583: Good stress is medicine | Sharon Bergquist, M.D.
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We've been told to avoid stress at all costs, but what if the right kind of stress is actually the key to longevity? Today's guest, Dr. Sharon Horish-Berkwist, is here to challenge our understanding of stress and reveal how we can harness it to improve our health, longevity, and resilience.

Sharon is a Yale and Harvard-trained physician, scientist, and she spent nearly three decades at the forefront of research helping people optimize their health through evidence-based strategies. Now she's sharing groundbreaking insights from her new book, The Stress Paradox, which explores why stress isn't always the enemy and how the right kind of stress can actually sharpen your mind, improve your health, and reduce your risk of chronic disease.

In today's show, we break down the differences between good stress and bad stress, the power of hormesis, and how everyday habits like exercise, intermittent fasting, and even plant-based compounds can help us build resilience at a cellular level. Sharon also dives into the science between mitochondrial health, the role of zone 2 and high-intensity interval training, and the simple yet powerful ways to incorporate minimum effective doses of movement into your day.

If you're looking for a fresh perspective on stress and longevity, this conversation is packed with science-backed strategies you can use today.

So how do you distinguish between good stress and bad stress? Yeah, and that's such a key question. So bad stress is the chronic continuous stress, and that's the stress that is the most common kind in our lives. And we've come to associate that stress with harm inappropriately because there are a lot of studies, including some of our own, that have shown the harms of this chronic continuous stress disorder.

Good stress are brief episodes that are acute stress and they're intermittent, so they're followed by recovery. And these stressors have a beneficial effect on us. And that comes from really several reasons at a physiologic and cellular level that we can talk about. So to build off of that, you have these five key stressors. And I immediately thought of exercise stress and high intensity interval training. So if we were to...

think about training in general, it feels like we could over-train in terms of doing too much all the time and we're a lot better off at the highest level having these short bursts of intensity followed by recovery and so on. Absolutely. So when you get the intense stressor, what you're doing is the greater the stimulus, the greater the adaptation, and that's what you want. So in the scenario of high-intensity interval training,

What's happening at a physiologic level, so that's at the level of our organs and our body systems, is you're getting a spike in cortisol. And that spike is what leads to the adaptations that help us muscle build. And it's very different from continuous release of cortisol. So cortisol is something that I think a lot of people associate with negative health effects, right?

But that's when it's at a low-grade continuous level. But when you are doing a HIIT training and the pattern of release is in this brief abrupt rise from the stress followed by the recovery, it's a very short-lived stress. And that type of exposure to cortisol is health-promoting.

So, and we've touched on this in other episodes we've done, but I think it's interesting. I want to spend some time on it. It feels like we're a lot better off rather than just doing, you know, call it zone two where, you know, maybe you're jogging, maybe you're rowing, or maybe you're doing a group fitness class where you're kind of in that 60 to 70% heart rate range and you're going and going and going and you're never really getting better.

to max heart rate, the 85% zone four or five plus, if you will. And then you've got the other where people are maybe training for an intense race and find themselves doing the, instead of spending, say, 45 minutes in a session and just zone two, they're spending 45 minutes in zone four and five. It feels like the correct way to train is to do your, call it zone two, but burst to zone four and five, then come back down and go up.

and make sure there's a variety in terms of intensity. Well, there is. And so there's value to all of these types of workouts because you have to really step back and ask, what is the goal you're trying to achieve? And depending on your goals, your workout routine is going to be a little different.

When it comes to good stress or hormesis, one of the biggest goals is building your cellular health because that is such a foundation of building your overall health. And in that scenario, the most crucial component of cellular health is our mitochondrial health.

So if we're structuring a workout routine to improve the health of our mitochondria, which our entire body, every energy system in our body, every cellular function repair relies on our mitochondria.

Then what you want to do is do a certain amount of zone 2, really roughly in an 80-20 pattern of about 80% the zone 2. And that helps us build the mitochondrial volume, build the number of mitochondria. So from biology class, we picture each cell having one mitochondria. But in reality, a cell can have hundreds, even thousands of mitochondria.

So what we're doing is we're increasing the mitochondrial mass. But if we only do a zone two without the peaks of intensity, about 40% of people don't improve cardiorespiratory fitness, which is one of the ways we can measure mitochondrial health.

So we need to get to a point of a greater stimulus. So we build the adaptation. So when we reach the higher zones, so with high intensity, really you can be in a zone three up to a zone five, depending on a person's fitness level and the type of interval workout that they do.

But what that intensity does is it activates different parts of our physiology that we would not activate with just continuous. So, for example, at a cellular level, we are turning on master regulators of mitochondrial biogenesis of forming new mitochondria via the PCG1-alpha.

master regulator, and we're also triggering mitophagy, which is a process of autophagy, of cellular renewal, where we're taking away the mitochondria that are damaged, destroyed, and we're replacing them with healthier, like renewing our mitochondria.

And you need that stronger stimulus to reach that peak level of mitochondrial function and mitochondrial health. So yes, you need some level of just building a good foundation in mitochondria, but that alone is not going to get you to an optimal state. And just to back up, if I were to guess, or maybe I'll just speak personally, why do I do exercise, specifically cardio?

I do it to improve my VO2 max because I want to increase my health span and I do it to feel good and I do it to hopefully slow the aging process, mitochondrial health. And I also want to do it in a way, I'm busy, I'm a parent, I work. I want to do it in a way that is efficient. I don't want to waste time. If you told me the minimum effective dose of

for this workout was three minutes a day. I would probably do three minutes a day, maybe a little longer to feel better, but time is something that is not necessarily abundant for me.

And so is it safe to say that this 80-20 rule, if someone is listening and says, okay, I want to feel good, and I think most people feel good after exercising, if I want to do cardio in a way that benefits my longevity in terms of increasing my VO2 max and increasing

potentially slow the aging process as it relates to mitochondrial health. This 80-20 rule, maybe I'm overthinking it and maybe just stick to this 80-20 rule. The 80-20 rule really comes from professional athletes. And the reality is

Probably for us, you know, a person that is not elite athlete but exercises regularly and is health conscious, it actually may be a little bit more than 20% because the amount of time we're spending at the high intensities is just going to be less in terms of hours.

So I like the way that you're really framing this as what is the minimal effective dose, because I think of all of these good stressors as medicine. In fact, they're the most powerful medicine that we have. And when we think about medicine, what we want to do is get kind of the

First, the lowest dose that is effective, and I'm going to come back to what that is. And what we're talking about here is the optimal dose. So it's kind of the sweet spot. And with hormesis or these good stressors, we call it the hormetic range.

So this 80-20 and perhaps closer to 70-30 for someone who's a casual exerciser is the optimal. But the minimum effective dose, and this is what's encouraging for all people who work full time, don't have a whole lot of extra time, kind of like myself, you know, with kids, etc. In the minimum effective dose, we use the acronym VILPA, V-I-L-P-A, so Vigorous Intermittent Lifestyle Physical Activity.

And in a study of over 25,000 people, it turns out that if you follow them for 6.9 years, if a person is doing one to two minutes of vigorous exercise at least three times a day, that cardiovascular mortality goes down 40%. All-cause mortality and mortality from cancer can go down 40%.

What that looks like in our daily lives is just running to catch a bus, running up a flight of stairs. So if we want to just get a minimum effective dose of this intensity, we can all do that throughout our day. And how do you define vigorous? Vigorous is getting yourself really zone three or higher.

So you are at a point where heart rate, I mean, you want to be 70, well, a little more than that. Ideally, say 80 to 95% is the ideal if you're doing it by heart rate.

If you're doing it through perceived exertion on a perceived exertion scale. So that's a scale from 1 to 10, where if moderate brisk walk is like a 5 to 6, you want to get to like a 7 to 10. Okay.

probably realistically seven to nine. Depends on how you're measuring it. And how long do you need to stay? And I'll just stick to heart rate because that's the easiest to measure. A lot of people have a wearable or an Apple Watch or a garment, what have you. How long do you need to maintain that? One to two minutes, three times a day. And that's the minimum effective dose. In some ways, I think that's easy. In other ways, I think that's difficult.

Because there's also what I find when I work out is there's a lag between often between perceived exhaustion and maximum heart rate. And so I'd say I'm like a fairly well-trained athlete in that I work out consistently and I push myself where

where oftentimes if I'm pushing myself rowing, for example, the perceived exhaustion starts to set in where my heart rate is probably a little...

call it in zone two or three. And then when I'm exhausted, it starts to like 10 seconds later, 15 seconds later, when I start to slow down, then it goes to zone four and five. And it's difficult to hold. Like it is. So that's like 40 minutes. If we're saying a couple minutes, three times a day, that's 40 plus minutes a week. Yeah. I mean, throughout the week,

So talk to me. So how do you do this? Because I know you're busy. So I do... What I like to do, which I find the simplest, is take whatever workout that I'm doing. Let's say if that day, let's just say it's walking or jogging. Do it in intervals. So if a person is a walker, one of your walks for the week should be done in intervals where you speed up for three minutes, you slow down for three minutes. You speed up for three minutes, you slow down. And if you look at...

a lot of clinical studies. There's a study done in Japan where they had middle to older age people walk in intervals versus at a continuous pace. And the group that walked in intervals had significantly higher cardiorespiratory fitness. So just doing that makes a difference. If you are someone who does exercise at a higher intensity, so I like to run, at least one or two of my runs I do in intervals where instead of

continuous pace running, I'm doing really a faster kind of sprint for several minutes, slowing down, catching my breath. Faster sprint, slowing down. If I'm on an elliptical, very similar. If I'm on a bike, very similar. So just think of it as

Just taking your favorite exercise and just doing it in intervals at least once, ideally twice a week. Very doable. So if this is the protocol and minimum effective dose for improving our cardiovascular fitness, improving VO2 max, I want to touch on mitochondrial health.

And so let's talk about mitochondrial health, the relationship between this type of exercise and essentially slowing the aging process. Yeah. So mitochondrial health is such a big part of cellular health. So if I kind of backed up and looked at all the hormetic stressors that we're talking about, one of the biggest goals is that we're trying to make our cells healthier.

And our cells are a micro version of our overall health. So that is why this is so important. In all of these various forms of hormetic stress, they've been introduced in different realms and almost feel like biohacking. But what I hope that we really change the mindset around is that these are really vital for general health. And the reason for that is they're making our cells healthy.

So mitochondrial health is probably the most important factor of that, but there are so many other cellular stress responses that are being activated by these stressors. We have actually seven cellular stress responses. They do things like improve our antioxidant levels, anti-inflammation. We activate sirtuins that help our energy and touch on the mitochondrial health.

We also have an autophagy response that helps with cellular cleanup. So we need to kind of think about it as a bigger basket of what we're accomplishing.

And the mitochondrial health has an outsized role because mitochondria determine our energy. We cannot do any of the repair, the growth, and the renewal that our cells need that we're actually activating by these cellular stress responses if our mitochondria are impaired.

So mitochondrial impairment is incredibly common today. Part of it is because of the aging process alone, and that reduces the efficiency of our mitochondria, it reduces the volume of our mitochondria.

But the environment that we're living in, as we all know, is not a healthy environment. So processed foods being sedentary, chronic stress, these are all factors that impair our mitochondria. When we deliberately choose good stressors, so we mentioned high-intensity interval training, but other ones can be eating plant chemicals, using heat and cold, intermittent fasting, even different types of cognitive and mental challenges.

What we are doing is we are improving our cellular health. So if

On the one hand, we have things that are damaging or harming ourselves. And our predicament really in our modern society is, well, how are we going to kind of work our way back to health? And so much of what we know to do is how to mitigate the harm, right? How do we try and eat less processed food? How do we try to avoid being sedentary? And that's where a lot of focuses of getting healthier come.

Through the good stressors, what we're doing is a little different. Instead of playing defense, we're playing offense. We're repairing the damage. We're taking an active, powerful control over our health.

Like the way we are stimulating our body triggers repair and regenerative processes. So when we're doing a good stress, we're taking mitochondria that's damaged from living in our modern world and we're replacing the mitochondria with healthier mitochondria and we're producing more of them.

So essentially, we are taking our cellular engines and kind of replacing them with better engines instead of clunkers, right? We're kind of upgrading the cellular engine.

So what our mitochondria are doing is they're converting food energy to chemical energy in the form of ATP. The more efficiently we can do that process, the more energy that our mitochondria produce, but that's more energy that we as humans have. That energy in our brain helps our cognitive processes. We think with greater clarity.

That energy powers everything from our digestive processes to how our stress responses even work. That's essentially what we're doing. We are taking an alternate approach to health where we're trying to mitigate the harm. And that is just such a critical piece because health.

In addition to our mitochondria, there's harm happening to our DNA. I mean, we get 10,000 injuries to our DNA every single day. That's seven a minute. And we have basal levels of these protective functions like DNA repair. If we didn't, we would be dead in days. But we are not activating our repair processes properly.

Enough. Like we have these inherent abilities, these defenses built in our body. But because we are living in a very comfortable world, this lack of good stress is not effectively mitigating the harm. So we're out of balance with our repair mechanisms and the lack of good stress is creating a risk factor.

for all the mental and physical illnesses that we're seeing today. Well, essentially, in my view, mitochondrial health is directly linked to how you age. And so mitochondrial damage equals faster aging in terms of how you look, how you feel, how susceptible you are to disease, to sickness, and so forth. And so that's the why aspect.

for me, when mitochondrial, when it impacts your cellular resilience, you're going to start to age. And just, and I want to walk through all the stressors, but just to kind of illustrate the point in my view, I think of two examples immediately come to mind. One is on one hand, you've got, you know, the stressed, someone who's stressed, you know,

financially putting food on the table, working 24/7, you know, maybe there's a health issue, they've got children, like that's extreme stress on one end, which is very real. On the other end, maybe you've got someone who's, you know, wealthy and doesn't really work, doesn't work and doesn't have purpose. And look, I don't want to discount financial stress because it is very real, but I would probably say that both extreme cases

are just as susceptible to accelerated aging. They are. So Jason, we've actually done that study. So one of the practices that I have is an executive health practice and we take care of CEOs of Fortune 500 companies. And we looked at stress and how it relates to biological age. So we looked at biological age by methylation patterns on the DNA to determine a person's

their true biological age versus their chronological age. And we looked at different levels of stress. And exactly what you just said, which is so eye-opening, you would think that, well, if the person doesn't have any stress, well, they're just going to age so much better. That was our hypothesis going into the study.

And interestingly enough, it was people who had kind of more of a moderate amount of stress, an amount that was comparable to normative amounts in America. If you took a cross-section and what the average stress level is by questionnaire-based information, the people who were at that level

kind of middle range had a slower biological age than the people who had no stress. This isn't a group that had low resilience. So you're absolutely right. Both extremes are harmful. And that is the most eye-opening part of this new science of good stress is

where we know that the chronic stress, like the person who has financial hardship, this chronic continuous stress is extremely harmful. But what's coming to light is that the other end of the spectrum, not enough stress, which is termed stress, is just as harmful as too much. And what we really want is this Goldilocks middle range that is the hormetic zone. So if you're listening and you're listening

you're wealthy and you have no issues and everyone's healthy, you've got to find some stress. You've got to find a good stress, right? So, and that's really it. So I think we need to think about stress management differently.

You know, we have this narrative stress is bad, we need to curb stress. But we also know that these good stressors build resilience to the chronic continuous stressors that we're trying to avoid. So the paradox is essentially that we need good stress to build resilience against harmful stress. So a new approach we need to take to stress management is differentiating good versus bad stress.

and then working to optimize the stress. So we spent a lot of time on exercise stress. I think everyone's got the memo to find their favorite exercise and find a way to do some interval training there. Let's talk about plant toxins. That's also a key stressor. It is a key stressor. So the plant toxins that I'm referring to that have this beneficial health enhancing effect are

are the phytochemicals that are in plants. And plants produce phytochemicals as a way of becoming more stress resistant in their environment. So plants are exposed to ultraviolet light, predators or pests that are trying to eat them. They're exposed to drought. These are plants that are in the wild, not the cultivated plants that we are getting in our food supply now. And they produce the phytochemicals to become stress resistant.

When we as humans consume the phytochemical, we get that stress-enhancing benefit. It activates our stress responses.

And those stress responses are the ones we're talking about that are improving our mitochondrial health, but they're also repairing DNA. We're repairing protein. We are recycling damaged components of our cells. So we are essentially taking the plant's mechanisms of stress response and it's conferring on us

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Investing involves risk. Offer is subject to terms and conditions. So what's on your plant toxin grocery list? What are your top five plans for those ready to pull out their Instacart or Amazon Prime and go shopping for some plant toxins? Well, there are, so the

the phytochemicals that have been the best studied are resveratrol, curcumin, ferulic acid, luteolin, genistein, EGCG. You don't have to really remember this. A simple way to think about it is that they are abundant in fruits and vegetables, and they're also found in legumes and some nuts and seeds and spices. So if you're

Filling up your shopping cart, getting the phytochemicals gives you stress resistance. So we talk a lot about, you know, what a healthy diet should look like. And certainly there are things that I think there's good agreement on, like we need protein. That is key. We need fiber. That is key. What often gets left out is the importance of phytochemicals and the diversity of these phytochemicals.

Because they are the components that are disease fighting. And if we aren't getting an adequate amount, there's more morbidity and mortality associated with that. So if you look at large epidemiologic studies like the Global Burden of Disease Study, which was done in 195 countries, carried out for 27 years. And what that study was looking at is mortality related to dietary patterns. And they found that

that the leading cause of death globally is diet. But the key takeaway was that more mortality and morbidity was caused by what we weren't getting enough of in our diet.

than what we were getting too much of, right? So we know that too much sugar isn't good for us. And this study also included too much meat as something that they thought was not necessarily helpful, although I know there's a lot of debate around that. But regardless, even if a person curbed sugar, curbed processed meat, it was mostly processed meat intake,

The number of lives saved would be orders of magnitude, like 30 orders of magnitude less than if a person added the plant foods with their vital phytochemicals. And I think that's a really important thing.

I think that it's important certainly to get the protein and the fiber, but only one out of 10 people in America are getting the recommended fruits and vegetables. And that is, so we're really missing out on so much health protection and disease protection. - So I still, I'm gonna push for a grocery list. You have to tell me what are your top five? Is it blackberries or is it carrots or you gotta give me something for my grocery list.

Well, I'll tell you the reason I'm not putting my personal, I'll give you my personal favorites just because I really want to encourage diversity than a superfood mentality, which is why I am kind of encouraging more abundance mentality.

But I love berries. I think berries have a very high amount of phytochemicals. And I would favor if people have access to getting wild, that's better than organic in terms of phytochemical load. And then organic has 10 to 50% more phytochemicals than conventional. But again,

Eating any amount is good, however you can get them. So berries, blueberries, I love strawberries, blackberries. So berries are high on the list. Green leafy vegetables, kale, arugula, different lettuces. Those, I think, are a really important part. I think that to get the health benefits, tea is really important. Coffee. Those are easy ways that I can consume them every day. Okay, you have me at coffee. I'm in. Okay.

And I love berries too. So another one on the list, hot, cold. So, and this one, I think minimum effective dose is very important because you could easily go overboard with either. Yes, you can. So hot and cold, again, both.

And the key here is that when you're exposed to an extreme of a temperature, and it's done in an abrupt way where you get that stress exposure from the temperature and then there's a period of recovery. What your body's trying to do is it's trying to get back to your core temperature. So as humans, we are all around 37 degrees Celsius, 98.7 degrees, roughly Fahrenheit.

And the reason our body tries to maintain that temperature is because our enzymes function optimally in that range. And when we are exposed to heat or cold, our core body temperature goes in either direction respectively. And our body wants to reestablish that temperature. In that process is when we release neurotransmitters and chemicals that improve our health.

So they're, again, working like a stressor. And that's the common thread with all of these health enhancing practices that we're doing. And what's happening, we can take each one separately. So if we took a cold, we can look at what's happening at a physiologic level and then again at a cellular level. At a physiologic level, when we're exposed to cold, we activate brown fat, iron,

And brown fat is a special type of fat that is around our collarbone, our organs like our heart and our lungs. And it functions very differently than the white fat, which is the kind that's around our belly.

The brown fat is like our internal space heater, and it's very metabolically active. It's trying to generate heat to keep us warm. And the key here is that in order to produce that heat, it's utilizing fats and sugars and it's raising our metabolic rate. So one of our goals really with all of these health practices comes down to what we're talking about, our cardiometabolic health.

So by utilizing the fats and the sugars, it's improving our cardiometabolic health. But a key part of

restoring our body temperatures, temperature is also shivering, right? So we have shivering thermogenesis to restore heat and non-shivering. The brown fat is the non-shivering thermogenesis and the muscles contracting in a way that generate heat instead of propelling us, you know, in a direction, which is what we use muscles for when we're exercising. And

The contractions are also raising our metabolism. And because we have really a lot more muscle mass than we do brown fat, most of the increase in metabolism and caloric burning is coming from shivering and from muscle contraction. So it is a method, again, of improving our cardiometabolic health, which is so critical. And that's at the physiologic level. At a cellular level, as you...

Our depleting energy, that is the stimulus for us to make more mitochondria. So it activates cellular key master regulators that help us and stimulate the growth of new mitochondria. So at a cellular level, it's also helping us and it's activating our other stress responses that occur at a cellular level, improving our antioxidant defenses, reducing inflammation, improving DNA damage, etc.

So that's what we're getting out of thermal exposure. And that's why it's really health benefiting. I know there's a lot of attention on it recently, but it does have physiologic benefits. And then the other part is also what it's doing for our brain health. We're getting a huge spike in norepinephrine up to like 530% and a spike in our dopamine up to 250%.

And that improves our alertness, our motivation. And, you know, so but you ask about what is that minimum effective dose? And this is where it depends on which modality you use. So if you are using a cold plunge and you are doing complete water immersion, most studies are using 50 to 60 degrees in that range.

And you want to do really about three to five minutes. You can start with 30 seconds. It's not so critical to hit a particular temperature or duration. What really matters to get the benefits, this hormetic zone, is it's got to feel uncomfortable for you. So you want to go past your comfort level, but to the point where you still feel safe and do that for a short duration.

And when you get to a point where you no longer feel like this is safe and your body is just kind of telling you that this is now potentially getting to the point where you can sense the discomfort is at a different range, that's your threshold.

So with all these protocols, there's so much individuality that it's more thinking of it in terms of here's an overarching principle. And that's what I encourage for people when I design a protocol. Here's a framework and customize it, right? People are going to come at it with different levels of cold tolerance. So what's right for you and what's right for me are going to be different, right?

But what's really the commonality is you've got to get uncomfortable in the service of reaching a higher potential and adapting your body to a greater level of stress resistance. It's interesting in that I think the science is still developing in terms of cold therapy. I've read that

11 minutes over the course of a week is maybe the minimum effective dose ideally spread across multiple sessions and that once you go above that unclear if there are increased benefits or maybe perhaps diminishing returns.

Also read, as it relates to women, they probably want to be a higher temp, so like north of 49 degrees. They shouldn't go lower. Men may be a little lower than that. And then for me personally, what I find to be interesting, there really isn't much science here. Anecdotally, I know some people have had success here, and I think maybe there's one small study for men.

there's interest around increasing one's testosterone naturally via the cold plunge. That's a whole different protocol in terms of frequency, duration, temperature. I've done some experimentation there. But I agree with your point, be uncomfortable, but you also don't want to kill yourself doing this.

Because you could you can really inflict damage if you jump in and try to do, you know, 10 minutes on day one at 40 degrees. Correct. Because you can take any good stress and make it a bad stress. Right. Because your body simply doesn't work in a way where you need it to be a continuous high level. Right. It's like overtraining. Right.

So exactly, the goal is not to get yourself to be in freezing temperature for 30 minutes. Like that's not the goal. You're actually building your chronic stress. So if you think about what every stress is doing, stress is essentially something that throws your body out of balance and that balance we call homeostasis.

And your body's striving to get back to balance. It's striving to reestablish homeostasis. But some of the energy that your body needs goes towards reestablishing it. The amount that your body uses for growth adaptation to build things, like you said, a higher testosterone level, a higher growth hormone, depending on the protocol that you're using, is

You can use about 25, you can get about 25% growth or benefit because the body needs to reestablish homeostasis. So when you go to a higher amount of stress, you're not getting more health benefit. So hormesis, the science of good stress, has been studied with polycystic.

plants, different organisms. It's been studied with thousands of toxins. And there seems to be an upper limit to the growth and resilience that you build of 20% to 25% from any single exposure. But the key here is that with any health habit, you don't just want a one-time exposure. You want to do it on a repeated basis, right? That's how you build long-term adaptations. And if you do this stress, recover, repeat, stress, recover, repeat,

You can increase the human potential 60 to 90% over time, right? You can almost double your human potential, right?

But you want to do this again through mild to moderate stress because there's a ceiling benefit of any particular stress. Yes. And two things I just want to call out just to remind people. You mentioned let your body cool off. Always let your body cool off. Don't go... I made this mistake when I first started a couple of years ago. I went straight to the shower mistake. Let your body cool off naturally. Don't go cold hot. Always finish on cold.

So one, you could really do some damage. Two, if you're doing resistance training, do cold before you train. Don't do it after because you could be inhibiting your body's ability to grow muscle. And something to zoom out what you said, I think there's this larger concept, which I think is interesting. There used to be a perception culturally, I'm getting older. I'm not going to do that anymore. I got a case of the 40s. I got a case of the 50s. I'm going to slow down.

And this notion that we were maybe embracing comfort as we age. And I did this too, that it feels like we've been completely wrong here.

And we may have done ourselves a disservice in terms of our ability to increase our health span by embracing this mentality of I need to like slow down a bit when reality is the answer is no. We need to continue to push ourselves. Why we do need stress. This idea of, you know, I'm going to retire and play golf and take it easy and have no stress. Like, no, that is not what you want to do. And that's

there seems to be culturally this shift driven by, you know, biohackers or longevity bros for better or for worse, who've rejected this notion of, no, I'm not going to age. I'm going to live forever. Maybe that's a little ridiculous and I'm going to push myself. And I think that's really interesting. And that alone is,

this mindset shift, which I'll touch on mental and emotional challenges of like, no, like you shouldn't just rush to retire. No, you shouldn't be too comfortable on vacation. Maybe just a little comfortable vacation. Like you need to push yourself. That is a big unlock. Hugely important because it's touching on how our body works. Our

Our body works through bioplasticity, and that's really the biological way of saying use it or lose it. And when we aren't pushing ourselves, we're essentially becoming more vulnerable to mental and physical illness. And that's exactly right. Our life of

comfort is really a product of modernity, right? Our ancestors were exposed to all of the physiologic stressors that we're talking about. It was a way of life, old and young, women and men, right?

And as we have introduced a lot of technology and modernity industrialization, we've removed these comforts, right? We're in air-conditioned rooms that are heated. We have food available 24-7. We really don't have the need to be sprinting and doing vigorous activity. But that is the stimulus that our bodies have grown to adapt to, to get us to a state of optimal health, right?

When we do it in our brain through cognitive processes, we call it neuroplasticity. But essentially, you've got to push your limits to grow your limits, right? The more you get out of your comfort zone, the more you expand your comfort zone. And the less you do, the more you contract that zone. And that is what we are missing about, you know, part of the big contributor really to so much of the rise in chronic disease is

And so I think you're absolutely right. We need to change that mentality. And that's really why I think we need this new approach to stress management. Agreed. And I want to come back to, I know I zoomed out here. We were on the hot cold and we got to cold, we didn't get to hot. So let's come back to hot.

And so how do you think about sauna, heat exposure, minimum effective dose, frequency, all the above? Yeah, so with heat, so again, what your body tries to do is if your core body temperature goes up, your body needs to dissipate that heat. So it's going to get more blood pumping to your extremities so that you can sweat off that extra heat.

And it does that by raising your heart rate. It raises your blood pressure and it mimics physical activity. So moderate to vigorous exercise.

And it produces a special type of stress on your blood vessels called shear stress from that blood motion. And the shear stress tells our endothelium to produce more nitric oxide, which is a very magical molecule for protecting our cardiometabolic health. So nitric oxide...

is a molecule that dilates our blood vessels. It also has protection against clumping of platelets or antiplatelet activity. It helps prevent cholesterol plaques from forming.

And this is all about how do we get upstream to prevent chronic disease long before it ever manifests. And our endothelial health is really critical. If you have endothelial dysfunction, just like if you have mitochondrial dysfunction, these are changes that occur at a cellular level that are predisposing us to plaque formation, to stiffening of our arteries. So essentially the heat is

is making our body produce natural molecules like nitric oxide that are protecting us against cardiometabolic disease. So that, again, is at a physiologic level. At a cellular level, once again, the stress of the heat is activating our cellular stress responses. With heat, one of the biggest things it does is there's a spike in heat shock proteins, raises them by about 50%.

And heat shock proteins help repair our proteins. So they take unhealthy, poorly formed proteins and they are molecular chaperones. They essentially escort those damaged proteins out of our body. And that's so critical because you're mentioning aging, and this is true of all chronic disease. At the crux,

are damaged to our DNA. Like you mentioned, mitochondrial dysfunction, but essentially there are nine hallmarks of aging with mitochondrial dysfunction being one of them. But the nine hallmarks of aging are the processes that we know that are contributing to the aging process.

And if we can slow these processes, we are slowing aging. And these same processes, because they lead to chronic disease, we are reducing our risk of chronic disease. So in addition to mitochondrial dysfunction, there's genomic instability, attrition in our telomeres. And here's where the heat shock proteins come. Loss of balance in proteins or loss of proteostasis is a contributor to aging and

and the clumping of proteins is also a precursor to dementia, like Alzheimer's dementia. So by exposing ourselves to heat at a cellular level, we are removing the damaged proteins, improving the health of proteins, and that is a mechanism by which we're protecting ourselves from chronic diseases like dementia, and we're protecting ourselves from or slowing the aging process, essentially.

And minimum effective dose. So here, again, what you'd referenced with sweet spot of the 11 minutes of cold, that same study with Susanna Soberg also included 57 minutes of heat. So doing 11 minutes of cold, 57 minutes of heat seems to be the minimum effective dose. And generally what you want to do is spread that over several sessions over the week with each session having some contrast therapy of heat and cold.

and kind of getting that sweet spot amount. But if you want to get an optimal amount for protection, that's going to be more than that minimum effective dose.

So we have studies from Finland, a big, large Finnish study that I think often gets quoted as a QPO ischemic heart disease study, where they followed over 2,000 men for two decades. And they found that men who use sauna four to seven times a week compared to men that used it once a week, which was the control group, of course, in Finland. So people who did that had

a 50% lower mortality from cardiovascular disease, again, which is not surprising because sauna mimics exercise. They also had 65% lower risk of dementia, Alzheimer's dementia. Again, what's good for the heart is good for the brain, but it also activates heat shock proteins and creates a cellular benefit for brain health. So you would do more, so essentially four to seven minutes of sessions that were about 20 minutes or more, essentially. So more is...

yes, you can do more to optimize. So 20 minutes or 57 a week at a minimum effective dose or 20 minutes a day if you really want to optimize. Do we know the temperature? So these studies have largely been done with saunas, the traditional saunas. What we know is this rule of 200, so you can have different levels of humidity and heat, but the rule of 200 is you want the heat and humidity to add to be 200.

And so of course, Finland has like a monopoly on the sauna studies. I feel like the Scandinavia saunas are everywhere. It's part of their culture. But I have to call out, it's a study of men. And, you know, women are not small men.

How do women and men differ as it relates to all the key stressors we've talked about? That's a great question. And most of these studies are primarily in men, but there are longitudinal studies in Finland that have included women. So we do know that there are similar benefits in women. Just some of the biggest ones are the men only. So some of the differences...

really relate to our nutrient sensitivity. So women are more nutrient sensitive. If we fast, we will kind of have a lower threshold of actually feeling the effects of it physiologically, hormonally. And women have slightly more metabolic flexibility.

Now, we have very few studies on women with these stressors in general, so I don't want to overemphasize what we know about this. But I'll say that a lot of studies are also done in women who are in a healthy state.

And we have to think that average America now, unfortunately, is not in a healthy state. A lot of people have some level of metabolic disease. You know, it's estimated that 93% of America has some metabolic disease. So some of the differences, so for example, in metabolic flexibility, are probably going to be overshadowed by poor metabolic health.

So, you know, I think what we're trying to do then is really there's optimization that we're trying to do. I mean, at the end of the day, whether you're a man or a woman, we use the same energy systems, right? We're still using glycolytic pathway and the oxidative phosphorylation pathway to generate energy. We don't have entirely different metabolisms, but there are just differences in optimization of what we need to do.

And that's what we're targeting. But again, this isn't a healthy population. And all people, men or women, are going to benefit from doing what we just talked about in Zoom, to exercise and improving mitochondrial health, even though women come at it with slightly more metabolic flexibility in a healthy state. Well, I'll touch on circadian fasting. You talk about that in the book. And that's one where it feels like

women who are probably in their 30s, 40s, 50s, and so on,

probably shouldn't be fasting for extended periods of time frequently. And if they are doing heavy training in the morning, they should probably eat. Yes. So I think it depends on how you define fasting. And I agree with you because when you think of fasting, you have to think of gender, age, a person's baseline health,

And the goal that a person wishes to accomplish from doing the fasting, right? Because it's going to be... Assume for the purposes of this interview that someone is fairly active and healthy. Right. So then I would say the circadian fast because circadian fasting to me is essentially normal eating, right?

You want to. I mean, that's really what I'm advocating. You're not eating in the middle of the night. You're not eating late at night. There's a 13-hour window. 100% it. So that's how our bodies are physiologically designed. So the average American is now eating over a 15-hour day. And our body needs time to grow and store food and energy, and it also needs time to break down energy and to repair energy.

And if we don't go more than 12 hours without eating, we are impairing our ability to repair and regenerate our body and our cells. So we are out of balance. And that is what's contributing to so much of the cardiometabolic disease. We're spending too much time in buildup energy storage phase and not enough time in breakdown phase where we're repairing our body.

It's very doable to what I, you know, 13 hours, you're talking 6pm dinner, 7am next meal, and like 12 hours is probably fine too. I think to the other thing, you know, as women and men get older, they're

The focus also becomes maintaining lean muscle mass, which we're losing at 1% each year after age 40. And so getting enough protein and is also, so if you start to stretch that window of, let's say you're doing a 16, eight fast, I've got eight hours to eat and I'm 125 pounds. Well, how am I going to get that protein? Like I'm going to wither away. Yeah.

It's not possible. A hundred percent. I mean, I have played with this. I'll start by saying 16-8 is based on rodent studies. We don't know what the optimal amount is for humans. But we do know that if you go more than 12 hours, you start to get the metabolic benefits of fasting, ideally closer to 10 hours. But you've got to balance that out with exactly what you just said. You've got to get protein. If you are fasting for a prolonged amount of time without the protein, you lose muscle mass.

And again, I am not a woman. But, you know, anecdotally, I made the mistake. I started to, this was like five or six years ago, started, you know, fast 16, 8, 18, 6, and I'm 50 now. This is like my mid 40s. I started to lose muscle. I started to lose muscle mass.

Same. And I was like, whoa, what? Like my legs, what's going on here? Same. I do closer to a 10-hour interval for the very same reason. It's very hard to get the protein that you need in a shorter timeframe. And some people can and more power to them. But you have to individualize all of these stressors to what works for you, depending on what your goals are. We didn't talk about mental and emotional challenges, but people can pick up the book.

I'm curious, what's had the biggest impact for you personally? Of the stressors? All of this, yeah. For me, it is giving back control over my health, right? Because we feel that there's so much that is not in our control, right? We know the environment has pollutants, toxins, microplastics, and...

And it's become very fear-based of all the things we have to avoid. And the mindset around good stress is a growth mindset where I embrace the challenge because I know that the growth is inescapable from going through these hard things. Our bodies need these hard things. And I welcome the challenge. And that mindset difference is the mindset of growth. And for me, that's where the power is. So...

You're a parent of three girls. Your girls are older than mine. I'm a parent of two girls. And I think about this a lot. I think as a parent, you do want to protect your kids. You want them to have a great life. But you do want them to have a growth mindset. You do want them to be exposed to stress. I don't think you necessarily want to send them out in the woods and say, go survive. Go...

figure out how to live. But on the other hand, you don't want to shield them from everything. How do you think about that as a parent? How do I instill this growth mindset? How do I expose them to just enough stress to develop the resilience that is necessary for success in life, a happier, healthier, longer life?

I think about this so much as a parent because our tendency is to go in there and fix it and make it better and to help them. But the first part starts with realizing that you are not actually helping them when you do that. And microstress is what they need in their life. So microstress is...

you know, not childhood adversity. No one's going to advocate for that. But micro-stress is if they have a homework assignment tomorrow and they didn't do the project and it's late at night and they are struggling a little bit, that's their struggle. If they have a sports competition, let them endure that stress. Like it is very healthy for them. Essentially,

Let them struggle just a little because what you are doing is allowing their brains to upgrade. When you let your child or even us as adults go through stress, we are releasing growth factors, brain-derived neurotrophic factor. We're releasing neurosteroids that are creating stress.

pathways in our brain that help us remember how we handle the stress. If you want your child to be able to handle future stressors better, you have got to help them upgrade their biology, to reconfigure their brain, essentially to go to a 5G network. If you are doing everything for your child, your child's going to have a

a DSL network. I love the timing of this. Literally last night, our older one had a bit of a meltdown around homework. Maybe stretch the truth about how much was done and that it was late at night and needed help. And both my wife, Colleen, and I were just like, figure it out. We're not helping you. Go to your room. There was some screaming involved and a meltdown. And then we said, wake up early in the morning and do it. We're not doing it.

It was a little, oh, it was a 90 minute, like it was, it was an ordeal. When your child is older, the amount of resilience that they will have is greater. And we, I mean, this is really the concept of stress inoculation, right? So you can think of stress like a vaccine, right?

And these micro doses are building your immunity to bigger stress. And it's been done. Really, a lot of studies we have around this are animal studies. But Karen Parker out at Stanford had done a study on baby squirrel monkeys where she separated the monkeys one hour a week from their parents thinking, OK, is that going to be traumatic? How are they going to do?

And interestingly, as those little baby monkeys got to be older, they were more curious. They started exploring with different toys. When they became adult monkeys, they were better at decision-making. The areas in their brain that control decision-making and fear were actually more resilient. And it's profound what it does. I mean, we can create new brain cells through this stress because of mindfulness.

the nerve growth factors that we release in the stress response, right? So what we have to remember is that the stressor of these acute brief stressors, they're brief. The effect they have happens hours to days later and arguably throughout a lifetime through epigenetic changes. So you're essentially reprogramming your body to this hugely resilient state of

And that's what you want to build your defense against whatever life brings you. Well, I think you just made every parent happy who's ever put their foot down during their child's meltdown for homework or whatever they're dealing with. I think I'm going to make our eight-year-old listen to this clip. Yeah.

We covered a lot, Sharon. Is there anything we didn't cover that you want to touch on before we wrap? I'm going to just say that I believe that every person has a limitless potential to live a better life. And the path to getting there is going to involve discomfort.

But just know that when you are using discomfort in the service of becoming stronger, healthier, and happier, that the biochemical reaction you're triggering by that type of stress is health-promoting.

And that's an inescapable part of growth. And we don't have to stress about stress. We just have to differentiate the types that are draining our energy, the types that are helping us grow and regenerate and shift the type of stressors that we have in our life. Amen. Sharon, thank you so much. Everyone go pick up the book. It's a good one. The Stress Paradox. Thank you so much.