Saunas and Male Fertility: Everything Guys Should Know
Recently there’s been a lot of talk online about the health benefits of saunas. Much of this is being driven by men’s health influencers, including those known as “vitalists”, men trying to hack their bodies in order to live forever. As with any “hot” trend, it’s important to separate facts from hype. And because male fertility is the main mission of Snowballs Underwear, it’s important for us to make clear the science-backed effects of saunas on sperm health.
So here’s your comprehensive guide to everything a man needs to know about saunas, including what they do to his swimmers.
The Basics of Modern Heat Therapies
Most of our reliable, clinically controlled research comes from Finland, where a long-standing sauna culture has enabled large prospective studies on heat exposure and health. 90% of Finnish adults use saunas weekly, and the practice has been associated with substantial reductions in disease and mortality. Long-term cohort data show that 4 or more sauna sessions per week are linked to a 40% lower all-cause mortality, which equals (and sometimes exceeds) data seen with many established lifestyle interventions such as regular exercise or Mediterranean-style diets.
Saunas induce cardiovascular responses similar to low-intensity aerobic exercise (zone 1-2), including increased heart rate and improved vascular function. So if you’re using a sauna, be sure to stay hydrated. And because you’ll sweat out a lot of salt, it’s recommended you hydrate not only with water, but with electrolytes.
Now let’s get to the specific benefits.
The Clinically Demonstrated Benefits of Saunas
All sorts of miraculous claims are being made about saunas. Here’s a concise list of what we know for certain. Saunas:
1. Improve blood flow & muscle recovery
Sauna heat causes vasodilation, increasing blood flow by up to 50–70%, which delivers more oxygen and nutrients to muscles. This improves post-exercise recovery and reduces stiffness (Brunt et al., J Physiol, 2016).
2. Boost metabolism & endurance (heat conditioning)
Raising core body temperature increases heart rate and energy expenditure, with metabolic rate staying elevated 30–60 minutes post-sauna. Heat acclimation studies show up to a 32% improvement in endurance performance after regular sauna use (Scoon et al., J Sci Med Sport, 2007).
3. Reduce inflammation via stress-hormone signaling
Short sauna sessions trigger controlled releases of adrenaline, noradrenaline, and cortisol, which temporarily suppress muscular and cellular inflammation and enhance recovery (Laukkanen et al., Prog Cardiovasc Dis, 2018).
4. Promote sweating, lower blood pressure & aid (some) detox
Sauna-induced sweating reduces plasma volume and sodium concentration, lowering blood pressure. Studies show measurable reductions in heavy metals like mercury through sweat, confirming sweating as a legitimate detox pathway for some substances (J Environ Public Health, 2012).
5. Improve mood via serotonin activation
Heat stimulates neurons in the dorsal raphe nucleus, increasing serotonin production. This is linked to improved mood, focus, stress resilience, and overall well-being, all benefits observed consistently in frequent sauna users (Laukkanen et al., JAMA Intern Med, 2015).
6. Reduce risk of dementia
In large Finnish cohorts, men who used a sauna 4–7 times per week had a 66% lower risk of dementia and a 65% lower risk of Alzheimer’s (Age and Ageing, 2016) compared with once-weekly users.
Brian Johnson, a longevity influencer who’s trying to live forever, began a sauna protocol, tracking markers to determine the real health benefits. His results were extraordinary and got a lot of press. We'll look at some of those in this article, as well as some fairly obvious lessons for male fertility.
How Hot Is Healthy?
The benefits of saunas – especially the reduced risk of dementia mentioned above – appear to depend more on frequency and moderate heat than on extreme temperatures. In the Finnish dementia/Alzheimer’s study, which tracked the same men over 20 years, sauna use 4–7 times weekly showed a 40% lower mortality from all causes (JAMA Internal Medicine, 2015), as well as the 65% lower risk of dementia/Alzheimer’s.
However – and this is important – a detailed analysis of sauna temperature in a separate large Finnish cohort showed a temperature-dependent pattern: the most favorable dementia risk reduction was seen at 80–99°C, while temperatures above 100°C (212°F) were linked to a higher risk of dementia compared with lower temperatures.
In short, more extreme heat has shown increased dementia risk, so aim to stay at or below 90°C (190°F).
When Brian Johnson overheated in the sauna, he started bringing ice packs into his sessions (hopefully he'll also look at the dementia research showing his brain will be better protected at slightly lower temperatures). He realized that frying his body would also fry his sperm. We'll get to the reasons for that below.
Do Saunas Actually Remove “Toxins”?
Johnson's big hope for his sperm protocol was that it would help remove "toxins", leading to greater longevity.
But is sweating really an effective way to get rid of anything more than trace amounts of toxins (an intentionally vague word that tends to elicit fear - nobody wants to be "toxic"!)?
Maybe, but the evidence for this is sparse, and often overstated, or intentionally vague.
Here’s what we know for certain:
1. Heavy metals are detected in sweat
Several toxic heavy metals have been measured in human sweat. In a systematic review of 24 studies, researchers found that arsenic, cadmium, lead, and mercury are present in sweat samples, often at concentrations that equal or exceed those in blood plasma or urine in exposed individuals. (PMC)
2. Other trace metals show excretion through sweat in small studies
Older clinical research has shown that nickel, cadmium, lead, copper, manganese, zinc, and iron can all be detected in sweat. Some (e.g., nickel and cadmium) were observed at levels higher than reported in urine under controlled collection conditions. (PubMed)
3. Heavy metal excretion varies depending on “active” or “passive” sweating
A controlled study directly comparing dynamic exercise and sauna conditions found that nickel, lead, copper, and arsenic concentrations in sweat were significantly higher during exercise-induced sweating than during passive heat (sauna), though mercury levels were similar across conditions. (PMC)
4. Other chemicals beyond metals may be detectable in sweat
Research on sweat composition suggests that persistent organic pollutants (e.g. BPA and certain phthalates) can also be present in sweat at measurable levels, sometimes when undetectable in blood or urine. These findings come from studies that measured a range of environmental toxicants in sweat, but they also note important methodological limitations with collection techniques. (PMC)
“Toxin” takeaways:
- Just because a substance appears in sweat doesn’t mean saunas reliably “detox” the body in a clinically meaningful way.
- Liver and kidneys remain the primary organs for eliminating most toxins and metabolic waste. The amount of toxins excreted via sweat is generally small relative to urinary/biliary excretion, and measured concentrations can be influenced by how sweat is collected and analyzed. (PMC)
In short, while saunas may help “detox,” sweat is not the body’s principal method for removing toxins. That doesn’t mean saunas don’t have other real benefits, however, as shown above.
Saunas, Semen, and Microplastics
Before we move on from toxins, here’s one more point. Johnson claimed that his sauna protocol reduced microplastics in his semen by about 85%, and a lot of online interest has centered on this. Could he have somehow sweat out all those microplastics in his semen?
Probably not. Recent studies have confirmed the presence of microplastics in human semen, but no clinical research that we’ve seen has tracked the effects of sauna use on microplastics. While sweat glands are designed to excrete water, electrolytes, and certain small chemical compounds, they are not known to eliminate solid microplastic particles. Some research does suggest that sweating may help reduce exposure to plastic-associated chemicals like BPA (incidentally, Snowballs ice packs are BPA-free), but that’s not the same as removing microplastics themselves.
All that said, while a lot of claims out there seem outlandish, the bottom line is that any reduction of toxins could bring fertility benefits. If you’re getting healthier, inside and out, you’re likely getting more fertile.
Dry Sauna vs. Infrared Sauna vs. Steam Room
Almost all the best evidence for the health benefits of saunas comes from studies of traditional Finnish dry saunas. These saunas operate at high temperatures (typically 80–100°C / 176–212°F) with low humidity, creating substantial thermal and cardiovascular stress. Large prospective cohort studies from Finland consistently associate this exposure with reduced cardiovascular disease, stroke, and mortality.
There's still very little data on any potential benefits of infrared saunas, which heat the body via radiant energy rather than heating the surrounding air, and typically operate at much lower ambient temperatures (45–65°C / 113–149°F). While infrared saunas are popular due to lower heat tolerance and reduced maintenance, they do not replicate the thermal load used in the Finnish sauna studies, and there is currently no comparable long-term outcome data demonstrating similar cardiovascular or mortality benefits.
Steam baths operate at lower temperatures but high humidity. While they can induce sweating, the high humidity limits evaporative cooling and generally results in lower core temperature elevation than dry saunas. As a result, steam rooms are also rarely cited in long-term health literature.
In short: the best-studied sauna benefits are clearly tied to high-temperature, low-humidity dry saunas. Infrared saunas and steam baths may feel beneficial and promote relaxation or sweating, but they cannot currently be assumed to deliver the same physiological or long-term health benefits.
Saunas and Male Fertility
Sperm production is highly temperature sensitive. Sperm develop best at 1-2°C / 3-5°F below core body temperature. That’s why the testicles are outside the body. In healthy men, heat damage is usually reversible. It takes about 3 months to form mature sperm, so after stopping heat exposure, count on at least 3 months of recovery before you’re no longer firing blanks.
Obviously, saunas expose the body to sustained high heat, which is practically guaranteed to harm sperm. Bryan Johnson, however, found that 3 weeks of his sauna protocol increased his fertility markers by 31%. In this clip, he asks whether his fertility improved because of the increased blood flow from a high heat sauna while icing his scrotum…or simply because he was icing his scrotum.
You don’t have to have a medical degree to see immediately that one of those two options is highly more probable than the other.
Let’s start here: one of the classic conditions causing male infertility is a varicocele, and they’re remarkably common. A varicocele in the scrotum is similar to varicose veins in the legs: branching veins that end up looking a bit like a frayed rope. This harms male fertility because the branching veins in the scrotum bring more blood. And blood brings more heat. Which, again, damages sperm. This is an undisputed fact that dozens and dozens of clinical studies since the 1960s have proven. Multiple peer-reviewed studies have also shown that regular sauna use temporarily reduces sperm concentration, motility, and morphology.
When we saw Johnson’s data, we were hoping he would record his fertility markers after a sustained period of using the sauna without an ice pack protecting the family jewels. Fortunately, that’s exactly what he did. You probably won’t be surprised by the results:
Why Men Wear Snowballs Underwear in the Sauna
Since 2012, Snowballs Underwear have been an effective and very popular way for men who are trying to conceive to boost their fertility. Since the personal experiments of Johnson and other men’s health influencers, however, we’ve seen a huge boost in sales to men who care about their fertility even if they’re only planning to have children at some point in the future.
Snowballs are the standard for this. There have been clinical studies done on Snowballs (Zumstein et al., Cent European J Urol., 2021, etc.). They’re made from breathable organic cotton rather than synthetic fabrics, which tend to trap heat and moisture, worsening scrotal overheating, especially in the sauna. Organic cotton allows better airflow and reduces moisture retention even in high heat environments.
Second, Snowballs don’t shed microplastic fibers. Synthetic underwear can release microplastics when heated or when exposed to sweat, putting the body in contact with plastic shedding just at the moment when pores are open.
Third, Snowballs provide light, ergonomic cooling support without compression (compression increases heat retention).
While no underwear cooling system can override high sauna temperatures, Snowballs minimize damage and help you avoid making your situation worse. Snowballs ice packs have also been tested at 90°C without showing any degradation.
Stay cool out there!
