Cold vs Hot: Which is Better for Women? | Dr. Stacy Sims & Dr. Andrew Huberman

00:00:00.000 | cold. Yeah. For reasons I still don't understand, people have associated me or this podcast with

00:00:08.940 | deliberate cold exposure. I like deliberate cold exposure in the form of a cold shower or a cold

00:00:13.320 | plunge or an ice bath, mostly for the effects that occur afterward. Oh yeah. Yeah. And every

00:00:20.100 | time I do a post about deliberate cold exposure, I get asked, understandably so, how does it affect

00:00:26.480 | women differently than men? I prefer heat for women. Everyone's a responder to the heat. You get

00:00:31.800 | better adaptations. So sauna? Yep. Sauna. Hot tub? Yep. Preferably a true finished sauna. Infrared

00:00:39.220 | doesn't, it warms the skin, but not the core. Thank you for saying that. I'm not a big fan of

00:00:43.720 | infrared sauna because it doesn't get hot enough. No. Yeah. You can bring an infrared light into a

00:00:48.240 | traditional sauna if it can tolerate the heat. Yeah. So the thing with cold water exposure is

00:00:53.120 | the whole conversation about ice cold, ice baths and how cold it is. It's too cold for women because

00:01:00.920 | when we're looking at that severe immediate jump into that icy cold, it causes such severe constriction

00:01:09.100 | and shutdown. So women do really well and get that whole dopamine response and everything. If the water

00:01:16.480 | is around 16 degrees C, which is 55 to 56 degrees Fahrenheit. Which is chilly. It's chilly. It's not

00:01:24.340 | warm. No. It's go dive in San Francisco Bay, right? And that is enough to offset that severe constriction

00:01:33.120 | survival, but it is cold enough to invoke all the changes that we want with cold water exposure.

00:01:42.160 | So it's a temperature nuance that sets sex difference. And like I said, when I have open

00:01:48.560 | water swimmers who are going to do a long swim or they're going to do a triathlon and the water is

00:01:54.620 | colder, I have them do cold water exposure, especially face exposure into the cold water to get them

00:02:01.820 | habituated to that initial severe constriction and sympathetic activity that we don't want to happen

00:02:09.780 | before a race. With heat being the true heat that we're talking about with sauna, we see a lot of

00:02:18.180 | metabolic changes for women. So we're having better insulin and glucose control. We're seeing a better

00:02:26.360 | expression of our heat shock proteins and the uncoupling and the rebuilding of those proteins that are

00:02:33.620 | cardiovascular responses. And then for women as we get older and have the offshoot of hot flashes,

00:02:42.660 | night sweats, that kind of stuff. If you're doing heat exposure, you're sending a stronger stimulus to

00:02:49.800 | the hypothalamus and you're also getting a better serotonin production from the gut because we have

00:02:57.200 | 95% of our serotonin produced from the gut, which lends to better temperature control and shuts down

00:03:03.880 | hot flashes. So it's not that you disapprove of using deliberate cold exposure. You just recommend

00:03:09.180 | that women do deliberate cold exposure with temperatures that are maybe in the low 50 degree

00:03:15.180 | Fahrenheit range as opposed to the really, frankly, just painfully cold for anybody, 38 to 50 degree

00:03:27.660 | temperatures. I've been asked whether or not pregnant women can do deliberate cold exposure probably no

00:03:35.140 | fewer than 2,500 times on social media. And I never have an answer, but I always default to the cautious answer,

00:03:44.980 | which is, uh, please don't until you talk to somebody who actually has an answer. Yeah.

00:03:48.940 | Just because it sounds like a very precarious situation, but in all honesty, I don't know.

00:03:52.880 | I'm just biding time there and just saying, please go ask somebody who can give you a definitive answer.

00:03:57.320 | Yeah. So we see women who have a high risk for miscarriage, that anything that they do that's

00:04:02.940 | incredibly stressful for the first 12 to 20 weeks will put them at a higher risk for it. So being very cautious,

00:04:12.380 | especially with cold, because we know that there are so many different nuances doing something like hot

00:04:18.220 | yoga when you're pregnant is not, there is research. So it's not detrimental because, yeah,

00:04:24.220 | because when we're looking at blood flow diversion that way, when you have slight hypoxia to the placenta

00:04:32.500 | and to the baby, there is a rebound effect that increases the vascularization so that the baby has better nutrients.

00:04:42.520 | We see this also with like exercise and exercise intensities. This is why people are now saying you need to

00:04:48.340 | have some kind of blood flow change and increase in core temperature to create these vascular effects

00:04:54.020 | effects within the placenta to improve nutrient and nutrient delivery to the developing fetus. So

00:05:01.620 | heat's good. Cold, I'm not so sure of.

00:05:04.500 | But probably not extreme heat.

00:05:05.880 | Not extreme heat. So that's why I mean like hot yoga is not going to the sauna. Hot yoga sits around

00:05:11.840 | 40 degrees Celsius. So what is that? Just around 100 degrees Fahrenheit.

00:05:16.360 | And in that situation, if you're feeling too hot, you leave, you lie down on the floor, don't try to stay

00:05:23.960 | for the whole class. But it's not going to be detrimental unless you're pushing yourself too much.

00:05:30.200 | Again, everything in moderation, especially when you're pregnant.

00:05:32.840 | It's almost the inverse of what we know for males, which is if men want to conceive, they should avoid the

00:05:40.840 | sauna because we know that heat is detrimental to sperm viability in a real way. So much so that

00:05:48.120 | I tell guys, if they are trying to get their partner pregnant, that they should bring an ice

00:05:53.640 | pack into the sauna. They should insulate that ice pack. Don't put it directly on the scrotum

00:05:57.960 | for other reasons, but that it's a, you know, that the effects of heat, the negative effects of heat

00:06:02.920 | on sperm are real. But there's also an interesting, it's not just a trend. There's actually some research

00:06:07.880 | showing that cooling the testicles leads to increases in testosterone, which is on the face of it kind of

00:06:18.040 | counterintuitive because it turns out that it's about the vasoconstriction causing the subsequent

00:06:27.160 | increase in blood flow, increased vasodilation. So the inverse of what you just said, which is that

00:06:33.320 | during the heating process, the hypoxia induces more vascularization of the placenta. So when

00:06:39.880 | talking about temperature, one always has to think about the surface of the body versus the brain

00:06:43.400 | response, as we talked about earlier, and then what's happening during the deliberate heat or deliberate

00:06:47.560 | cold versus what's happening after the deliberate heat or deliberate cold, right? Everything in biology

00:06:52.920 | is a process, not an event. Yeah. And I should make full disclosure. I started as an environmental

00:06:57.800 | exercise physiologist and my PhD was all in heat and heat research. So I'm a little bit biased towards

00:07:04.360 | heat, but I've done a significant amount of research in the hot and cold. Thank you for the disclosure.

00:07:10.360 | Yeah. I see it more as an indication of real knowledge. So thank you. This is an aspect of your

00:07:16.280 | training I knew a little bit about based on your publications, but I didn't realize the depth of

00:07:19.880 | knowledge. So we're all benefiting here.

Cold vs Hot: Which is Better for Women? | Dr. Stacy Sims & Dr. Andrew Huberman

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