Infrared Saunas — What the Temperature Actually Does to You
Traditional saunas have decades of cardiovascular data. Infrared saunas are newer, cooler, and more comfortable. But do they produce the same benefits? The evidence is more nuanced than the marketing.
The Finnish Data That Shocked Cardiologists
In 2015, Jari Laukkanen and colleagues at the University of Eastern Finland published a study that made cardiologists pay attention to saunas for the first time. They followed 2,315 middle-aged Finnish men for 20 years and tracked how often they used a traditional sauna.
The results:
| Sauna Frequency | Cardiovascular Death Risk (vs. 1x/week) |
|---|---|
| 2-3x/week | 27% lower |
| 4-7x/week | 50% lower |
Men who used the sauna 4-7 times per week had half the risk of dying from cardiovascular disease compared to men who used it once a week. They also had a 40% lower risk of all-cause mortality.
This was an observational study (not an RCT), and these were traditional Finnish saunas — high heat (174-212°F / 80-100°C), low humidity. But the magnitude of the association was difficult to ignore.
Traditional vs. Infrared: The Key Differences
| Feature | Traditional Sauna | Infrared Sauna |
|---|---|---|
| Temperature | 150-212°F (65-100°C) | 120-150°F (49-65°C) |
| Heating method | Heated air (convection) | Infrared radiation (direct tissue heating) |
| Penetration | Heats skin surface; body heats via conduction | Infrared waves penetrate 1-2 inches into tissue |
| Sweat onset | 10-15 minutes | 15-20 minutes |
| Core body temp increase | 1.5-2.5°F | 1.0-1.5°F |
| Tolerance | Intense; many people can't stay long | More comfortable; longer sessions tolerable |
The critical question: does the lower temperature of infrared saunas produce the same physiological responses as traditional saunas?
The Mechanisms
Heat exposure triggers several well-characterized physiological responses:
Heat shock proteins (HSPs). When your body temperature rises, cells produce heat shock proteins — molecular chaperones that protect other proteins from unfolding and aggregating. HSPs have anti-inflammatory, neuroprotective, and cardioprotective effects. They're activated at core body temperature increases of about 1-2°C — achievable in both traditional and infrared saunas.
Cardiovascular conditioning. Sauna exposure increases heart rate to 100-150 bpm (comparable to moderate exercise), dilates blood vessels, and increases cardiac output. Regular exposure improves endothelial function (the health of blood vessel walls) and reduces arterial stiffness.
Growth hormone. A single sauna session can increase growth hormone secretion by 200-300%. However, the effect is acute and transient — it doesn't produce the sustained elevation needed for significant muscle growth.
Norepinephrine. Sauna exposure increases norepinephrine by 100-200%, contributing to the alertness and mood elevation that sauna users report.
Endorphins. Beta-endorphin levels rise during heat exposure, producing the post-sauna euphoria that Finnish people call löyly.
The Evidence for Infrared Specifically
While the Finnish epidemiological data covers traditional saunas, infrared saunas have their own (smaller) evidence base:
Congestive heart failure. A 2004 study by Kihara et al. found that far-infrared sauna therapy improved vascular endothelial function, reduced arrhythmias, and improved symptoms in patients with chronic heart failure. A 2009 follow-up showed improved long-term survival.
Chronic pain. A 2005 study of chronic pain patients found that 4 weeks of infrared sauna therapy significantly reduced pain scores and improved quality of life. Effects persisted at 2-year follow-up.
Recovery. A 2015 study in SpringerPlus found that far-infrared exposure after exercise enhanced neuromuscular recovery in athletes compared to passive recovery.
Depression and fatigue. A small 2005 Japanese study found that infrared sauna therapy improved appetite, relaxation, and reduced complaints of somatic pain and depression in mildly depressed patients.
Detoxification. Infrared sauna companies frequently claim their products "detoxify" the body. The evidence is limited: sweat contains trace amounts of heavy metals (arsenic, cadmium, lead, mercury), but the quantities excreted through sweating are tiny compared to renal and hepatic excretion. Sweating is not a significant detox pathway. This claim is largely marketing.
The Caveats
Most cardiovascular data comes from traditional saunas. The Finnish study — by far the largest and most influential — used traditional high-heat saunas. Extrapolating those results to infrared saunas is reasonable but not proven. The lower temperatures and different heating mechanism may produce different magnitudes of effect.
Core temperature matters. The physiological benefits of heat exposure are dose-dependent on core body temperature increase. If an infrared sauna session doesn't raise your core temperature enough (due to lower ambient heat or shorter duration), you may not get the same benefits.
Dehydration risk. Both sauna types cause significant fluid loss through sweating — 0.5-1.0 liters per 30-minute session. Inadequate hydration before, during, and after sauna use can cause lightheadedness, headaches, and in extreme cases, heat-related illness.
Not for everyone. People with uncontrolled blood pressure, recent cardiovascular events, pregnancy, or alcohol intoxication should avoid sauna use. Multiple medications (diuretics, beta-blockers, vasodilators) can alter heat tolerance.
The Honest Take
Heat therapy is one of the oldest health practices on earth — every culture has some version of it. The modern evidence base, particularly from Finland, suggests that regular heat exposure is associated with genuinely significant cardiovascular benefits.
Infrared saunas are a more accessible, more comfortable version of heat therapy. The evidence for infrared specifically is smaller than for traditional saunas, but the mechanistic rationale is sound: if the core physiological response is core body temperature elevation, and infrared saunas can achieve that, the benefits should transfer.
The practical takeaway: use whichever sauna you'll actually use consistently. A $200/month infrared sauna membership that you visit 3x/week is more valuable than a $50,000 traditional sauna in your basement that you use once a month. Consistency matters more than the heating technology.
Stay hydrated. Don't sauna drunk. And if you feel lightheaded, get out.
Sources: Laukkanen et al., "Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events," JAMA Internal Medicine, 2015. Kihara et al., "Repeated Thermal Therapy Improves Impaired Vascular Endothelial Function," Journal of the American College of Cardiology, 2002. Beever, "Far-Infrared Saunas for Treatment of Cardiovascular Risk Factors," Canadian Family Physician, 2009.