Trying to purchase a sauna these days is equivalent to purchasing snake oil. Have you got an ailment…check us out we’ve got the cure! The marketing behind saunas has appeared to take prevalence over accurate information and it has become a buyer beware market. In this article we address scientifically, and with references where possible, exactly what infrared is and what the different types of saunas are so you can get the maximum benefit for your circumstances.
Let’s first explain what infrared is. “The spectrum of solar radiation reaching the Earth ranges from 290 to more than 1,000,000 nm and is divided as follows: 6.8% UV, 38.9% visible, and 54.3% near infrared radiation (NIR) .
What we are interested in is a small bit of the visible and the majority of the infrared, and what this is saying is that of the solar radiation to reach the earth at sea level a full 54.3% is infrared and only 38.9% is what we see as visible light. There is a lot going on around us that we can’t see, and this light has different functions within the body that can be tapped into with the various types of saunas. First, we’ll look at visible, then near and then finally far infrared which is what provides the heat of a sauna.
Visible light is, on the surface, easy to understand. You see it. There is a little bit more to the picture than what you just “see” though. What is becoming better understood over the last 40 years is that light has physiological effects on the body. Effects that are required for optimal health, and one, but not the only, of these effects is called photobiomodulation or occasionally LLLT. Keep this word in mind as we will come back to this when we discuss near infrared. For now, simply understand that red light, with the right irradiance (power density) and dose is therapeutic and highly desirable in a sauna when you get the exposure factors correct.
NEAR INFRARED LIGHT
In order to understand near infrared (and red) light and photobiomodulation, it’s important to understand what is referred to as the mitochondrial stimulation band. This is a narrow band of wavelengths that can penetrate deep into the body, get absorbed by chromophores in the mitochondria and then exert a positive effect on the health, vitality and energy of the cell. The key here is that for any type of light to have a physiological effect it needs to have a receptor. This is an important consideration involving the optical properties of tissues.
Here is the technical information explaining this window in the human body which you can skip if all you want to know is that the range is ideal between 600-1150nm (red and near infrared) but can stretch out to about 1400nm.
The second important consideration involves the optical properties of tissue. Both the absorption and scattering of light in tissue are wavelength dependent (both much higher in the blue region of the spectrum than the red) and the principle tissue chromophores (hemoglobin and melanin) have high absorption bands at wavelengths shorter than 600-nm. Water begins to absorb significantly at wavelengths greater than 1150-nm. For these reasons there is a so-called “optical window” in tissue covering the red and near-infrared wavelengths, where the effective tissue penetration of light is maximized (Figure 2).” 
Let’s simplify. When you look at figure 2 notice that to the left and the right of the optical window there is a very HIGH absorbance of light. Nothing really getting deep into the body and the mitochondrial as all the light is absorbed by blood, melanin and water. However, when you have light between the red 600nm to the 1000nm or possibly as high as 1150nm in the near infrared range of light, there is very little absorbance meaning the light can penetrate and be absorbed by the mitochondrial light receptor enzyme called cytochrome-c oxidase where it has it’s positive effects on the body.
In short light between 600nm and 1150 ALL have a positive photobiomodulation effect.
Now the bit that most companies get very wrong.
The claim many companies make is that the only wavelengths that are going to work is 660nm and 850nm. Again, this is either lack of understanding the science, or more likely, manipulating it to suit a purpose. I mention the manipulation as both lasers and LED lights are essentially monochromatic and tuned to SINGLE frequencies of light. This means they have to pick ONE wavelength so it’s to their benefit if they claim that it’s the best or only way of getting photobiomodulation.
This is where language comes into play along with the marketing manipulation so let’s get clear on what the science has to say on the matter of what wavelengths work for photobiomodulation. Have a look at this diagram.
Notice the peaks of absorption! “A recent paper from Karu’s group gave the following wavelength ranges for four peaks in the LLLT action spectrum: 1) 613.5 - 623.5 nm, 2) 667.5 - 683.7 nm, 3) 750.7 - 772.3 nm, 4) 812.5 -846.0 nm.”
None of these falls in the 660nm or 850nm wavelengths claimed to be the best. Now let’s be clear and transparent. All the wavelengths will work as they are all in the mitochondrial stimulation band. It’s just that some may work better than others. Again in full transparency the research is continuing into what wavelengths will be best and it very well may turn out to be exactly 660nm and 850nm, but the point is that the full spectrum works and this full spectrum application may be how nature has intended it to be applied.
Now, lets talk saunas for bit.
The key to understanding an infrared sauna is that the heat is generated by mid and far infrared, NOT near infrared. Near infrared is photobiomodulation therapy and has very little to do with the heat that you need to get a sauna effect. Keep the two separate in your mind!
A near infrared sauna is a misnomer and should not be called that at all. It would be more accurate to term it a full spectrum sauna but again this could be misleading depending on how the NIR is applied. More on this in a bit.
I am 100% confident to say that far infrared is the workhorse of any sauna. It is what provides the heat and in turn detoxification and many other health benefits of a sauna. It is probably fair to say that it is virtually equivalent to typical Finnish saunas and any benefit found in those should be conveyed to FIR saunas.
Mid infrared I’m not convinced is all that important other than contributing a bit more heat.
In short FIR saunas are good. The only caveat is to be aware of EMF emissions and purchase wisely.
FULL SPECTRUM SAUNAS
Ahhh, the complicated and potentially misleading stuff!
A definition is in order first. A true full spectrum sauna is composed of all the wavelengths from red light (600nm) all the way through near infrared, then into mid and finally into far infrared. All of them.
Where liberties can be taken is when you add LED lights to a FIR sauna. For example, if you add an LED array of red lights (660nm) and NIR lights (850nm) can you consider this full spectrum?
The company that did this might, as technically you have some visible, some near and all the FIR you would expect. The purist would look at this and say what about all the other wavelengths you have left out? How can this be “full” spectrum? Who is right and who is wrong?
In my opinion this is probably the wrong question.
The right question is, if you are going to add red and NIR light (photobiomodulation) to a sauna is it effective?
This comes down to calculating the dose. This in turn comes down to the strength of the light, the distance you are away from it and the time you spend in front of it. Let’s explore but keep it simple.
Strength is determined by irradiance level and is measured in mW/cm2. As you move away from the light the strength decreases. In our example let’s assume you are sitting 60cm away from your light source. Example A will be in front of a LED panel (that we distribute) and Example B will be in front of an incandescent lamp (TheraBulb)
Now keep in mind that in example A the irradiance level of the LED’s is quite strong AND there is no blockage of the lights via the structure of the walls so at a distance you still get a healthy irradiance. In many of the “full spectrum” saunas out there you don’t get this. The critical factor is not that you have LED lights it’s the confirmation of what the irradiance levels are, and you need to ensure that the LED light is unimpeded.
Let’s get back to the dose. A healthy PBM dose will be between 3-60J/cm2 depending on if you are treating superficial vs deep tissues. Looks like both work.
So what’s the biggest difference?
In Example B we used TheraBulb incandescent lamps and these are truly full spectrum. LED’s are not technically full spectrum and over time this may prove to be a very important difference in how we get our PBM. The lamps mimic the sun and how nature intended things.
Often the lamps are discredited but when you look at the independent data this becomes clearly a marketing attempt to promote FIR saunas over NIR.
Have a look for yourself.
When you add up the percentage of output from the lamps in the mitochondrial stimulation band (600 to 1000) you can clearly see that a full 37% is in the therapeutic range. The vast majority of the rest of the output is mid and far infrared which is what provides you the heat for the sauna. Clearly you can get “two in one” therapy. The same independent testing showed the irradiance level at 60cm is 6.56mW/cm2. The science is clear. The marketing can make it fuzzy.
Occasionally you hear the argument that all of the PBM research has used either lasers or LED sources of Red and NIR light emitting single frequencies of these wavelengths so the lamps don’t work. This is simply not true, and some research does exist using full spectrum light. Regardless, we can’t become so reductionist to lose sight of the fact that the sun and its full spectrum is how we are designed to get our PBM.
Now one for the other side. If you need just the benefits of PBM then a full spectrum sauna with LED’s is perhaps the better option as you can move closer to get a higher dose. You can’t really move closer to the heat lamps to get an increased dose.
Saunas are pretty straight forward but the addition of photobiomodulation has complicated things. This has led to very murky levels of understanding and a whole lot of “creative” marketing.
If you are in the market for a sauna consider the following.
There are several ways to do this and all can be effective, but you need to understand the pros and cons of them.
All can work. As written above you need to consider EMF’s, cost, true full spectrum vs partial, irradiance, and if you need separation of the photobiomodulation from the heat source. Once you have done this you can make an informed choice.
Happy sauna hunting.
For more information contact Dr Todd Lizon B.P.H.E., D.C. at