How Long to Sauna & Cold Plunge for Key Benefits | Dr. Susanna Søberg & Dr. Andrew Huberman
00:00:00.000 | - What were the thresholds that you discovered
00:00:05.000 | were important for getting these positive changes
00:00:08.780 | such as reduced blood sugar or clearance of blood sugar
00:00:13.900 | being more efficient, reduced insulin,
00:00:17.080 | improved brown fat distribution and density?
00:00:20.680 | How much cold exposure do people need?
00:00:23.480 | How much heat exposure do people need
00:00:25.200 | in order to extract these benefits?
00:00:27.800 | - Yeah, so when we then calculated the numbers together,
00:00:30.800 | we could see that this was ended up being 11 minutes
00:00:33.960 | in total per week.
00:00:36.120 | So not in one session, of course,
00:00:37.720 | but they had two to three visits
00:00:40.400 | to the water and the sauna per week.
00:00:42.820 | So when we divide that out,
00:00:44.980 | it corresponds to being in cold water
00:00:47.080 | one to two minutes at a time,
00:00:48.940 | but also in the sauna 10 to 15 minutes at a time.
00:00:51.920 | And I think this is very like also similar
00:00:54.920 | to what we see in other studies
00:00:56.880 | when we look, for example, to the observational studies
00:00:59.920 | from the Finnish cohort study from Lauken et al.
00:01:04.240 | For example, they published this very amazing paper in 2015.
00:01:09.140 | Some results from this long cohort study
00:01:11.480 | where they show that up to 30 minutes in the sauna
00:01:16.480 | was healthy and you lower your risk of cardiovascular disease
00:01:21.880 | and that's like the threshold.
00:01:23.240 | And if you go further than that,
00:01:25.120 | then there is not more healthy benefits to gain from that.
00:01:30.120 | So, and before that, it's like 19 minutes,
00:01:33.920 | then you will have this dose response relationship
00:01:36.720 | up to 19 minutes.
00:01:37.880 | That's really in decreasing your risk
00:01:40.320 | of cardiovascular diseases.
00:01:42.360 | And I think-
00:01:43.200 | - That's per week, 90 minutes per week.
00:01:45.560 | - 90 minutes per session now.
00:01:47.200 | - Per session.
00:01:48.040 | - Yeah, per session.
00:01:48.880 | If we then compare that with my study,
00:01:53.920 | which was 10 to 15 minutes per session,
00:01:57.240 | then I think it fits very well
00:01:58.680 | with what we call the hormetic stress or healthy stress.
00:02:02.020 | So you expose the cells to this kind of like
00:02:04.520 | potent, very stressful situation
00:02:07.440 | where they increase heat shock proteins in the cells
00:02:10.420 | and that will repair the cells.
00:02:12.120 | But if you then overdo it
00:02:14.040 | and you go beyond the maybe 30 minutes in the sauna,
00:02:17.640 | this observational study from Finland
00:02:20.460 | with more than up to 2000 sauna bathers
00:02:24.180 | where they followed these for 20 years,
00:02:26.260 | they see that 30 minutes per session is like enough.
00:02:30.040 | And if you go above that,
00:02:31.520 | you don't get more health benefits out of it.
00:02:33.820 | So I think there's a window where we can say
00:02:36.000 | the healthy stress corresponds to like 10 minutes.
00:02:39.460 | And I think it's like-
00:02:40.300 | - Per session.
00:02:41.120 | - Per session.
00:02:41.960 | And it's not much actually.
00:02:43.880 | So you don't need to,
00:02:46.020 | it shows that you don't have to expose yourself
00:02:48.020 | very much to the heat or very much actually to the cold
00:02:51.420 | to get this healthy benefits from going into cold,
00:02:55.380 | going to heat and have healthy benefits
00:02:57.140 | on your cardiovascular system.
00:02:58.580 | So I think this is very important also message to get out
00:03:02.540 | that you don't have to go extreme.
00:03:04.900 | You don't have to swim for a half an hour in the cold water.
00:03:08.800 | You can go in the water for one to two minutes per session,
00:03:13.400 | but go up to 11 minutes per week in total.
00:03:17.020 | And for the sauna,
00:03:18.500 | my study showed 57 minutes in total per week.
00:03:22.740 | And if we also then divide it out on these two to three days
00:03:25.940 | and two sessions each day correspond to 10 to 15 minutes.
00:03:30.100 | So it's a low threshold,
00:03:32.020 | but I think it's good to have that
00:03:34.860 | to maybe we can aim for that
00:03:37.140 | if people needs to have something to aim for.
00:03:39.820 | And I think it's really good to have that
00:03:42.120 | because then you don't overdo it.
00:03:45.940 | And if you overdo it, you exhaust the cells
00:03:47.900 | and that will increase your risk
00:03:49.940 | of cardiovascular disease also, so.
00:03:52.820 | - Well, I get a lot of questions about this
00:03:54.420 | and I did solicit for questions for this podcast on Twitter.
00:03:57.540 | And one of the questions that I got was
00:03:59.340 | as one becomes more cold adapted,
00:04:01.460 | do the benefits start to wear off
00:04:03.140 | or can people do too much cold exposure?
00:04:05.540 | Of course, the answer to that is yes,
00:04:06.900 | you can become hypothermic,
00:04:07.960 | but I'm sensing a different answer now,
00:04:11.060 | which is if I understand correctly,
00:04:13.620 | the threshold is 11 minutes total per week
00:04:16.100 | of deliberate cold exposure
00:04:17.460 | divided into two or three sessions
00:04:19.860 | of maybe one to three minutes,
00:04:21.220 | depending on how long somebody stays in.
00:04:23.300 | And then 57 minutes,
00:04:25.940 | I want to be careful not to round up to an hour,
00:04:29.360 | but divided into maybe three 20 minute sessions or so,
00:04:33.060 | so one doesn't have to be perfect
00:04:36.420 | as long as you get beyond that threshold.
00:04:38.780 | But I wonder something, which is,
00:04:42.660 | is it the case that if somebody said,
00:04:44.140 | oh, I'm just going to do one 11 minute session per week,
00:04:47.900 | that might actually not be as beneficial as dividing it up
00:04:52.580 | because what you told us earlier
00:04:54.500 | is that the hormetic response
00:04:57.080 | depends on having that cold shock.
00:04:59.060 | You actually don't want to become too cold adapted.
00:05:01.220 | I mean, once the blood pressure response drops down,
00:05:04.360 | so in minute four, five and six,
00:05:07.020 | you're getting very cold and you're shivering,
00:05:08.700 | but one is not getting the autonomic stimulus
00:05:12.340 | that they want.
00:05:13.180 | I guess I could liken this to if exercise worked in a way
00:05:16.540 | where it was only the first few minutes of exercise
00:05:19.260 | that really triggered the adaptation.
00:05:20.640 | Of course, this is not how it works,
00:05:22.140 | but in fact, probably quite the opposite.
00:05:24.460 | But if that were the case,
00:05:26.740 | then it's not simply the total amount of exercise,
00:05:29.460 | but dividing up the sessions into little bouts
00:05:33.780 | where every single time it acts as a stimulus.
00:05:36.920 | That seems to be the key here.
00:05:40.040 | - This is very important
00:05:41.560 | because having watched the landscape of this on social media,
00:05:44.760 | but also in books and generally,
00:05:47.680 | I think you're the first person to really touch on this,
00:05:50.240 | that the goal is not to get so cold adapted
00:05:53.220 | that you can sit in for the full 11 minutes in one session,
00:05:56.200 | where the goal isn't to be able to do an hour
00:05:58.200 | of very hot sauna.
00:06:00.120 | If you want to, I suppose people could do it
00:06:01.640 | for other reasons,
00:06:02.480 | but if the goal is to improve these health metrics,
00:06:05.720 | then the idea is to keep the stimulus a stimulus.
00:06:09.600 | Short, exactly, yeah.
00:06:11.880 | - Great, well, this also,
00:06:13.880 | I think there's practical feasibility, as you pointed out,
00:06:16.180 | 'cause getting into a cold shower or cold immersion
00:06:18.880 | or natural body water for a couple of minutes
00:06:21.400 | is far less challenging to most people
00:06:25.800 | than finding a full morning to go spend there.
00:06:28.820 | But I've never really heard it articulated
00:06:32.860 | that the longer sessions might not be beneficial
00:06:36.560 | and might actually be detrimental.
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