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:
https://academic.oup.com/humrep/article/28/4/877/653255

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.

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