Saunas have become trendy in recent years as a tool for workout recovery and improving overall wellness. However, saunas (and heat therapy more generally) have been around for thousands of years, with important spiritual, medical, and social purposes across many cultures. Researchers have found that sauna, hot tub, and steam room sessions can be useful tools for decreasing glucose levels and improving insulin sensitivity.
What is sauna?
The term “sauna” is a Finnish term that means bathhouse . In Finland, where sauna is a national tradition, saunas are seen as a necessity rather than a luxury . To this day, they’re still an integral part of Finnish culture — there are 3 million saunas in Finland serving 5 million people .
Sauna structures in Finland have evolved over time. Traditionally, they consisted of stones that were heated in a fire and doused in water to create steam and heat . Now, they can be heated with hot stones, wood stoves, hot embers, or electricity. The savusauna (i.e., smoke sauna), which is located inside an unventilated space, is considered the most effective in Finland . Smoke is released into the room after the flames of a fire burn out and people enjoy the emerging heat.
Although integral to Finnish culture, saunas (and heat therapy more broadly) have been around for much longer — and served as important political, spiritual, and social meeting places throughout history .
Now, the term sauna is used to describe any heating system to heat the body and create profuse sweating. It’s seen as a relaxation technique, sore-muscle soother, social activity, and beneficial practice for overall health and wellness.
Types of saunas
There are different types of saunas, each varying in temperature and structure .
- Traditional sauna: Heat is generated by an electrical or wood-burning stove that heats stones to produce an intensely hot environment. Temperatures are set around 160–194ºF (71–90ºC).
- Infrared sauna: Infrared lamps use electromagnetic radiation to create a warm environment. Temperatures are set around 100–150ºF (38–65.5ºC).
- Steam/Turkish bath: A generator filled with boiling water is used to heat the space and create a wet and humid environment. Temperatures are set around 90–120ºF (32– 49ºC).
- Dry sauna: Hot air is used to create a high-temperature, low-humidity environment. Temperatures are set around 150–195ºF (65.6–90.6ºC).
Regardless of the type of sauna you choose, the benefits of heat exposure are consistent. So, whether you’re an avid sauna user or just starting out, select whichever you enjoy best.
What are the benefits of sauna?
If you prefer the traditional sauna or you enjoy the dry sauna, the effects on the body are similar — heart rate increases and the blood vessels vasodilate (i.e., widen) . This increases circulation and blood flow which mimics a moderate to high-intensity exercise session.
Sauna has many potential health benefits, including metabolic health outcomes and overall well-being:
- Improved cardiovascular health [5, 6, 7, 8]
- Reduced inflammation (though more research is needed in this area) [9, 10]
- Improved cognitive function and mental health [10, 11, 12, 13]
- Improved endurance and muscle mass retention (in animal studies) [14, 15]
- Improved release of toxins through sweat [16, 17]
Repeated sauna therapy sessions have been shown to improve endothelial (i.e., inner lining of blood vessels) and cardiac function in patients with chronic heart failure . One study consisting of 25 men found that infrared-dry sauna therapy for 15 minutes daily for two weeks improved endothelial function in patients with coronary risk factors such as high cholesterol, hypertension, diabetes mellitus, and smoking .
But newer research suggests that there are other benefits in addition to cardiovascular function, including blood sugar regulation. In fact, heat therapy plays a role in decreasing glucose levels and improving insulin sensitivity .
How sauna affects glucose levels
During a sauna session, body temperature rises and goes into a state of hyperthermia (overheating). To maintain homeostasis (i.e., balance within the body’s systems), the hormonal and nervous systems work together to bring the body’s internal temperature back down by increasing the amount of heat loss via sweating .
As it turns out, hyperthermic conditions can promote muscle growth by improving insulin sensitivity and decreasing muscle protein breakdown. This is largely due to the role of heat shock proteins (HSPs) such as Nrf2, FOX03, Interleukin-6, and Interleukin-10, which are present in all of your cells . One of their key jobs is to repair damaged proteins — a vital task because damaged proteins can lead to a number of degenerative diseases .
The hyperthermic conditions of a sauna place a lot of stress on your cells, which triggers increased production of heat shock proteins within your cells, with studies indicating that levels of certain HSPs may increase by up to 49% .
Increased levels of heat shock proteins can help improve cellular repair, reduce muscle atrophy, and decrease inflammation, which is linked to insulin resistance, dysregulated glucose, and other metabolic disorders.
Research indicates that the heat shock protein HSP72 specifically may help regulate the pro-inflammatory protein c-Jun terminal kinase (JNK), which is linked to insulin resistance and diabetes .
Other studies suggest that sauna sessions can assist in water weight loss and increase insulin sensitivity while also helping to reduce blood glucose spikes. In one study, after seven 15-minute sauna sessions, fasting blood glucose levels significantly decreased among 80 subjects (40 male, 40 female), aged 30 - 50 years .
Similar findings were found in individuals with Type 2 diabetes using hot tubs for 30 minutes daily, six days per week for three weeks . Along with decreased blood sugar levels from an average of 10.1 mmol/L to 8.8 mmol/L, the participants reported improved sleep and an increased general sense of well-being.
Other things you should know before trying sauna
Sauna usage: when and how often
Regular users can take advantage of sauna sessions weekly. The recommended allotment of time in a single sauna session is 15 minutes for healthy adults. First-time users should start with a shorter session to adapt to the heat and slowly build up to the maximum time.
There is no "best" time of day to use a sauna. Using a traditional sauna in the morning may help you feel more energized and increase productivity, while using an infrared sauna at night may promote better sleep . There are advantages to using a sauna both before or after a workout. So whether you’re a morning or night user or before or after workout user, your body will still benefit from whichever routine works with your schedule and makes you feel the best.
Note: To practice proper sauna etiquette, it’s advised to take a quick shower before entering a public sauna.
More research is needed for some high-risk populations and the health impacts of sauna usage:
- Pregnant women: Sauna use during pregnancy may carry some health risks to the developing fetus . You should consult with your doctor before using a sauna.
- Children: Children have lower sweat rates than adults, and therefore have less efficient regulatory systems when it comes to temperature control . However, for children over the age of 6 years old, sauna sessions appear to be safe while under adult supervision.
- People who are sick or on medications: Those taking prescribed or over-the-counter medications should consult with their doctor before using a sauna. Also, people with a fever or inflammatory skin conditions should avoid sauna use . If you have uncontrolled blood pressure or heart disease, consult a physician before using a sauna.
Proper hydration is crucial to maintain the body’s fluid balance, and dehydration can lead to increased blood glucose levels. The average person loses approximately 0.5 kg of fluid as sweat during a single sauna session . This fluid loss can be accompanied by electrolyte loss as well.
To prevent dehydration and electrolyte loss, people should drink at least one glass of water prior to and after sauna sessions as well as consume electrolyte-rich foods after a session. Some examples of high-electrolyte foods include vegetables, avocado, fish, nuts, and seeds. Alcohol consumption before or during a sauna session can also cause severe dehydration and should be avoided.
Seeing a spike in a CGM reading
If you are using a continuous glucose monitor, or a CGM, to regulate your blood sugar levels, you may see erroneous high glucose readings during a sauna session. However, this is normal and not a cause for concern.
Put another way, this kind of blood sugar spike isn't bad — and in fact is needed for your body to adapt to certain exposures (i.e., a sauna session, high-intensity workout, etc.).
Although consistent sauna use has many benefits, it is only one component of a metabolically healthy lifestyle and it’s not a cure-all for poor habits in Veri’s Four Pillars (diet, exercise, sleep, and stress). That said, it’s an excellent tool for cardiovascular health and balancing glucose levels, and if you have access, it can be a great way to promote relaxation and improve your cognitive and metabolic function.
- Sauna has been around for thousands years across many cultures, though it's most commonly associated with Finnish culture.
- Research is always ongoing, but we know that sauna has many benefits for cardiovascular health, cognitive functioning, and blood sugar regulation.
- To gain the health benefits of sauna, try out one to three sessions per week each lasting 5 to 20 minutes. If you’re a beginner, start slow and work your way up to a longer session.
- To see how saunas impact your glucose levels, use a CGM like Veri where you get real-time personalized data to your lifestyle and habits. You may see a glucose spike, but this is normal and not a cause for concern.