Dr Rupy: Today I'm going to talk you through five ancient challenges that could activate your innate stress pathways that could improve your brain, heart and metabolism because it seems, at least in theory, that getting back to nature is the best medicine for the prevention of disease.
Dr Rupy: Hi, I'm Dr Rupy, I'm a medical doctor and nutritionist. And when I suffered a heart condition years ago, I was able to reverse it with diet and lifestyle. This opened up my eyes to the world of food as medicine to improve our health. On this podcast, I discuss ways in which you can use nutrition and lifestyle to improve your own wellbeing every day. I speak with expert guests and we lean into the science, but whilst making it as practical and as easy as possible so you can take steps to change your life today. Welcome to the Doctor's Kitchen podcast.
Dr Rupy: Could modern life be a little bit too comfortable for our ancient bodies? This week, I'm going to be exploring the idea that 21st century lifestyles might be mismatched with what our biology evolved for and how reintroducing a few ancient challenges could help you feel sharper, calmer and more resilient. Now, without going full caveman, there are a few mild and natural stresses that may have benefits to our bodies. And considering how comfortable our lives are today, would require us to purposely reintroduce. So I'm going to dive into while mild hunger and thirst, a bit controversial I know, might be of benefit. So not only craving needs to snack, your stress hormones might actually thank you. How plant toxins, quote unquote, are misunderstood heroes. So everything from broccoli to turmeric, these phytochemicals that are contained within these plants trigger powerful cell protection pathways. And I also talk about whether saunas and cold plunges are actually worth the hype and how short exposures to heat or cold separately, very important they're separately, might boost metabolism, improve circulation and even support our brain health as well.
Dr Rupy: Today's episode was heavily influenced by the conversation I had with Dr Leo Pruimboom about the science of intermittent living. The benefit of these challenges isn't in the challenge itself. I want to repeat that. The benefit of the challenges isn't being all hot. It isn't about being super, super cold. It's in the recovery. The fasting, movement, temperature, stresses, what these do is they mirror the environments we evolved in and it's our body's adaptation process, that's where the magic lies. So to enjoy the benefits of these, I don't think it actually requires a complete lifestyle overhaul. I see these as gentle nudges to remind your body what it was built for. And the key is dose, not too much and not too little. And I also want to just make the point that this isn't a one size fits all formula. It's a more of a curious invitation to explore how mild, short term stresses can unlock long term health. These aren't replacements for healthy habits, just small extras that might make a big difference. And this area of research is still very much evolving. Not all ancient humans lived in the same way and there wasn't one perfect lifestyle. And while the theory behind intermittent living is fascinating, which is what these ancient stresses and ancient challenges are all based on, it's not necessarily a prescription. I think of it as adding a few evolutionary ingredients back into your modern life and you can chop and choose which ones you prefer. Some people like fasting, some people like sauna, some people like cold plunging. You don't necessarily need to do them all. You can do one or none of them. It's completely up to you. My personal favourite are the plant toxins and we get into that a little bit later as well. So I really hope you enjoy this podcast I'm going to be doing all about the five ancient practices to help you feel better and function better as well.
Dr Rupy: Okay, let me set the scene. So for nearly two million years, early humans lived in small, mobile groups that had to provide for all of their own needs: food, water, shelter, protection, without any outside help. This self-sufficient lifestyle wasn't just a cultural thing, it's not something that we opt into like we have to now. It actually reprogrammed how our bodies responded to stress. And the challenges of this ancient living shaped our biology and hard wiring that we still have today.
Dr Rupy: This sort of constant DIY survival mode helped sculpt both our resilience and our physiological stress systems, like the hypothalamic pituitary axis, for example, abbreviated to HPA, our sympathetic nervous system, the fight or flight, if you like, the neurohormonal regulation. And these systems evolved not just to protect us, but also to help us perform better under pressure because we used to live in a very, very high pressure environment. Whether that meant solving a problem, fighting, fleeing, or just adapting to scarcity of needs like food. You have to sort of think of your body like a smart engine designed for an off-road terrain. So if you only ever keep it in a warm, toasty garage, it like rusts. It's made to move, adapt and repair, not sit in comfort all day. I hope you're seeing the analogy now with how this is completely antithetical to modern living.
Dr Rupy: Now, I don't think we all have to live an extreme lifestyle. I want you to think of these five challenges as perhaps an extra thing on top of your diet and your exercise to do if you choose to. It's almost like the cherry on top, almost like a supplement. And I think there's a lot of nuance within all these things that I want to ensure that I'm being reflective of and appreciative of. Male and female differences, things like cycles, menopause, younger generation versus older generation, genetic, the combination of all these different challenges, what kind of diet you're on, all these other stresses, it's very hard to study and ascertain which is the best for you. So with those caveats in mind, let's dive into some of these five ancient challenges for your health. The first thing is fasted exercise. Skipping breakfast and moving your body before you eat could be one of the best ways to protect your brain and your metabolism. There is one ancient challenge that I think is undeniable. We will have undoubtedly had a lack of food. For millions of years, our ancestors didn't wake up with food already on the table or in the fridge or in our kitchen. They had to move, hunt, forage, climb, often in a fasted state before they could eat. And this sort of feast famine rhythm was part of everyday life. Fasting wasn't a diet trend like it is now, it was just a natural order of survival. You have your effort first, so you've got to go out and hunt or gather or whatever it is, and then you have your reward.
Dr Rupy: So this fast then eat pattern could do something amazing to the body and brain, activating cellular responses, these cellular stress responses that make your body more resilient. So what happens when you're in this fasted state is that you get glycogen depletion of your liver. So glycogen is a storage molecule of sugar and we keep this in our liver and muscles. And by intermittently fasting, i.e. where you don't eat for a long period of time, so typically more than 12 hours, it obliges the brain and other organs to flip and use the byproduct of fatty acids called ketones instead of sugars. So you have this metabolic switch that benefits the brain and the heart and the muscles, which improves their functionality and it gets them used to switching between different fuel sources, between using fats as a fuel and then using carbohydrates as a fuel. So essentially, this whole practice of intermittent fasting and this fast then feast could promote something called metabolic flexibility, which is exactly what I've just described. This ability to switch between burning sugar or carbohydrates and fat efficiently and going between the two of them as simply as flicking a switch. And this is really key for preventing metabolic disorders like type two diabetes and obesity.
Dr Rupy: And this combination of fasting and activity also stimulates something called brain derived neurotrophic factor, something that we've talked about quite enough, quite a lot on the podcast, also abbreviated to something called BDNF. It's a growth factor that promotes neurons and supports learning and rewiring and memory. It's something that we all want to be doing. And one of the key things of, I mean, even exercise alone will promote BDNF. There are certain foods that will promote BDNF, but it seems that this combination of fasting and activity stimulates this even further as well. There's also the idea that fasting or intermittent fasting can enhance mitochondrial production. So these are the powerhouses of our cells. And more pragmatically, it gives your gut a rest, which means the microbes that are in the large intestine, slaving away day in, day out without a pay rise or anything, we give them a bit of a break. They can actually have a bit of a relaxation period and your gut tight junctions are nice and tight as well. Again, more pragmatically, if we do intermittent fasting in the real world, what it does is it reduces the energy consumption that we tend to be over consuming. Because we have food available to us all the time, we eat out of boredom, we eat out of comfort, we don't necessarily eat out of necessity. And so it essentially gives us a calorie restriction with a gentle guide, which is why I'm a big fan of at least having a 12 hour fast every single day.
Dr Rupy: On the subject of fasting and calorie restriction, both, and I want to highlight this because I think the fasting types that you find on YouTube or people who are promoting fasting lifestyles don't really recognise that the same can be true of calorie restriction. Simple calorie restriction of 100 calories less than your burning every single day, then your needs every single day, or 500 calories, it doesn't really matter, but both of these practices influence a key aging regulator in the body called mTOR, also called, also known as the mechanistic target of rapamycin. It's a protein that controls growth, metabolism and repair. And while mTOR boosts growth in youth, this constant activation of mTOR later in life can accelerate aging and other things as well, things like cancer. So you want a bit of a rhythmic tuning and turning mTOR on and turning mTOR off. And while mTOR boosts growth in youth, constant activation later in life can actually potentially accelerate aging. So what we want to do is have this almost rhythmic turning on of mTOR and turning off of mTOR. And we can do that through fasting and it potentially can slow aging. We know this from animal models, we know that people who are on a persistent or animals that are on a persistent low calorie diet, it does slow aging. This is one of the potential mechanisms behind that. There may be an issue with muscle preservation. So if you are constantly in a calorie restricted state and you're not consuming enough protein, it could actually be detrimental for muscles. So there are some issues with doing this in the real world that we'll get to in a second. But the overwhelming idea and the overwhelming opinion is that this practice could support long term health.
Dr Rupy: Now there lies a problem. Whilst we know that intermittent fasting, calorie restriction and other things and the fasting and then activity and then feasting afterwards, whilst we know that these have benefits, the dose and who this is most effective for is really, really varied. The effective dose is likely to vary from person to person. And you know, this could be based on sex, it could be based on genetics, it could be based on pre-morbid state. So is someone who is already got a metabolic disorder like obesity or type two diabetes, what type of fasting is going to be most appropriate for them? The common approaches for fasting include time restricted eating. So this is eating within a daily window of, let's say, eight to 10 hours and you allow an equivalent, well, a larger amount of time where you're not eating. So that could be 14 to 16 hours of fasting. And then the other mechanisms, the other practices are having a longer fast, so 24 hours, 48 hours fasting where you just drink water and you do that once a month and some people do it once a week. I think that's on the extreme side. Personally, the way I do it, and this is after years of figuring out how I feel, how my gut feels, do I feel energized for the rest of the day? I have a fast overnight of at least 12 hours, so I'll finish my eating at around seven or 8 p.m. latest. I will train first thing in the morning, so I usually go to the gym at 7:30 or probably earlier than that, around 6:30. I'll do whatever exercise I'm doing that day, could be HIIT, it could be strength, it could be zone two training, and then I'll break my fast around 9 or 10 a.m. So I'm usually fasting for a minimum of 12 hours every single day. And that works for me, keeps me metabolically healthy, all my numbers are great, my cholesterol is low, etc, etc. But this might not be suitable for everyone. I mean, especially if you are pregnant, for example, if you have certain medical conditions or those with a history of eating disorders. But we know that almost like obligatory intermittent fasting has been a part of human evolution during thousands of generations and humans should be well adapted to it. So I would choose a fasting practice for you that's most appropriate. And if you want to, try fasted exercise because there is some evolutionary evidence that this might be beneficial for our health.
Dr Rupy: The second ancient challenge is really, really controversial, so I'm going to try and unpack it as much as possible. What if mild thirst, so having not as much water, instead of constantly sipping, which I'll be honest, I pretty much do most days, what if this is actually nature's way of calming your stress and balancing your body? Sounds pretty out there, right? Well, thirst might actually be healthier than you think. In our modern world, we're often told, and I'll be honest, I've said this to many people, to stay hydrated throughout the day, carry bottles of water everywhere you go, sip water even if you don't feel thirsty, make sure you're drinking at least eight glasses of water a single day, every all that, you know, the stuff that we know, and I'm actually going to take a sip because I'm getting a little bit of dry mouth. But our ancestors may have had a healthier relationship with thirst and one that actually helped them manage stress and boosted their wellbeing. So, again, this is largely theoretical, but there is some science behind this as well. So for most of human evolution, we just look at it through an evolutionary lens, we didn't carry water with us. We didn't have bottles, we didn't have taps at arm's reach. And just like wild animals, humans drank intermittently when water was available and when thirst kicked in. Early humans, very similar to animals, had to move between water holes, sometimes going hours or even days with little water. Newborn babies, I've just had a baby eight months ago, well, I didn't have it, my wife had a baby eight months ago, they actually still show this ancient pattern according to some evolutionary scientists. They cry for fluids more often than food and breast milk is around 90% water. So this is instinctive, this sort of bulk drinking behavior, waiting for a signal of thirst before drinking to satisfaction. This was actually the norm, not constantly having water at our lips and in within reach throughout the entire day. So this fascinating idea from evolutionary biology is that our bodies evolved not with constant access to water, but with intermittent hydration. So you've, we've talked about intermittent fasting, now we're talking about intermittent hydration. Sounds extreme, bear with me and we'll get to my response to this at the end.
Dr Rupy: So in response to these regular periods of mild dehydration, what seems to happen is that our bodies develop a unique coping mechanism. So what happens when you're a little thirsty? Well, when we experience mild thirst, it triggers very specific physiological chain reactions. So thirst slightly increases the sodium concentration. It's not the thirst, it's the dehydration. Your sodium level concentration goes higher in the blood. This is labeled hypernatremia in the extreme sense and overall blood thickness very, very gently goes up. This isn't at the extreme, this is just what happens when you're a little bit dehydrated. You experience something called hyperosmolality. Now there are parts of the brain that are very sensitive to when this happens. They can tell when your sodium levels are going up and when your blood is becoming a little thicker. There's a region of the brain called the organum vasculosum of the lamina terminalis, the OVLT. It plays a key role in sensing and regulating salt and fluid balance in your body. And what this does is it activates two powerful hormones in the hypothalamus, oxytocin and vasopressin. Oxytocin is often called the love hormone. It doesn't just help with bonding socially, it also plays a surprising role in calming the nervous system as well. And both of these hormones, this milieu, this sort of chain reaction, it leads to calming the body by inhibiting the stress response, so suppressing the sympathetic nervous system and the HPA axis, which can reduce anxiety, reduce aggression, reduce fear, increase feelings of trust and bonding and help regulate cravings for things like salt and sugar. So it stimulates a natural desire for water without overdrinking.
Dr Rupy: So the overall effect is that our our usual stress systems are sort of dialed down. This fight or flight response, which is governed by the HPA axis and the sympathetic nervous system, is muted, as evidenced by cortisol levels reducing during mild thirst. And this is pretty remarkable because it suggests that being a little bit thirsty might actually help us stay calm and centered. And this neuroendocrine loop leads to optimal hydration without needing to constantly sip, sip, sip all day.
Dr Rupy: I want to talk about the flip side because chronic underdrinking, which I think most people are at risk of, or drinking on the other side, drinking way too much that you suppress your natural thirst signals. So for people who have those massive bottles of water and they're just constantly chugging water all day, this can actually disrupt your normal fluid balance mechanisms and activate stress related systems like the renin angiotensin aldosterone system, abbreviated to RAAS. And this persistent RAAS activation is associated with metabolic syndromes, high blood pressure, insulin resistance and other risk factors for things like obesity and type two diabetes. So the practice is not about reducing your total water intake. That's not what this ancient practice is about. It's about changing the frequency in the same way intermittent fasting isn't about overall reducing your calories, even though that's probably what many people need to do. It's not changing about, it's not changing the total energy intake in 24 hours, it's just changing when you choose to eat those calories. So this intermittent hydration is about changing the frequency and when you choose to drink, not the total amount of fluid that you drink in 24 hours. So the goal is to try and drink in response to thirst until satisfied. And that's why it's called intermittent drinking or intermittent hydration.
Dr Rupy: It's sort of like you're guided by mild thirst and then you have a full drink, so you have a bulk drink, and then you don't drink until the next thirst cue. So as a practical guide, what I'm experimenting with, and I would say this is an experiment for me because I'm just so habituated to always having a bottle of water with me and just constantly drinking because it's there. But I'm going to try drinking when I just feel thirsty and not preventatively. So in the morning, I kind of have a bulk drink anyway. I've fasted overnight, I haven't had any hydration overnight. I do feel pretty thirsty in the morning. I will tend to have 800 mils of water in one go. Yes, I go to the toilet afterwards for a couple of times over the next hour, but then I'll try and have another bulk drink around 11 a.m. or something like that. Wait another couple of hours, see if I feel thirsty, and then drink again. That's sort of how a practical guide to trying intermittent drinking or intermittent hydration could work.
Dr Rupy: Another feature of this is drinking until you feel satisfied, not beyond, noticing when swallowing becomes sort of effortful or less pleasant, and avoiding this grazing on water all day just in case. You just put away the water bottle for part of the day, especially when you are sedentary.
Dr Rupy: I'm going to talk about the caveat in a second, but there is another practice where there are occasional controlled periods without any water that might be beneficial. In the same way you have periods of complete fasting for 24, 48 hours that have been studied to potentially have benefits, there might be some benefit in mimicking this evolutionary stress of having zero water or zero hydration at all that kept our ancestors resilient and physiologically balanced. Just in the same way fasting has become popular and evidence based supported in health thinking as a strategic tool, thirsting could be another ancient practice that becomes popular in the future. Now, like I said earlier, I'm aware that most people would benefit from doing the opposite. They would benefit from drinking more total water per day rather than less. But this practice of having a timer when like you have a bulk drink might actually be an easy way to keep your fluid intake overall up. So it might be something you want to experiment with, but like I said, this isn't about reducing water intake over most of your days, it's more about when you choose to drink and not ignoring your thirst cues or overriding them by just constantly sipping throughout the whole day.
Dr Rupy: And again, another caveat because I know this is controversial suggestion or theory from ancient challenges, but it does not mean that you should be ignoring your body's need for water. If you feel thirsty, you should definitely be drinking water, especially in hot weather or during intense activity. This is not about dehydrating yourself or pushing yourself into discomfort. It's getting in tune with your body's natural signals and being led by them rather than overriding them.
Dr Rupy: And it does challenge the modern notion that we should be constantly sipping water all day. And sidebar, because I know I'm going to get asked about this, should we be drinking electrolyte enhanced water? So electrolytes are the minerals like sodium, potassium, magnesium, calcium, chloride that help regulate fluid balance, muscle contractions and nerve signals and blood pressure and all the rest of it. We'll do a deep dive into electrolytes another time, but in specific situations, absolutely. But for most healthy people, plain water is perfectly adequate. So adding electrolytes doesn't offer major hydration advantages unless you're under certain types of physical or physiological stress. So intense exercise, experiencing hot weather, lots of sweating, this is where I personally use an electrolyte myself. I just use a very cheap electrolyte powder that I buy on Jeff Bezos's shop and add that after I train. But other than that, I tend not to use it. In the summer, I will add salt and sugar to my water, but in very, very small amounts.
Dr Rupy: Ancient challenge number three, plant toxins. What if the very plant toxins that make plants bitter and spicy are actually low dose stresses, actually something that makes you stronger? So there's a bit of hyperbole there, but I wanted to lead in with this idea of plant toxins because I think there's a trend online to demonize all food. Kale is killing you, legume lectins are causing leaky gut, fruit fructose fries your brain or whatever slogans you've heard online. Let's unpack this a bit, right? So plants, they can't run from predators or hide from the sun, so they've developed chemical defenses. These are natural toxins to protect themselves from things like insects and animals and other environmental stresses, right? So, for example, the reason why I choose Exhale coffee is because they grow their coffee or they choose their coffee from high altitude crops that are experiencing the stress of the altitude, the stress of the sun, the stress of the the lack of mineral availability in the soil, and it produces a higher polyphenol coffee. Over millions of years, humans and animals evolved alongside these plants, and surprisingly, our bodies learned to benefit from these plant stresses.
Dr Rupy: And the issue in modern life is not that plants have these toxins and they're trying to kill us. It's actually the opposite. It's actually we don't eat enough of these plant compounds that have toxic effects because of something called hormesis that we'll unpack in a second. So if you look just again from an evolutionary lens, from an anthropological perspective, the diet of our ancestors was remarkably varied. There's a huge range of plants and herbs that they would have access to. And the diversity of food products that they consumed include eggs and crustaceans and fish and small mammals and occasionally a large mammal as well. And even today, if you look at modern hunter gatherers, they have like 400 plant species, hundreds are used for food consumption, and the remaining serve for herbal teas and natural medicines. Today, us in the more westernized environment or the developed environment, which is a bit of a misnomer, we have around 20 different plants contained in the average diet of modern humans. We just don't eat enough of these plant toxins. So this low nutrient variety is actually associated with several conditions and diseases, low food diversity is associated with allergies and asthma. So we need a lot more complexity in our diets. We need a lot more of these plant compounds, also referred to as polyphenols or phytochemicals, because they trigger something called the hormetic response or hormesis. This very simply is a small dose of stress that activates your own body's defense systems. In the same way, the stress of lack of food, the stress of lack of water, the stress of exercise activates your own body defense systems, plants do this as well.
Dr Rupy: And there is a key player in hormesis when it comes to food and other stresses, and this is something called NRF2. It's a master regulator of cellular protection. And when we activate this, NRF2 boosts your ability, your body's ability to detoxify harmful substances, reduce inflammation, and protect cells from damage. It promotes antioxidant production. NRF2 is a real master regulator. It's phenomenal. And there are phytochemicals that can directly and indirectly stimulate NRF2. Sulforaphane in broccoli sprouts or broccoli in general, cruciferous vegetables, curcumin in turmeric, resveratrol in red grapes, quercetin in onions and apples. You get the sort of sense that I'm looking at the full spectrum of different plants, mainly those colorful ones as well. These aren't nutrients in the traditional sense. They're sort of like molecular irritants that your body learns to respond to. It's like a biological workout for your cells. So the same people who are saying kale is killing you and lectins are horrible for you are probably, or should say the same thing about exercise. Don't exercise, look at what it does to your cortisol levels. Don't exercise, look at what it's doing to your muscles. Where any reasonable person knows who's had a look at a shred of science knows that it's the complete opposite. So really, really be careful about anyone that is fear mongering about food because of these chemicals, because it's the chemicals that are actually healthy for you.
Dr Rupy: In addition, obviously to the chemicals, these modern hunter gatherer societies that have a plethora of different plant compounds in their diet have a microbiome diversity that is higher than any other world population, probably due to immense food variety that they consume. And populations with higher microbial diversity usually have lower rates of cardiovascular disease, neurodegenerative disease, partially explained by the microbial element.
Dr Rupy: So how big a dose of these plants should we be consuming? Well, you don't need high doses or supplements of these products. The key is getting regular exposure, inverted commas, to a variety of color, bitter, pungent, spicy foods. Even small amounts eaten consistently, these can build up your internal resilience over time. And you've heard me say it many, many, many times on the podcast and on YouTube, BBGs. It's an easy way to get this variety in every single day. Berries, beans, greens, seeds and nuts every single day. They will give you a plethora of these different phytochemicals that have this hormetic effect, this mild stressing effect that makes you stronger. Think of it as sort of microdosing on nature's medicine cabinet. A little bit of bitterness, a little bit of spice, it can go a long way in keeping your body sharp, adaptive and stress resilient.
Dr Rupy: Ancient challenge number four, heat exposure. So from ancient fire pits to the Finnish sauna, heat was once part of daily life. And today, it's actually making a huge comeback with sauna. So the reality is, you know, is it overhyped or is it actually good for us? Well, let's think about it from an evolutionary explanation because we didn't have infrared saunas and we certainly didn't always have a Finnish style sauna. Humans evolved in hot climates, right? So we all come from the equator, from from Africa, originally. And staying active in the heat, gathering food, hunting in the stark sun was just normal. And unlike many animals, we cool down by sweating through our skin, which means we can actually keep moving even when it's hot. It means like if you've ever done a marathon and every fiber in your body is telling you to stop, you can still go and you can still maintain health as well. And the theory is that this ability may have shaped our biology over time. So when we expose ourselves to this heat today, just like in a sauna or getting hot and sweaty doing activity, we could be reactivating some of these ancient responses.
Dr Rupy: So if we look at the evidence around sauna, which is probably the most well studied, overall, it can promote cardiovascular responses that are similar to exercise. I'm going to pull up a diagram for the folks watching on YouTube so you can actually see this. And when we look at the mechanisms behind why sauna could potentially work, number one, it improves vascular function and heart performance. It dilates blood vessels and enhances blood flow and cardiac output. Number two, it activates your favorite buzzword of the wellness moment right now, heat shock proteins. It does actually activate these heat shock proteins. These kind of work like tiny repair workers inside your cells. They fix misfolded proteins, they clear out damaged proteins, they help your cells stay resilient under stress. There's mechanistic evidence that they might help prevent neurodegeneration, so potentially preventing things like dementia and muscle atrophy. And there are some observational research studies that show improved lifespan as well, correlated with this heat shock protein activation, these levels being higher. Another mechanism is it lowers inflammation and oxidative stress by increasing the activity of NRF2, which I should have said earlier, is nuclear factor erythroid 2 related factor, a bit of a mouthful, but that's why everyone calls it Nerf 2 or NRF2, which regulates your antioxidant and immune functions in cells as well. There's even a suggestion that it lowers appetite. So even mild heat, like spending a couple of hours in a 26 to 27 degree centigrade room, just like the Doctor's Kitchen studio on a hot day because we've got these floor to ceiling windows, this can raise your skin temperature and make you eat less. So around 85 to 100 fewer calories for every increase in degree centigrade. And it might work by changing the hormones like ghrelin and leptin that you find in the hypothalamus as well. And then mood as well. This is really interesting. A single session of whole body heat therapy has been shown to ease symptoms of major depression for up to two weeks afterwards. So there are all these adaptive mechanisms that could be providing stress and that response, that adaptive mechanism, that response to stress, that's where you get all these different benefits as well. And if we're looking at benefits, there are a few long term studies that show improved cardiovascular disease. So over long duration, higher frequencies of sauna have actually shown to be associated with 40 to 70% reductions in the risk of all cause mortality. There are potential benefits for other conditions like respiratory diseases, muscular disorders, mental health disorders, skin diseases, headache, pretty amazing just from spending some time in a sauna as well.
Dr Rupy: So you can sort of understand this hype, particularly in the longevity field of sauna and why everyone is showing their home sauna or jumping into a sauna or doing like a traditional sauna. And we do see these sort of activities amongst native communities as well, where they build some sort of heat source and they create a shelter and you jump into that shelter for a period of time and you, you know, some people do hallucinate. So there are lots of different extreme of this and I'd always exercise caution whenever you are trying one of these ancient challenges.
Dr Rupy: Now I mentioned right at the top of this, the natural way that we would have got really hot is just by doing activity in the heat. And it seems that doing both could actually give you some more benefits. So there's research showing that people who work out and then use the sauna a few times a week actually see better results in things like fitness and blood pressure and cholesterol than just exercising alone. So it's sort of kind of like putting your body through a double challenge, movement first and then heat or heat and movement, you know, hot yoga, hot boxing, these are all things that have proved really, really popular in this sort of this wellness sphere. And actually, in a randomized control trial from 2022, people with low activity levels and at least one cardiovascular disease who did an hour exercise regime, both sort of aerobic and resistant, followed by a 15 minute sauna session three times a week had considerably better improvements in a very strong marker of exercise tolerance called VO2 max that we've talked about on the podcast before, and blood pressure improvements and total cholesterol than the people who only exercised. So there is some benefit in this combination, although it is a bit extreme. If you've ever done a long workout and then done sauna or you've done something like hot boxing or hot yoga, it's super, super intense. So if you do have a pre-existing issue, especially if you have things like cardiovascular disease or blood pressure problems, alcohol use, real, real big things to be aware of if you are going to be doing any dose of this. And speaking of dose, this is another area just like all the ancient challenges that it's really, really hard to determine what is going to be the best dose for which person. But from the research, there is a pattern that is emerging that the minimum effective dose, so the minimum amount of sauna or hot activity, getting hot and sweaty that you need to do, seems to be around two to three sessions a week for 15 to 20 minutes at a minimum of around 80 degrees centigrade, which I believe, from doing my degrees correctly, it's around 175 degrees. I'm looking at video producer Mitch here as if he's got a calculator in front of him, but he does not. But there are some studies that suggest going up to four to seven sessions a week, each lasting around 20 minutes again, seem to show more benefits. So maybe, you know, the the the key is consistency, maybe the key is doing more, but there's probably going to be an upper limit of this as well.
Dr Rupy: So how can you start this practice today? Well, not everyone has a sauna for a starter. So this might not be the easiest thing for you to do as an ancient challenge, but the minimum thing is to make sure that you are sweating as often as possible. And the easiest way to do that is to exercise. I'd start small and increase as you adapt as well. If you do have access to a sauna, two to three sessions a week, around 15 minutes each and build up your tolerance as your body gets used to that heat as well. Breathe through your nose and out through your mouth to calm the nervous system. And if you can, use it after exercise because it stacks the benefits and feels great for recovery. I personally try and get a sauna once or twice a week, but the most important thing that I always do, relating to what we were just talking about earlier, is hydration, particularly before and afterwards, because let's be honest, you don't need to have a break during that exercise. You can sip water during that time. This is probably where I would ignore that ancient challenge that I was mentioning about earlier and actually just sip water as often as possible because no one wants to have a low blood pressure moment in an extreme scenario like being in the middle of a sauna as well.
Dr Rupy: Some interesting advice I'm about to give you is to not go straight into a cold plunge after doing sauna. I know it's really popular. I know lots of fitness gyms are set up for this now, but that from my reading of the research and from the folks that I've spoken to is not the correct way to get the most benefits for these extreme stresses. It might make you feel great and if you want to do that, absolutely go for it. But if you are trying to maximize the benefits for the time and stresses that you are putting yourself through, you don't want to go straight from a hot sauna into a cold plunge. The reason why is because you want your body and its adaptive response to kick into action. You want sweating to occur naturally without immediately cooling down afterwards because it is this this process of bringing your body back down to reality or its homeostatic state, its balance state, that's where the benefits occur. If you do this artificially, you're not relying on your internal stress response systems. You are relying on an external input to warm you up.
Dr Rupy: And that brings me on nicely to ancient challenge number five. So a bit like heat, our ancestors lived in environments with cold stress, ice water, grabbing your fish, chilly caves, winter winds. And the theory is that the body evolved systems to adapt to cold exposure to help early humans survive changes in temperature. So what do we mean by cold exposure? Well, the common belief is that it has to be a cold plunge or an extreme. And the idea is we wouldn't have had that many extremes. It would have been a general transition from cold environments to hotter environments over the seasons and from different terrains. It wouldn't have happened in an instant. But cold exposure is any method of exposing the body to temperatures that are lower than comfort levels and that's efficient or that's sufficient, sorry, for a cold exposure stimulus. And it can be just going outdoors in the winter while wearing a light coat, cold showers rather than an ice bath, various forms of cold water immersion for long periods of time where you're doing exercise in water, but it does not need to be extreme.
Dr Rupy: The mechanisms of cold exposure seem less clear than heat exposure, but it could work in a few key ways. So there is the cold shock response. So when you're exposed to cold, your body ramps up protective proteins like CIRBP, cold inducible RNA binding protein, and thioredoxin that show multiple protective effects against brain and heart damage by preventing cell death and supporting your innate antioxidant systems like glutathione peroxidase. I always struggle to say this, glutathione peroxidase, and this naturally cleans up your free radicals. I know people are supplementing with glutathione and glutathione IV or orally, but you will naturally produce this and one way to boost that is actually through this cold exposure mechanism as well. Another commonly touted reason for why cold exposure is good is because it increases brown fat activity. So we have two different types of fat largely, white and brown fat. We also have beige fat as well. But the cold exposure stimulates the conversion of energy storing white fat into energy burning brown or beige fat. These fat cells burn abundant glucose and fat to generate heat. So you are utilizing your energy stores to generate heat. And this increases your basal metabolic rate. If you've ever heard me talk about BMR or basal metabolic rate in a previous podcast, you'll know that the vast majority of the calories that you burn every single day are because of this basal metabolic rate. What you eat, the amount of protein you consume, the thermic effect of food, the amount of exercise you do, your non-exercise activity, so things like walking and fidgeting that I do quite a bit, these are all the minority of what contributes to total calories burned. So your basal metabolic rate is the biggest area and anything that can increase your basal metabolic rate, which also can include things like caffeine, coffee, spicy foods, is going to be a great thing. It can help with weight, obviously, blood sugar regulation. And in one small study with 17 healthy subjects, nine male, eight female, 10 days of mild cold increased BMR in both men and women. Mild cold, so you don't need to do anything extreme, you don't need to plunge yourself into ice baths, mild cold is all you need.
Dr Rupy: And because of this cold exposure, the third thing is you get cold tolerance. So I've met lots of people from the north of England where it is considerably colder than in London. And for some reason, these folks can just walk around without a coat on. And you know, I just thought it was because they were built different, but it's because they've become more tolerant to the cold, which is something that can actually happen. So when you're regularly exposed to the cold, your body just gets better at warming itself up by turning on the process of non-shivering thermogenesis. So this is where they're not shivering, which is why, you know, I'm shivering and they're not shivering. They have this non-shivering thermogenesis that is activated. And the more you do it, the more your cold tolerance improves. Some studies even show that people who work in the cold a lot, like Norwegian fishermen, can keep better control of their hands in cold water as well.
Dr Rupy: From a neurochemical point of view, cold exposure increases dopamine, norepinephrine and oxytocin, which is why it's potentially being used as another therapy for those who have low mood as well. It increases your sense of clarity, alertness and potentially improves mental health conditions. There is this trend of cold plunging that I've referred to throughout this that people are loving because of the sense of clarity, because of that alertness. It's, you know, one of my friends described it as having four espressos without the crash later on. And if this is the way in which you want to utilize that practice, absolutely, that's great. But prolonged cold exposure potentially has more benefits long term.
Dr Rupy: And there is also a suggestion that regular cold exposure might help build mental resilience, strengthening the brain areas linked to self-control, emotional regulation. People often report feeling more capable and mentally tough afterwards, potentially because the cold exposure reduces the body's fight or flight stress response and help activates this calming rest and digest side instead. So in short, it might help you feel calm when you're in pressurized environments.
Dr Rupy: But again, in the same way I said, don't go from a sauna into a cold plunge, don't go from a cold plunge straight into a sauna. We think cold plunges work colloquially because it makes us tough. But the real power actually comes in not how much you can endure, but how much your body responds afterwards. So this rewarming phase is just as important. When you've had this cold exposure and your body's cold, your body builds resilience by working to return back to its baseline. So it's increasing blood flow, it's activating mitochondria, it's strengthening the temperature regulation system. So it's important to let your body do the work. Let your body heat you back up. This is where the power comes. If you go from a cold plunge to a sauna, your body doesn't have to do anything. It's you're going from an extreme cold to an extreme hot place. You don't need to turn on those activating mechanisms. So it stands to reason that you won't be activating these ancient systems, these innate stress response systems that provide benefit because again, you're relying on an external input to warm you up. So what I've started doing is if I'm going to have a cold shower, which isn't a cold plunge, or I'm going to go from in into a cold environment without my coat, I'm going to allow my body to warm myself up. I'm going to rely on, you know, internal thermogenesis because that is where the resilience builds up, not by essentially putting myself into a sauna straight after I've had a cold shower.
Dr Rupy: So let's just address some of those common mistakes and and myth bust a bit. Do you get more benefits the longer you stay in a cold plunge? No. Less is more. Short bursts provide those benefits, but the long cold exposure has no added benefit. The over activation of cold shock proteins might even have negative effects. Does it always have to be a full body plunge? No. Cold showers, splashing of face in cold water, cold air exposure, like sleeping in a cold room or outdoors, these can all activate cold receptors. Can anyone do it? Well, individual tolerance varies. People with cardiovascular conditions or high stress may need a gentle gentler entry point, but yes, overall, I believe everyone can do this. Can you do it straight after training? Like I said earlier, don't jump straight into an ice bath straight after the gym. Cold after training might actually blunt the adaptive mechanisms that your muscles have. It could blunt muscle growth due to reduced inflammation and oxidative signaling as well, both of which are needed for recovery and those strength gains. So don't do this straight after training, leave a gap to allow your body to recover and then if you enjoy it, that's when you would want to do it.
Dr Rupy: And one of the key things is consistency. So if you're just doing a cold exposure once or twice a year, you're probably not going to get these benefits. There was a study that compared regular cold water swimmers to people who are active but not cold adapted. And the cold group had lower markers for heart disease, like reduced homocysteine and better cholesterol profiles because their bodies were adapting. So overall, it has benefits. The key is dose, timing, natural recovery and consistency. And you do not need to go extreme to get the benefits.
Dr Rupy: So there you have it. Those are five ancient challenges: fasting, thirsting, plant toxins, heat and cold. But the caveat is that you've got to remember that ancient lifestyles were super diverse. So even though we're drawing from human history, there is no single ancestral way of living. A hunter gatherer in the Arctic is going to be very, very different to the stresses or experiencing stresses differently to someone in equatorial Africa. Cold, food availability, sunlight, diet, hydration, these all vary massively. So these practices don't often look the same everywhere. And everyone is different, genetics, age, sex. I personally do not like cold plunging. Every time I've ever done a cold plunge, I get sick afterwards, but I love sauna. And you know, it all depends on how you respond to different things like fasting and cold exposure. Context matters. So if you are already stressed because you commute for hours a day, you have environmental exposures and toxins and all this different stuff, you're sleep deprived or you're unwell, adding more stress might do more harm than good. So really think about this in the context of your own life. And remember, these aren't replacements. So think of these as add-ons, not substitutes for a healthy diet, movement, sleep, social connection. The foundations of a healthy lifestyle are underpinned by social cohesion as well. So I definitely wouldn't be doing these things in isolation. And if you are going to dive into any of these, try and build a community around it. It's always amazing that I think the reason why sauna and cold plunging has become so popular is because people love to talk about it. And when you connect with someone who's doing something extreme, that therein lies some of the benefit and some people would argue the majority of the benefit as well.
Dr Rupy: And dose is everything. You know, as a medical doctor, I know that more is not always better. A high dose of antibiotic, a high dose of blood pressure medication, it's not always better. It's the right amount at the right time that makes these practices and any intervention helpful. So remember, you've got to titrate the dose of any of these challenges to meet your unique individual needs.
Dr Rupy: If you're interested more in the concept of metabolic flexibility, I highly recommend you check out this episode with Dr Adam Collins, who talks us through everything you need to know about your physiology and how you can adapt to fat and carbohydrate and switch between them. Go check it out.
Dr Rupy: Thanks so much for listening to this episode of The Doctor's Kitchen podcast. Remember, you can support the pod by rating on Apple, follow along by hitting the subscribe button on Spotify, and you can catch all of our podcasts on YouTube if you enjoy seeing our smiley faces. Review show notes on the doctorskitchen.com website and sign up to our free weekly newsletters where we do deep dives into ingredients, the latest nutrition news, and of course, lots of recipes by subscribing to the Eat, Listen, Read newsletter by going to the doctorskitchen.com/newsletter. And if you're looking to take your health further, why not download The Doctor's Kitchen app for free from the App Store. I will see you here next time.
