Dear Mark: Saunas and Finnish Longevity, Saunas and Sperm, What About Ambient Temperature?

For today’s edition of Dear Mark, I’m answering three questions from readers. There was some good feedback after last week’s sauna post, and I want to address a few of the comments. First, does the fact that Finns don’t live as long as some of the other more storied “blue zone” populations despite using saunas negate the utility of the sauna? Second, what should we make of the recent study showing negative effects of sauna on sperm health? And third, isn’t it more “natural” and Primal to seek out smaller ambient temperature fluctuations, rather than brief exposures to extreme temperatures?

Let’s go:

Lots of Finnish references but the Fins are not one of the Blue Zone populations. Of the 5 BZ populations, the Okinawans may use a sauna/hot springs – not sure about the the other 4 though.

Finnish men do have the lowest life expectancy among Nordic countries. It’s still pretty good globally—84 years for women, 79 for men—but for being in one of the more developed areas of the world, it’s not great. Yet they use saunas, a supposedly life-extending practice. What gives?

The biggest killers of Finnish men are diabetes, heart disease, and alcohol. Some combination of diet, genes, environment, and lifestyle are contributing to those deaths—that’s what the Finns are up against. Most of the Blue Zones don’t have these issues:

They tend to be in milder climates with better access to sunshine.

They have lower levels of social isolation than Nordic countries like Finland.

They have more “longevity genes” than other areas. The Blue Zone Sardinians, for example, are the subjects of a major ongoing study into the genetics of longevity.

To say nothing of the diet differences.

Sauna usage may very well be keeping life expectancy higher than it should be, given the other risk factors. Research indicates that using a sauna 4-7 times per week confers a 40% reduction in all-cause mortality and even greater reductions in heart related deaths among middle aged Finnish men, which is the cohort most at risk of dying. These numbers, coupled with the numerous protective mechanisms outlined in the last sauna post, lead me to believe that saunas are helping, not hurting Finnish mortality.

Stefan pointed out:

One conundrum is that daily sauna use will sabotage your ballsack precisely because of the heat. Check this old nut-of-a-study:

Sadly, yes. This is a real issue.

What happened in this study?

10 men were recruited to participate. They were in their 30s, generally healthy, and, at baseline, had normal sperm parameters. For 3 months, they each used the sauna at 80-90?C twice a week for 15 minutes per session. Sperm parameters were tested at the start of the sauna use, after 3 months of sauna, and at 3- and 6-months post sauna. They included:

Sex hormones (testosterone, estradiol, FSH, LH, sex hormone binding globulin)

Sperm count (absolute number of sperm)

Sperm motility (ability of sperm to move independently and perform necessary functions)

Sperm histone/protamine ratios (indicative of sperm quality; smokers’ sperm more likely to have dysfunctional ratio, for example)

Sperm mitochondrial function

After three months of sauna, almost every parameter was negatively affected. Sex hormones remained the same, but sperm count and motility were greatly reduced. The proportion of sperm with dysfunctional histone/protamine ratios increased. Sauna increased the number of sperm with poor mitochondrial function. Luckily, everything returned to normal 6 months after sauna use stopped. But still, that’s a big effect.

This seems like a strong mark against using saunas when you’re trying to conceive. The doses were realistic (15 minutes a day, twice a week) and the effects significant. Not only do saunas appear to lower sperm count and motility, they may decrease the genetic fitness and quality of the surviving sperm. This could increase the risk of miscarriage and even have long term effects on the offspring,

If you’re an older guy uninterested in conceiving, this study shouldn’t affect your sauna habits. Sauna doesn’t affect your sex hormones, which have an outsized effect on the quality of your life. It just reduces the viability of your sperm.

If you’re a younger guy interested in having kids, don’t ignore these results. Avoiding saunas for 3-6 months before trying to conceive might be a good idea.

So, in the name of being seasonal and living naturally, what about just getting out in the heat (and not having an air conditioner–but yet cooking a lot) in the summer and being out in the cold in the winter and keeping the house temp low? Is that enough heat/cold exposure to have beneficial effects? (Might be harder to study.) Instead of taking the time to do something extra that takes up natural resources to create, get the exposure through living. Spend half the year hot and half the year cold. (Plus the cold exposure of going to the grocery store in hardly any clothes in the summer, and the heat exposure of going to someone’s house or the local school dressed for cold in the winter.) (Of course this only works in places that have different weather in the seasons.) Isn’t that more along the lines of Grok-ness?

This is ideal, yes. It’s a great point.

There’s actually some evidence that exposing oneself to cold and hot ambient temperatures, rather than maintaining a steady 70º at all times, is good for us.

As I pointed out in an older post, the general trend is that the more people are exposed to predictable, constant ambient temperatures through central heating, the more likely they are to gain weight. In mice, keeping all other variables (diet, activity, etc) the same while switching to a “thermoneutral” ambient temperature (the temperature at which organisms can maintain body temperature without expending any extra energy) triggered inflammation, increased atherosclerosis, ruined blood lipids, and made the mice obese.

Mild cold exposure (just a few degrees’ worth) was enough to activate brown fat (the metabolically active form that kicks in to keep us warm, burning calories in the process) in people. They achieved it by setting the thermostat a bit lower than normal—nothing extreme like ice baths.

I see saunas and cold baths as extreme stressors that address extreme deficiencies. Just like intense workouts can mitigate the effects of sitting around all the time and failing to get the constant low-level movement our physiologies expect, intense heat or cold exposure can mitigate the effects of indoor climate control. But they’re probably not enough. It’s probably better—and certainly more Primal—to also keep the heat down in the house, walk around in the cold in short sleeves, and get comfortable with hot weather.

One thing I’ve been experimenting with is limiting the amount of time I use the AC. I’m trying to just deal with hot days, whether by walking around in as little clothing as possible or creating air flow with open doors and windows. AC has always felt”stale” and “artificial.” I still use it when it’s unavoidable, but I’m beginning to almost enjoy the sensation of low level heat.

That’s it for today, folks. What’s your take on all this? Anyone conceive despite using the sauna? Anyone else trying to vary the ambient temperature in their life? Let me know down below.

Thanks for reading!

Tanskanen J, Anttila T. A Prospective Study of Social Isolation, Loneliness, and Mortality in Finland. Am J Public Health. 2016;106(11):2042-2048.

Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015;175(4):542-8.

Garolla A, Torino M, Sartini B, et al. Seminal and molecular evidence that sauna exposure affects human spermatogenesis. Hum Reprod. 2013;28(4):877-85.

Giles DA, Ramkhelawon B, Donelan EM, et al. Modulation of ambient temperature promotes inflammation and initiates atherosclerosis in wild type C57BL/6 mice. Mol Metab. 2016;5(11):1121-1130.

Chen KY, Brychta RJ, Linderman JD, et al. Brown fat activation mediates cold-induced thermogenesis in adult humans in response to a mild decrease in ambient temperature. J Clin Endocrinol Metab. 2013;98(7):E1218-23.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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20 thoughts on “Dear Mark: Saunas and Finnish Longevity, Saunas and Sperm, What About Ambient Temperature?”

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  1. Great questions. I live in PA, so I deal with pretty extreme temps on a seasonal basis. Today it’s in the 90’s with high humidity. Winters are cold, snowy and windy. I walk my dog (who seems to enjoy every kind of weather) in all of this. So far I haven’t really gotten into the cold immersion thing at all, except sometimes ending my shower with a blast of cold. Same thing with the heat…enjoy an infrared sauna every now and then, but nothing I’ve done on a regular basis. Based on the third question I’m feeling pretty good about my routine:)

  2. Mark, please write about cold laser/deep tissue laser therapy. I have enjoyed your posts about red light. This is something more, which has helped me tremendously.

  3. I live in PA as well and do not own an air conditioner. While I dislike the hot, humid summers, they have not killed me, though I don’t sleep as well when the temp in my house is 90 degrees at 11 p.m. I work from home and get by with a large “cyclone” fan going in my office and two of them in the bedroom at night.

    Growing up poor here as a kid in the 1950s, we used fans, cold sponge baths and cross breezes in the house to get through the hot summers. We put on extra clothes in the house in winter to keep the heating oil bills down. The thermostat was never set higher than 67 degrees and usually it was on 65. The heat got turned off at night. If, as kids, we complained, we were told to put on another sweater/pair of socks or we were given another wool blanket for the bed. No matter what time of year, we always slept with a window open in the bedroom.

    While it is undeniably pleasant to sit in an air conditioned movie theater or shop in a temperature controlled grocery store, I most enjoy the varying temperatures of each season and I love the winters here.

  4. The negative side effects of sauna are something I am especially interested in. I enjoy the sauna and outside of the array of different benefits I relish the feeling of a good sauna session. But unfortunately I have a condition called varicocele that gets exacerbated by sauna use.

    Varicocele is an enlargement of the veins within the scrotum, similar to the varicose veins many women have. A varicocele causes a handful of issues for men with the condition—exactly the issues that you stated above—reduction in hormones, sperm count, and sperm mobility. I likely had a slight genetic predisposition to the condition, but the root cause was my terrible and habits when it came to my diet and lifestyle.

    Fortunately I have been able to largely mitigate these issues and drastically improved the grade of my varicocele as I have lost weight and improved my health and eating habits (which I owe you many thanks for Mark!). Having a varicocele gives me a very finely attuned sense of when something is causing stress to my boys, which is a bit weird, but kind of useful in situations like this one.

    I have always “felt” that the sauna might have some of these negative side effects, it’s good to see this issue getting talked about a little bit more. Sauna’s are great on so many fronts, but everything in health exists on a spectrum, nothing is black and white.

    I plan to continue using the sauna, but will likely restrict my usage to really opportune moments, like post weight lifting for HGH secretion. I would be curious to hear others thoughts. Is the sauna beneficial enough where it is still worth it even with the negative side effects?

  5. Really interesting, I’m in the UK, so we have some temperature fluctuations and most homes don’t have AC, as it’s not often hot enough to warrant it. This year we have had a very cold winter followed by a very hot summer too the house was very warm inside, even at night. Interestingly, as a student in the North of England, 20+ yrs ago, we had no central heating in our house, just gas fires, so in the winter it was cold inside until the fire had warmed up the room. I remember having no colds or rhinitis at all, it definitely felt healthier, although sleeping in all your clothes on a cold night was not exactly comfortable.

  6. “Enjoying the sensation of low-levet heat”
    I see Miami’s finally getting into your brain! Wait for while and you’re going to start paddleboarding with the sharks.

  7. I live in the rural South, in TN, and highs have been in the low 90s for weeks, with high humidity. I work outside for an hour or so every day, usually early or late. I don’t use AC much except for an hour or so in the late afternoon, mostly to dehumidify the house. I have adapted to heat over the years, but it is a bit stressful. When you are pouring sweat while typing, you know it’s humid. It’s more the humidity that is stressful than the actual heat.

    I also keep the house pretty cold in winter, around 60. I use wood heat with a heat pump back-up. To save time and money, sometimes I don’t use either. I wear a wool cap inside and wool socks.

  8. Regarding sauna risks, this begs for a new product. ‘Sack Saver’ or ‘Codpiece Cooler’ or perhaps ‘Boyz in the Fridge’

  9. During our brutally hot summer in Massachusetts (I know you Florida people will say yours was hotter, but it’s Massachusetts!) I got out into the sun for an hour or two every day at mid-day and then went back inside to the AC to get back regulated. I’m not sure if it helped in terms of hormetic stressors, but I’m really tan 🙂

    Side note, I slept in AC as much as necessary because I rank sleep quality above pretty much anything else. Again, not sure how this works in terms of what the research supports, but I slept well 🙂

  10. Southern Arizona for me where summer temps are routinely above 110, I also work outside as a field biologist and I always relished building my “heat tolerance”, I literally can’t stand how air conditioned and freezing every building is though….

  11. Before we moved I used to use a hot-rock dry sauna to get rid of colds. It typically raised my body temp by 5 degrees in 30-40 minutes. Afterward I’d bundle up and watch TV for an hour to keep the heat in a little longer. There’s no mistaking the startling feeling when that heat boost to the immune system kills a cold. Saunas killed my colds only about half the time but those results were good enough that I always tried. I should note that the temperature of my balls was not a concern.

  12. I’m a cyclist. In the summer, I will regularly spend a few hours exercising in whatever the heat is (70-95 or so).

    I ride in the fall/winter/spring as well, and being cold is just part of the scenery; you are going to get cold while you are exercising. I find that I’m better on low carb if it’s a little chilly.

  13. Studies show that cold homes increase blood pressure. This may help explain why the UK has 30,000 to 40,000 excess deaths per winter. There’s a recent UCL report on this. Living at 25 instead of 15 degC seems to have an effect on blood pressure not unlike that of prescription BP drugs, or a reduction of ~5 mm Hg. Highly beneficial to health.

    To be polite, I think that the claims as regards the benefits of being cold and then warm may be slightly confused. Does it conflate changing temperatures with the benefits of taking exercise. Anyone who’s exercised can confirm that they may be comfortable for a short time at 15 degC, but after sitting still for hours, reality kicks in and one would rather that it was 20 degC or even 24 degC.

    Professor Fanger in Denmark did tests ad nauseam 40 years ago showing that humans haven’t apparently adapted to northern Europe and still like temperatures that are more typical of Africa.

    I adapt to this house being 24 degC internally in high summer, then I gradually become less comfortable as it cools down in September and October and at some point one needs heating.

  14. I have been a huge sauna / steam room fan since my late 20’s. Religiously going in 3 – 5x a week for +/- 30mins. I always follow up the heat treatment with a shower that is as cold as I can get the water. I’ve always found the sauna to be incredibly rejuvenating, especially after an evening of indulgence (those particular sauna sessions are called my ‘oil change’).

    My wife and I were having a great time attempting to conceive, but it began to feel like something was amiss. I began reading into male fertility and came across some information on how laptops were found to be bad for sperm count and that the prime suspect was the heat generated by the machine. Wait, heat is bad for the boys? hmmm 2 – 2 = 0 right? Anyway, I started soaking a face cloth in cold water and wrapping em up for the sauna session (I’m no quitter), sometimes having to re-soak the towel depending on the duration of the session, I did this for at least 6 months.

    Fast forward 6 years and our little girl is a healthy mix of astronaut and rock star! And her little sister is quickly becoming a mountain climbing music composer of her own 🙂

  15. Really hard to take cold showers in Las Vegas because the water comes from tap very warm and my pool is hot. Ugh….

  16. Thinking about picking up a sauna regiment, no A/C here in SE PA in summer except on extremely humid nights in the bedroom for good sleep (4 nights this year) and leave the heat on 54 at night during the winter will occasionally bring it up to 60-64 while relaxing (or an hour before wake up) if it is excessively cold out, but love both ends of the spectrum. Play/coach baseball 6-7 nights a week during summer and walk every morning to the train (15min) same in winter along with getting out for runs or a workout in my unheated attic. Always thought ‘Well I already paid for that sweatshirt might as well don it’.

  17. Mark, I’d love to hear your thoughts on the effects of cold exposure on sperm count/quality. It would be good to be able to do at least that while trying to conceive. Thank you