationin their baseline level of mood,and when a good orthey feel a heightenedor awe or improved moodThis is not unlike the effects of caffeineon the dopamine receptor thatAnd for those of you thatmany of you drink caffeine and love it.Part of the reason you love itis because of the releaselike norepinephrine, et cetera,the energy that it gives you.Maybe the taste, I would hope, as well,but caffeine ingestionin dopamine receptorIn other words, it allowsto work better so thatfor a given amount of dopamine release,you experience moreThis is a similar mechanism,but within the endorphin pathway.So what does it mean?It means that a little bit of discomfortas a consequence ofwhile in the short term,doesn't feel good, by definition,it is activating pathwaysthat are allowing the feelthat exist in your brain and bodyto increase their efficiency,placing you in a betterin response to the events of life.I confess I'm very excited about the dataon deliberate heat exposureand improvements in the chemical systemsthat underlie good mood.And just to underscore this further,the dynorphine system is notIn fact, there are beautifulout there about the role of dynorphinein stress and depression,in stress and alcoholism,just as a brief aside,and in the future weon alcohol and alcoholism,but turns out that chroniccauses changes in dopamine receptorsthat make it very difficult for peopleto achieve pleasure through thingsother than alcohol, and even alcohol.That's kind of the reallywhich is the thing thateventually is just requiredto maintain baseline levels of dopamine.And I've talked before,when she was a guest on this podcast,talked about the pleasure pain balancethat exists within the dopamine system.It is beautifully describedin her book "Dopamine Nation," by the way.Excellent book I recommend toWell, in that context of pleasure and painit's very clear what theIt's actually a moleculeand that's dopamine.The pain molecule, however,And the fact thatin stress and depression and alcoholismand the relationship betweenis something that we shouldAnd for that reason,I'm very excited about the factthat deliberate heat exposurecan leverage the dynorphine systemin a short term and an acute waythat allows mood to improveSo, for those of you thatkeep in mind that a lot ofon our biology relate to metabolism,cardiovascular function,And along those lines,again, published in 2018.I don't know why.I guess 2018 was a big yearfor deliberate heat exposure studies.The title of this study is "Sauna Bathing"and Risk of Psychotic Disorders."And this was a prospective cohort study.Again, we'll provide a link to this study.It's a really interesting studythat explored the relationshipso people suffering fromschizophrenia and otherand use of sauna.So essentially what this study didis they looked at a verymore than 2,000 subjects,who had no history of psychotic disorders.They were classified into three groupsbased on their frequency of sauna use,either once a week, two toor four to seven times per week.This should call toon all-risk mortality andAnd then they explored the hazard ratiofor psychosis specifically,meaning how likely it was that peoplewould develop psychotic symptomsor full blown psychotic illness,according to theirSo, again, this isn'tAnd according to the data in this study,what they concluded is thatthere was a strong and inversebetween frequent sauna bathingand the future risk of psychotic disordersin this population.Now, this does not mean that goinginto a sauna seven times per weekis going to prevent peoplefrom becoming schizophrenic, necessarily,or from having a psychoticAnd of course, frequent sauna use will berelated to otherBut in this study, asthey went to great lengths in order to tryand limit those so-calledNow, of course, this is just one study,and again, it's correlative, not causal,but based on the large numberplus the rigor of thewe're starting to see a general picturethat using the sorts of sauna protocolsthat I've describedfive to 20 minutes or so,done one to seven times per weekis associated with a general improvementin cardiovascular health,a general improvement in mental health,and it really points to the fact that,yes, sauna done acutely for30 minutes each sessionmaybe getting into cold bath,sure that can potentlybut done on a more regularimprove heart health,And for that reason, and theit is conceivable to come up with a waythat you could get intofor a minimum of cost.If it's a hot bath, orbundling up and going foror if you have access tothat we're really talking about a stimulusto initiate a large number ofthat wick out to improve multiple aspectsof brain and body health.So up until now, I've beenSo for instance, putting yourwhich of course is what most people do,or getting into a hot tubor in the cases where we were talkingabout deliberate cold exposure as a meansto increase core bodygetting into an ice bathup to your neck or intoNow I'd like to talk aboutspecific parts of the body,meaning certain surface areas of your bodyas a means to get effectsas well as at the whole body level.Numerous times throughout this episode,I've talked about theSo what should you do if youis hyperthermic, is too hot?Well, if you understand just a little bitabout the cooling and heating systemsof your shell and core,there are some terrificin order to cool off your core quickly.And remember the core consiststhe spinal cord, and the viscera,which are really the organsSo, being able to cool offcan be very beneficial,and in some cases, itThere is a way to moreand that's through specificmeaning particular skin surfaces.I've talked extensively aboutIt was also covered in the episodewith my guest, Dr. Craig Heller,from the Biology Department at Stanford.It relates to the so-calledon the upper half of our face,palms of our hands, andAnd for those of you thatI encourage you to continuebecause today I'm going to talk aboutspecifically how to heatthrough these glabrous skin surfaces.Very briefly, the mechanism is as follows.The palms of our hands,and the upper half of our faceoverly specific types of vasculature,meaning specific typesthat don't have capillaries between them,and as a consequence,heat and cold can move very quicklyfrom the palms of the hands,and the upper half of our face,and change our core body temperature.There's a name for theseThey're called AVAs orBasically veins and arterieswithout capillaries in between,which allows cooling ofmuch more quickly than is possibleby applying colder heatwhere capillaries interveneThese AVAs, arteriovenous anastomoses,can be leveraged to cool offyour core body temperature very quickly.The key thing is to getthe bottoms of your feet, andin contact with a cold surface or fluidthat is cold enough to cool the bloodand the core of your body,but not so cold thatjust below the palms of your hands,the bottoms of your feet, orSo, not placing ice packs necessarily,but maybe placing cool towelsthe palms of the hands, andand as they warm up, replacingThe exact temperature will dependon how hot you happen to be.I can't know that withoutknowing your particular circumstances.If you'd like to learn more abouthow to cool off your core very quickly,and some of the details andthat are being developed to do that,please see the episodeor the episode on cold.If you don't want to go to those episodes,here is a good procedureYou could grab, for instance,a package of frozen broccoliIf someone is really, really warm,make sure they take offget their feet on top of those.Ideally get some into their hands as well.Get some cool compresses andYou could, of course,also put a cool compresson the top of the head.That would be an especially good ideaif someone were hyperthermicbecause of the way thatunder conditions of hyperthermia.But the key point here is thatjust putting coldonto somebody's torso isas cooling those glabrous skin surfaces,the bottoms of the feet,and the upper half of their face.Similarly, or I supposeI should say, conversely,there are times when it is desirableto heat the core of the body.And once again,just simply throwing ais not going to be the most efficient way.If someone is hypothermic,it is not a problem toBut ideally what you do isor warm fluid to warm thetheir hands, and theOf course not so warm thatThis has actually been examined in studiesfrom the Heller Lab.Turns out that, for instance,to get people out of anesthesia,it is beneficial to warmAnd of course there is fever,which you should knowWhile fever is uncomfortable,and in fact often involves a mismatchbetween our perception of our shelland a perception of our core temperature.In other words,there are times when our bodywe have a fever, and yet we'reAnd that's because underthe immune systemthat impact, and in some ways,intentionally disrupt theand the way it normally functionsso that it can override peripheral signalsand simply try and heat the bodyand kill whatever pathogenSo for those of you that think about feveras always a bad thing, it's not.Now, of course we don't wantto go so high that tissues ofThis is one reason why, ifyou need to start gettingThere are times when youor go to a hospital,you really need to employ cooling methodsof the sort that I talked about beforeto prevent hyperthermia.Of course, safe rangesvary between infants and adults.So you can look those up online,depending on the person'swhat is not.But keep in mind that ifpills to reduce your fever,you are actually short circuitingthe protective mechanismAnd that's because most pathogens,bacteria and virus, don't surviveIn fact, in laboratories,if we want to preserve a virus for use,we put it into a freezer.If we want to kill a virus,So in many ways, feverof heat inoculationof various kinds.Now last, but certainly not least,I want to refer to theat the very beginning of this episode,involving what's called local hyperthermiain order to trigger a numberin fat tissue in order towhich is the metabolicallyMany of you, or at least some of you,should be familiar with the factthat deliberate cold exposurecan increase brown fat stores,these mitochondrial denseallow a person to feel more comfortablein cold temperatures, water, or otherwise,and increase core metabolism.I talked about this inbut very briefly, theis to get 11 minutes totalyet safe deliberate cold exposure,either through ice bath, cold shower,cold immersion up to the neck,or some other form of cold exposure.That triggers increases in brown fat.That's been beautifullyAnd that increase in brown fatin turn increases core metabolismand one's ability to feelThis was a study done in humans,and there's now ampleto support that thisthat I think most peopleLocal hyperthermia is aIt involves heating aas a way to convert theto beige fat, which in turnin thermogenesis andand believe it or not, in fat loss.Now, the study that I'm referring tois a very recent study that was published,again, in this terrificCell Press Journal.And again, one of the three top journals,Nature, Science, and CellTop because they're the most competitive,but also generally, not always,but generally the most stringentin terms of the review process.Papers that make it intogenerally are of very, very high quality.And certainly enough people see them thatif they're not of high quality,they get shot down pretty quicklyWhereas papers in other journalscan sometimes last a long timebefore they're ever replicated, et cetera.The title of this paperis "Local Hyperthermia Therapy"and Treats Obesity."This was a study that wasin the same study.What this study involved was heatingof a local patch of skinwhich is a 105.8 degrees Fahrenheit,but not damaging the skin.So the methods of heatingdid not involve placing somethingon the skin that would damage it.In fact, in the study on the mice,they used this kind ofin order to do it.And in humans, they used a thermocouplethat would allow them to heat the skin upjust locally in particularthat I'll talk about in a moment.They refer to this process asThe reason they did thisIt's long been known from clinical data.And in fact, from a bit of research datathat people thator unfortunately in some circumstances,significant portion of their bodyexperience overall decreases in body fatand increases in metabolismNow, of course, is notever want to induce burn inBut the observed increasesin response to skin surface burncouldn't be explained byrelated to the burn, for instance.And in fact, there are molecular pathwaysrelated to something called UCP1,which is uncoupling protein one.I talked about this alsobut don't worry if youor if you choose not to.UCP1 has the ability toin ways that increase corein particular, in beige and brown fat,which are these fat cells that existgenerally along ourin the upper part of our backand around our neck and clavicles.And they're responsible foror I should say the fuelthat can be burned up toSo, if you normally think about fatand you think about blubbery fat,you're thinking about white fat,which again is just a storage site.Beige fat and brown fat existmainly internally, around ourand those fat stores are responsiblefor generating heat in our body.So they're a very metabolicallySmall children have a lotin particular because veryA number of you probably didn't know that,but very young children can't shiver,so they need some way to generate heatin order to make sure that they stay aliveif they were ever to get cold.This is also probably thecan run around on a cold dayand they don't even seem to notice,whereas adults are freezing cold.As we get older, the amounttends to either reduce orIt's still debated which happens.But we know that whiteto this more metabolicallyby deliberate cold exposure,according to the protocoland now it seems, based on this new study,that local heating of skinand the effects of UCP1 onAnd in fact, that localthat is 105.8 degrees Fahrenheit,can actually induce the conversionof white fat to beige fat.Now that's pretty interesting,and I can already predict thein the kind of wellness and biohackingand longevity communities.I'm sure that pretty soonpeople putting heating padson different fat padstrying to reduce,or at least convert theAnd who knows, maybe that'll work.There have not been manyThis is the first, atof such studies looking atNonetheless, the data are mechanisticallyeven more interestingabout UCP1, and here's why.Local hyperthermia,using the protocol thatresulted in the increase of a promoter,which is essentially a mechanismby which certain genesThis is a DNA binding ofWe don't have to go tooor the nomenclature,but HSF stands for heat shock factor one.And HSF1 binding to a particular locationin the genome allowedwith a very long name.I'll just tell it to you for fun,but you can just let theIt's not important.HNRNPA2B1, shortened to A2B1,which frankly is not thatis still a name that should be meaninglessto most everybody, butA2B1 is directly involved inand regulates the genes that controlglucose and lipid metabolism.So here we have a situationconverted a metabolicallythe white fat cell, intoso to speak, beige fat cell, which in turnled to systemic, meaningthrough two mechanism.One mechanism is this increase in UCP1,which for those of you that want to know,UCP1 causes shifts in the waythat potential energy isthrough the mitochondria,basically more mitochondrial function,which means more ATP,which means cells are more active,AKA, increased metabolism,and increases in things likewhich are involved in lipidand glucose metabolism and regulation.So I want to be very clear,this study does notis possible with local heating of tissue.I just can see it now that once this papergets out into the press,oh, heating up a certain patch of skinis going to burn fat or convert fatto some other cell type at that location.Sorry, that's not the way it works.They did observe increasesat certain locations in the body.But those increases in beige fatoccurred where beigearound the spine, the upper neck,the clavicles, and so on.This is exciting because it providesyet another potential mechanismin addition to deliberate cold exposureto increase beige fat,meaning the metabolicallyIt also nicely provides a mechanism,or at least a potential mechanism,for the observation that burn,either small patch of skin being burned,or again, sadly largeleading to these veryincreases in body fat loss and metabolism.What, if anything, shouldWell, first of all, I wantabout putting anythingthe surface of your skin onto your skin.That would be a terrible idea.However, I do predict awhere people will start to explore the useof local skin heating as a meansto increase the conversionand in turn for beige fat storesto increase metabolism overall,and maybe even improve glucoseIf you'd like more detailwe will provide a link to itI should mention that the study,at least the portion of the studythat was focused on humans,involved roughly equalThe subjects followed theirincluding time and compositionrest and active hours,The local hyperthermia therapy was donein the following way.Here I'm paraphrasing fromSubjects were seatedThey were wearing a standard test robewith the head and neckand one meter away fromwhich could basicallyat their skin surface to make surethat it remained constantThe supraclavicular fat deposits,meaning the upper shoulderswere exposed to this thermal source,again, 41 degrees for 20 minutes.So it was 41 degrees for 20 minutes.And their core temperatureswere monitored before and afterthis local hyperthermic therapy.The subjects were exposed tothree days per week, separated by day,Monday, Wednesday, and Friday,so they had weekends off,after which their data were collected.And the study has a numberof other really interesting featuresthat are sure to lead toof both mechanism and new protocols,such as analysis of the genes and proteinsthat are activated downstreamof this local hyperthermia therapy.I find these data incredibly interesting,in part because of the waysthat local hyperthermia therapymimics deliberate cold exposure therapy.Same downstream mechanisms, UCP1,and some of the otherand all of that points to a somewhat new,but certainly an important concept.Many of you have probablywhich is the subjecting of one's self,or others, I suppose,to enough stress to induceSo hormesis is the reason whyif you get into cold water repeatedly,at first, it's veryand over time you get used to it.You never get completely used to it,but you get more used to it.Hormesis is also used toto cardiovascular exerciseof resistance trainingor the strengthening of musclesor the improvement into endurance exercise and so forth.Hormesis is a somewhatIf you haven't heardIn this paper they describewhich is, in essence,the fact that any number ofprovided they activate UCP1and some of these otherlike HSF1, can inducethat lead to increases in metabolism.So it shouldn't surprisecan both lead to increasesof white fat to beige fat.It shouldn't surprise us becauseLocal hyperthermia is stress.Burn certainly is stress.Sauna is a form of stress.Deliberate cold exposureExercise is a form of stress.And the adaptation to thoseAll of those protocols, anyis going to be effectivebecause it's going to convergeon an existing internalSo there's no uniqueEach protocol that I'vewhether or not it's fiveor four times in a dayor three times per weekis tickling or pushingon a given pathway andto a mild or to a severe degree.What I've tried to dois to illustrate the general mechanismsby which heat in particularcan activate certain biological pathwaysso that you can devise protocolsthat are going to be optimalSo just to briefly recap,if you want to get the greatestdo sauna or other deliberateprobably no more than onceand do it a lot that day.Just make sure that you breakIn the study I described30 minutes each.But that was just once a week.If you're interested inand the potential longevitywell then it's clear thatmaybe even seven times per weekis going to be more beneficialthan doing it just oneIt stands to reason thatin the general health effects of sauna,about an hour per weekmakes the most sense basedAnd again, that range ofis going to be your guide.And in terms of theit seems that getting ain that heat environment,provided it's safe, isto access those mental health effectsby way of increasing dynorphine,will then increase theto have its positive effects on moodafter you get out of the saunaor other deliberate heat exposure.And in terms of timing,morning or afternoon,or if you're not doing it after a workout,certainly in the later part of the dayis going to be most beneficialas it relates to sleep.But of course, there's a caveat there,which I will mention again,which is that for those of youthat have no trouble sleepingor you're just one ofwell then do it any time of day or night.But for most peopleis going to be more beneficialbecause of the post sauna cooling effectand the relationship betweenas a way to enter sleep.Thank you for joining meabout the science of heatIf you are learning from andplease subscribe to us on YouTube.That's a terrific zeroIn addition, pleaseon Spotify and or Apple,and on Apple you have the opportunityto leave us up to a five-star review.If you have comments orabout topics or guestson the Huberman Lab Podcast,please put those in theWe do read all the comments.Please also check outat the beginning of today's episode.That is the best way toAs also mentioned at thewe are now partnered withSo if you go to livemomentus.com/huberman,you'll find what we firmly believeto be the highest qualityin the specific dosages thatand recommendationsof the Huberman Lab Podcast.You will also find specific protocolsof how much to take and when,what time of day, whatAnd you will also find behavioral toolsthat can synergize with those supplements.Many of you will also be pleased to learnthat Momentous Supplements, of 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