Benefits of Cold Exposure, Shivering & Brown Fat | Dr. Susanna Søberg & Dr. Andrew Huberman
00:00:00.000 | So it sounds like any form of cold to the skin that people register as what you call
00:00:10.800 | the cold shock or uncomfortable, like, oh, like this is kind of jarring, activates the
00:00:16.040 | brown fat.
00:00:17.040 | Do we know what the pathway is from cold receptors on the skin to the brown fat?
00:00:20.680 | I mean, how does the brown fat know that we're cold?
00:00:23.200 | Yeah, really good question.
00:00:25.200 | And it seems that I, I think that of course, in the future, we will know much more about
00:00:29.340 | these pathways.
00:00:30.340 | But what we do know is that the cold receptors will send a signal to our temperature regulating
00:00:35.040 | center in the brain, so hypothalamus.
00:00:38.480 | And that's going to be taking in this message.
00:00:42.640 | And we have so many cold receptors in the skin.
00:00:44.520 | So it's going to be very fast.
00:00:46.360 | As you can say, if you immerse the body into cold water, this is going to be so rapid.
00:00:51.820 | So it will have a rapid increase in neurotransmitters in the brain from noradrenaline, adrenaline
00:00:58.280 | cortisol, and which is not that much, but it's but it's still there.
00:01:02.320 | So you have this increase in noradrenaline, which will then immediately activate the brown
00:01:08.360 | fat.
00:01:09.360 | And because the you can say the activator is the most potent one, cold and noradrenaline,
00:01:15.080 | that's going to activate the brown fat.
00:01:16.080 | But there's also a direct pathway from the cold receptors in the skin to the to the brown
00:01:20.840 | fat, which really shows that if because of these different pathways, it shows that that
00:01:26.880 | it could be that this tissue to keep us warm, or was developed in our involvement as humans
00:01:35.520 | to keep us warm and to save us whenever the temperature on our skin varies just a little
00:01:42.000 | bit to keep us in that right homeostatic balance.
00:01:45.580 | So we don't get hypothermic.
00:01:48.660 | But also so we don't get hyperthermic, because it seems that the brown fat is also activated
00:01:53.800 | when we get warm on our skin.
00:01:56.180 | So it's also maybe a temperature regulator in our in our body, but the pathways is different.
00:02:02.380 | I think it's also a third pathway from directly from the muscles.
00:02:06.380 | So the brown fat is also activated, even though the muscles are starting to shiver.
00:02:12.140 | So there's an extra pathway that way to keep our, our temperature up.
00:02:17.660 | So muscles and brown fat are working together to to keep us warm.
00:02:21.040 | So we don't suffer too much in the in the cold water.
00:02:25.180 | Super interesting.
00:02:26.180 | And what I hear you pointing to is the existence of three parallel pathways.
00:02:30.460 | And this notion of parallel pathways comes up over and over again in biology, as you
00:02:34.060 | and I know, and I mean, I think it's important for people to know about because, as you said,
00:02:39.820 | so so eloquently, the when something is very important to our survival or end or evolution,
00:02:46.540 | the brain and body install multiple mechanisms for it, not just one.
00:02:52.060 | And and so it sounds like it's cold skin, cold on the skin, triggers and a response
00:02:58.360 | in the hypothalamus, which then activates brown fat, cold receptors in the skin directly
00:03:02.800 | to the brown fat, and then shivering in the muscle to the brown fat.
00:03:08.020 | I want to talk about brown fat in depth and learn from you more about brown fat.
00:03:14.180 | Before that, however, I want to ask about shiver.
00:03:17.920 | I've heard that shiver causes the release of succinate, which then activates the brown
00:03:26.260 | fat.
00:03:27.260 | Is it known whether or not inducing shiver is important?
00:03:30.500 | And when should people shiver?
00:03:32.900 | I mean, I've gotten into cold plunges and shivered while I was in there.
00:03:35.960 | And then I've also had the experience of getting into a cold plunge or a cold shower, then
00:03:40.860 | getting out when even standing outside on a warm day after swimming in a pool and then
00:03:45.540 | starting to shiver.
00:03:46.580 | So the shiver comes later.
00:03:48.020 | So how important is shiver?
00:03:49.420 | And does it matter when shiver happens?
00:03:51.260 | Yeah, it was shivering is good, because that increases your metabolism, and that's going
00:03:57.220 | to burn some calories in your body.
00:03:59.420 | You shouldn't be so afraid of shivering, I think, because the shivering, as long as you
00:04:03.300 | don't get too hypothermic.
00:04:04.740 | So if you don't, if you don't sit in the cold water for too long, and and what you just
00:04:09.780 | said by shivering after you get up, that is because of the after drop something called
00:04:14.820 | the after drop is when your core temperature decreases even after you get out of the cold
00:04:19.900 | water.
00:04:20.900 | And it always does that your body because it as soon as you get into the cold water,
00:04:26.300 | all your blood vessels is going to constrict because you need to keep your blood in your
00:04:32.140 | core and keep your vital organs warm.
00:04:35.700 | So as soon as you get up that those blood vessels will open again, and the warm blood
00:04:40.220 | would flow out and get colder and then flow back again into the core.
00:04:44.700 | And that's going to decrease the temperature in your core, of course.
00:04:47.460 | So that's the drop.
00:04:48.660 | So that's the drop.
00:04:49.660 | Yeah.
00:04:50.660 | I'm so glad you explained that.
00:04:51.660 | I've heard years ago, Wim Hof, I heard him talk about the drop.
00:04:55.140 | And I've heard colleagues of mine talk about the drop.
00:04:57.100 | But that's the first time I've ever heard it explained clearly.
00:05:00.020 | Let me make sure I understand this.
00:05:01.140 | So I get into cold water, obviously, I'm cold.
00:05:05.860 | Vessels constrict to keep blood near the center of my body, keep me alive.
00:05:09.980 | I get out, the warming up of my body allows those vessels and capillaries to dilate again,
00:05:17.460 | the blood goes out to the surface, but the surface is still cold.
00:05:20.860 | And so that blood is cooled.
00:05:23.600 | And then my core body temperature drops.
00:05:25.780 | And that's what you're referring to as the drop.
00:05:27.580 | And that's what induces shiver.
00:05:29.020 | Exactly.
00:05:30.020 | Great.
00:05:31.020 | And then, am I right in thinking that then the shiver activates brown fat, which then
00:05:33.980 | warms me up again?
00:05:35.220 | Yes.
00:05:36.220 | Got it.
00:05:37.220 | That's why you should end on the cold.
00:05:38.220 | We can get back to that.
00:05:39.220 | Let's talk about it.
00:05:40.220 | Yes.
00:05:41.220 | Ending on cold, it's what I refer to as, and what has now become known as the Soberg principle,
00:05:46.540 | which is a really important principle about the importance of ending on cold and not doing
00:05:51.860 | what I do, which is to get into a hot shower or back in the sauna, but we'll get back to
00:05:55.940 | that in a few minutes.
00:05:57.420 | So that's wonderful that you can explain that so clearly, because I think that shiver is
00:06:04.020 | something that a lot of people do avoid.
00:06:06.260 | People think, "Oh, I don't want the chattering of the teeth," and it feels like a loss of
00:06:11.500 | bodily control, which really it is.
00:06:13.540 | It's an autonomic response.
00:06:14.820 | Yes, but I don't think that people should avoid it that much.
00:06:18.340 | It's just like seeing shivering as a way of your body, it's training.
00:06:24.040 | It's training for all your cells, it's training for your muscles, it's training of your metabolism,
00:06:29.140 | and that's going to increase what's called the insulin sensitivity.
00:06:32.580 | So if you can, in your mind, get used to the thought of shivering, it's just like when
00:06:39.500 | you go exercising in the training center and get that feeling of like, "Oh, this is tough.
00:06:44.380 | Now it hurts a little bit."
00:06:45.380 | Yeah, it's going to hurt because that's what shivering also does, but it's just a different
00:06:49.780 | way of training your cells in your body.
00:06:52.100 | It's going to create what is healthy stress, it's called homesis in the cells.
00:06:55.900 | And the more you expose your muscle cells or your brown fat cells to these kind of healthy
00:07:01.580 | stresses, exercise, cold, heat, exposure, it's going to make them better at activating
00:07:07.900 | and also at keeping you healthy.
00:07:10.700 | So as long as the cells get exposed to this, it's going to keep them on its toes, you can
00:07:16.580 | say, because it becomes more robust, increasing these heat shock proteins and cold shock proteins
00:07:22.760 | in the cells to make you more robust for the next time.
00:07:28.340 | And that is also what happens when you go to the training center.
00:07:31.360 | And I keep drawing that parallel, because people today know more about, we know more
00:07:36.420 | about exercise and what that is going to do to your muscle cells.
00:07:42.780 | But the same kind of training is also what you do when you go out into the cold water
00:07:48.180 | and submerge into cold water, because that is just your cold training center, you can
00:07:52.900 | say that.
00:07:53.900 | And also your heat training center going into the sauna, because the cells are getting stronger
00:07:58.620 | with hormetic stress.
00:07:59.620 | So it's the same process, just different practices.
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