With the rise of podcasting and influencers claiming to be wellness and longevity gurus, there is a lot of noise about “optimizing” our bodies. Anecdotal evidence and emerging empirical research have sought to address some of these questions, with a particular focus on hot and cold therapy as it relates to heart health, inflammation, and longevity.
Are ice baths and saunas just trends, or do they hold legitimate medical value?
Heat Therapy: The Sauna Effect
We need look no further than northern Sweden, a country where saunas are ubiquitous, to find data. Observational studies have linked frequent sauna use to a reduced risk of cardiovascular disease, higher quality sleep, improved mental status, and all-around better health.1 But why?
When you sit in a sauna (specifically a dry sauna at temperatures around 175°F to 195°F), your body undergoes physiological changes similar to moderate-intensity exercise. Your heart rate increases, and your blood vessels dilate (expand) to help cool your body. This process, known as vasodilation, improves endothelial function – the health of the inner lining of your blood vessels. Regular sauna use has been shown to lower blood pressure and improve arterial stiffness, both of which are critical factors in long-term heart health.
Furthermore, heat stress activates the production of “heat shock proteins,” which help repair damaged proteins and reduce oxidative stress. What does this mean for your health? A lot!
When your body experiences heat stress (like during intense exercise and sauna exposure), it increases production of heat shock proteins (HSPs). HSPs help refold damaged proteins that have been misfolded by heat. In plain terms, this keeps cells from breaking down during stress.
But they have more than one function.2 HSPs prevent protein clumping (aggregation) inside of cells and assist in removing severely damaged proteins. When proteins clump together, they can interfere with normal cell function and are linked to aging and diseases like neurodegeneration. A familiar disease we see this in is Alzheimer’s, where abnormal protein buildup is a hallmark. If damaged proteins aren’t removed, they accumulate like cellular garbage, impair energy production, increase inflammation, and accelerate cellular aging.
HSPs also support cellular survival pathways – they activate internal systems that help cells adapt to stress instead of dying, which improves resilience and makes cells better at tolerating future stress.
The most familiar function of HSPs is that they indirectly reduce oxidative stress by stabilizing mitochondria and improving antioxidant defense systems. Heat shock proteins don’t directly “neutralize” free radicals the way antioxidants like vitamin C do, and instead, they protect the cellular machinery that would otherwise be damaged by oxidative stress.
So, is a sauna or heat therapy a good idea? In general, yes, it seems like a healthy option for most people. However, if you have blood pressure issues or pre-existing heart conditions, talk to your doctor prior to indulging. The stress that sauna can place on the system to accelerate health benefits can also do the opposite in some health-challenged populations.
Be sure to follow proper protocols for using a sauna. Your sessions should be limited to approximately 20 minutes, and it is recommended to drink plenty of water both before and after a session to replace what is sweated out and reduce heat exhaustion. Also, certain medications like transdermal patches can have altered absorption rates when exposed to heat, and alcohol consumption can impair the ability to sweat. If you feel faint or dizzy while in a sauna, be sure to exit safely and consult a physician.
Cold Therapy: The Plunge
On the other end of the spectrum is cold therapy, or cold plunging. This typically involves immersing the body in water below 59°F. The shock of the cold causes immediate vasoconstriction – the narrowing of blood vessels. This forces blood to the core to protect vital organs. When you get out, the blood vessels dilate, flushing fresh, oxygenated blood back to the tissues.
Cold therapy is widely praised for its ability to reduce inflammation. For patients with osteoarthritis or those recovering from orthopedic surgeries (once cleared by a surgeon), cold therapy can significantly reduce joint pain and swelling. Additionally, the cold shock triggers a massive release of norepinephrine and dopamine, neurotransmitters that improve mood, focus, and metabolic rate.3
Some studies even suggest that shivering can convert white fat (energy storage) into brown fat (metabolically active fat), thereby aiding calorie burning. In one study, researchers wanted to see if being cold triggers the release of a hormone called irisin in humans.4 Irisin is released by muscles and has been linked to some of the benefits of exercise. They also looked at another hormone called FGF21, which is involved in heat production. Here’s what they found:
- When people were exposed to cold, levels of irisin and FGF21 increased in the blood.
- The more a person shivered, the more irisin they produced.
- The amount of irisin released from shivering was about the same as what’s released during exercise.
They also found that fat cells were triggered, specifically brown fat, into being more metabolically active, burning more energy and producing more heat. In other words, the cold makes us shiver, that moves the muscles, irisin increases, and fat burns to heat the body. While this is biologically interesting and could have potential for treating weight gain, the calorie burn from cold exposure is modest unless the exposure is intense and sustained.
Which brings us to the next point: sustained exposure to cold water can be detrimental.
According to the National Center for Cold Water Safety, “Short of being hit by a bus or struck by lightning, cold shock is one of the biggest jolts that your body can experience.”5 And exposure to cold therapy causes conflicting autonomic inputs to the heart.
In healthy people, this push-pull system is tightly coordinated to keep the heart rate and blood pressure stable: the sympathetic nervous system (CNS) speeds the heart up, as in a “fight or flight” response, and the parasympathetic nervous system (PNS) slows the heart down, as in “rest and digest.” Both are always active, and the heart rate at any given moment results from the balance between the two.
Cold exposure, especially when it’s immediate and shocking, does something interesting: it can activate both systems.6 Now you have two opposing signals hitting the heart at once, telling it to speed up and slow down. That conflicting input can create heart rhythm instability in susceptible individuals, increase arrhythmia risk in people with underlying heart disease, or cause exaggerated heart rate swings. It can also be electrically destabilizing for some people. The net effect depends on timing, intensity, body area cooled, and the person’s health.
When it comes to heart health, many experts might suggest skipping out on the next polar bear plunge.
Contrast Therapy
Some biohackers advocate for “Contrast Therapy” – alternating between the hot sauna and the cold plunge. This creates a pumping action in the lymphatic and circulatory systems, potentially accelerating recovery and detoxification. However, this can be even more destabilizing to the body, and caution especially needs to be exercised in people with existing heart and cardiovascular conditions.
A Word of Caution
While the benefits are promising, these therapies are not for everyone.
- Heart Conditions: If you have unstable angina, uncontrolled high blood pressure, or severe heart failure, the extreme stress of heat or cold can be dangerous.
- Neuropathy: Patients with diabetes who have neuropathy (loss of sensation) should be careful, as they may not feel if the water is too hot or too cold, leading to burns or frostbite.
- Post-Surgery: Do not submerge incisions in water (hot or cold) until your surgeon has explicitly cleared you, usually 4 to 6 weeks post-op.
- Raynaud’s Phenomenon: These patients are likely to experience severe vasospasm with cold exposure, leading to pain and tissue injury.
- Pregnancy: Extreme heat (e.g., hot tubs, saunas) may not be recommended, especially in early pregnancy, due to risks associated with elevated core temperature.
- Severe Anemia or Chronic Fatigue Conditions: Extreme temperature stress can worsen dizziness, lightheadedness, or fainting.
This list is not exhaustive, and when in doubt, ask if it’s appropriate for your unique circumstances.
Ultimately, hot and cold therapies are potent tools for inflammation and cardiovascular conditioning, but they should be viewed as supplements to, not replacements for, standard medical care, diet, and exercise. Always talk to your physician before beginning any new exercise or physical conditioning routine.
Dr. Tordini is a part of Florida Medical Clinic Orlando Health
- Engström, Å., Hägglund, H., Lee, E., Wennberg, M., Söderberg, S., & Andersson, M. (2024). Sauna bathing in northern Sweden: results from the MONICA study 2022. International journal of circumpolar health, 83(1), 2419698. https://doi.org/10.1080/22423982.2024.2419698.
- Hu, C., Yang, J., Qi, Z., Wu, H., Wang, B., Zou, F., Mei, H., Liu, J., Wang, W., & Liu, Q. (2022). Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities. MedComm, 3(3), e161. https://doi.org/10.1002/mco2.161.
- Corliss, J. (2025, June 1). Cold plunges: Healthy or harmful for your heart? Harvard Health. https://www.health.harvard.edu/heart-health/cold-plunges-healthy-or-harmful-for-your-heart.
- Lee, P., Linderman, Joyce D., Smith, S., Brychta, Robert J., Wang, J., Idelson, C., Perron, Rachel M., Werner, Charlotte D., Phan, Giao Q., Kammula, Udai S., Kebebew, E., Pacak, K., Chen, Kong Y., & Celi, Francesco S. (2014). Irisin and FGF21 Are Cold-Induced Endocrine Activators of Brown Fat Function in Humans. Cell Metabolism, 19(2), 302–309. https://doi.org/10.1016/j.cmet.2013.12.017.
- National Center for Cold Water Safety. (2025). Why Cold Water is Dangerous. Cold Water Safety; National Center for Cold Water Safety. https://www.coldwatersafety.org/the-danger.
- Jdidi, H., Dugué, B., de Bisschop, C., Dupuy, O., & Douzi, W. (2024). The effects of cold exposure (cold water immersion, whole- and partial- body cryostimulation) on cardiovascular and cardiac autonomic control responses in healthy individuals: A systematic review, meta-analysis and meta-regression. Journal of Thermal Biology, 121. https://doi.org/10.1016/j.jtherbio.2024.103857.
