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Chapter 1: What are the health benefits of deliberate heat exposure?
Welcome to Huberman Lab Essentials, where we revisit past episodes for the most potent and actionable science-based tools for mental health, physical health, and performance.
Chapter 2: How does temperature affect body and brain during heat exposure?
I'm Andrew Huberman, and I'm a professor of neurobiology and ophthalmology at Stanford School of Medicine. Today, we are talking about the science of heat. Heat is a remarkable stimulus, meaning when we are in a hot environment, it has a profound effect on our biology. So we're going to talk about the science of heat and heating, both in terms of their mechanisms.
Chapter 3: What protocols should be followed for effective sauna use?
And as I know many of you are interested in the tools related to the use of heat, things like sauna, how often to do sauna, how long to be in the sauna, how hot to be in the sauna for particular goals and outcomes. We heat up two ways.
We heat up from the outside, meaning the things that we come into contact with, the clothing that we put on our body, whether or not there's heat in the room or whether or not it's cold outside or cold in a room. And we heat up from the inside. At every point across your entire lifespan, you have two distinct temperatures.
Chapter 4: What are the different types of saunas and their alternatives?
One is the temperature on your skin, what scientists call your shell. and the temperature of your core, your viscera, meaning your organs, your nervous system, and your spinal cord.
Chapter 5: How does sauna use impact cortisol levels?
It is vitally important to understand that you have those two temperatures and that your brain is constantly sending out signals to your body as to whether or not it should heat up or cool down, depending on the temperature of the shell. So anytime we're talking about heat, meaning deliberate heat exposure, things like sauna,
It's very important to understand not just the stimulus, how hot something is, how long you're in a sauna, et cetera, but the effect that has on your shell and on your core. If you can understand that, you can design protocols that are literally perfect for your goals.
A brief warning now and another brief warning later, anytime you're talking about heating up your body, you need to be very cautious because unlike cooling down where you have a fairly broad range of cold temperatures that you can go into before it's damaging to tissue, well, you don't get to heat up the brain and body very much before you start getting into the realm of neuron damage.
Neurons in the central nervous system, the brain and spinal cord, once they're damaged, they don't come back.
Chapter 6: What role do heat shock proteins play in health?
So hyperthermia is a serious thing to avoid. There's a very basic circuit, meaning neurons that exist in the skin, in the brain, and in the body that communicate with one another that allow you to heat up if you need to and cool down if you need to. Once you understand this circuit and the way it's structured, then you are going to be in a great position to use the tools related to heating.
So here's how this circuit is structured. You have this shell, which is basically skin.
Chapter 7: How can sauna exposure increase growth hormone levels?
And within the skin, you have neurons, nerve cells. Those nerve cells have channels or receptors on them. They're called trip channels. There are some other ones as well, which basically sense changes in heat.
So if I were to put a hot object on your hand or your arm, or for instance, if I were to put a hot object on your hand or arm and then remove that hot object, those neurons would respond to that. They would send electrical signals into your spinal cord. And that's where the next station of the circuit resides.
Chapter 8: What are the optimal timing and hydration strategies for sauna use?
In your spinal cord, you've got a little cluster of neurons that exists at the top part of your spinal cord. called the dorsal horn. The name again, doesn't matter. And those neurons specifically relay heat information up to another area of your brain. Now here's where we get into some fancy names. It's the lateral parabrachial area.
You don't need to know lateral parabrachial area, but it's a relay station. The lateral parabrachial area sends electrical signals to the POA. And I would like you to know POA. The POA stands for preoptic area. Neurons in the preoptic area basically reside over the roof of your mouth. These are neurons within the hypothalamus.
And neurons in the preoptic area have the ability to send signals out to the rest of your brain and body to get you to heat up and actually to change your behavior. So there are all these different mechanisms by which we dump heat. Some of those are purely physiological. Below our conscious control, things like sweating, which you can't just make yourself sweat on demand.
Maybe you can through a set of stressful thoughts, but you can't just make yourself sweat. That is autonomic. It's below your conscious control. Things like vasodilation, the dilation of your veins in particular and capillaries in particular. And of course there are these behavioral, somewhat voluntary aspects of dumping heat.
And the lethargy, the kind of tiredness that we feel on a really hot day, that's also controlled by this circuit that I just described. The impulse to get yourself out of a very hot environment is the consequence of the POA communicating with your amygdala.
And the amygdala then in turn activating your adrenal glands, which sit right above your kidneys, the release of adrenaline, and this feeling of agitation like you want to move. Usually you want to move out of whatever hot environment you happen to be in. So now you know the circuit. Again, it's simple. It goes from skin to spinal cord, one brain area to another brain area.
That's the key one in this discussion, which is the POA, the preoptic area. If you can conceptualize that circuit, or if you can even just understand what I just said, even at a top contour level, you're going to be in a great position to understand the rest of the information and the tools that follow. As many of you know, I've been taking AG1 for nearly 15 years now.
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