Photobiomodulation therapy has important implications for health that many are still under-informed about. In this interview, photodynamic therapy researcher Michael Hamblin, Ph.D., who is an expert in this area, sets out to improve our understanding of this important field.

Hamblin is a researcher and associate professor of dermatology at Harvard Medical School. He's also a principal investigator at The Wellman Center for Photomedicine at Massachusetts General Hospital, and a member of the Harvard-MIT Division of Health Sciences and Technology.

Infrared therapy is one aspect of photobiomodulation, which covers light of all wavelengths โ€” visible light, and light from spectral regions including ultraviolet, blues through the green, red and into the near-, mid- and far-infrared wavelengths.

One of the most commonly used wavelengths of light is the near-infrared, which starts at about 750 nanometers (nm) and goes all the way into 1,200 nm.

Near-infrared in the lower range penetrates well into the body and has many beneficial biological effects. Wavelengths beyond 1200 nm have very limited ability to penetrate deeply into the body.

Another type of infrared radiation commonly used is far-infrared, which also has biological effects. That's the type of infrared you get from an infrared heat lamp or far-infrared sauna. More specifically, an infrared heat lamp will give off mostly far-infrared; about 10 percent of the energy is near-infrared.

Far-Infrared Light Affects Your Biology by Altering the Properties of Structured Water

The two principal biological chromophores (light-absorbing chemicals) in photobiomodulation are the mitochondrial enzyme called cytochrome c oxidase (COO) and simple water.

Far-infrared is absorbed by water, which is why it cannot penetrate as deeply as the lower near-infrared range. The higher near-infrared wavelengths are also absorbed by water.

Now, if light energy is absorbed by the water in your body, how does the light affect your biology? Hamblin explains:
"The answer is that this is a concept called nanostructured water ... [N]anostructured water is present on hydrophobic surfaces, like certain kinds of cell membranes.
It could be inside the cell in various organelles, in the plasma membrane, the mitochondrial membrane and the endoplasmic reticulum (ER) membrane.
Virtually all membranes in principle can have nanostructured water ... The idea is that a small amount of vibrational energy in the water molecules can perturb tertiary protein structures, which is particularly important โ€” things like ion channels [which] have a huge number of biological pathways.
There's no real bulk heating when you use far-infrared, the sort of levels that get into the tissue. It may heat up the skin a bit, but at depth it can have biological effects by altering protein structure, mediated by nanostructured water ..."
Biological Effects of Near-Infrared

The mechanism of action for far-infrared differs from the red and near-infrared, the latter of which primarily targets the COO in the mitochondria.

The accepted mechanism in the mitochondria involves dissociation of the inhibitory molecule called nitric oxide (NO) from COO, increasing electron transport and ATP synthesis. NO also has important signaling effects.
"It's not clear that all the NO comes from dissociation of COO. The reason for that is ion channels. Turns out that a lot of ... transient receptor potential ion channels will activate various kinds of nitric oxide synthase or nitrite reductase.
There are several recognized pathways to NO ... Interestingly, the kind of light that produces these other NO pathways tends to be out of the blue or green, quite a long wavelength near-infrared. That's what we found in our labs.
The red and short near-infrared produce NO probably by a different pathway from blue, green and long near-infrared. That's our present understanding," Hamblin says.
"That's to say these nitric oxide synthase and nitrite reductase have been shown to be activated by ion channels, by transient receptor potential cation channel (TRPA1)."
Near-Infrared Helps Fuel Your Body

You probably know that the food you eat is converted to generate ATP. But the mechanism of ATP production can also be stimulated in response to near-infrared exposure, which triggers the mitochondria to produce additional ATP. So, it could be said that your body is fueled by both food and sunlight.

More specifically, light allows your body to use food more efficiently. In other words, light helps the cells make the best use of whatever food they have, and improves the generation of energy. "For instance, light seems to combine very well with modest amounts of exercise," Hamblin says.

The ideal way to receive most of this exposure would be to simply go outside, exposing as much skin as possible. Unfortunately, there are many areas where this would be impractical in the winter. This is where therapeutic light devices can be helpful.

The optimal wavelength for stimulating COO lies in two regions, red at 630 to 660 nm and near-infrared at 810 to 830 nm. Multiple studies have also failed to detect a difference between red light (660 nm) and near-infrared (810, 830).

So, the mid-600s and all of the wavelengths in the low 800s appear to have the same biological impact.

What this means is that the red light at 630-660 nm will provide the same mitochondrial benefits as the near-infrared range of 810 to 830 nm. Curiously enough, 730 nm does virtually nothing. One theory is that the absorption spectrum of COO has two peaks: one in the mid-600s and one at around 800.

Ideal Power Density

It's important to realize that photobiomodulation is highly biphasic in dose, meaning the benefit can disappear by using too much light. There's a dose range in which it will give you benefit.

Below that there is no effect and if you go a lot above the optimum you can actually cause harm. One factor to take into consideration is the power density, measured in milliwatts per square centimeter. There's a 10- and 20-fold positive window.

This means you could give 2 milliwatts per square centimeter or 30 milliwatts per square centimeter, and both would be effective. However, if you went to several hundred milliwatts it could be harmful. As a general rule, an ideal power density is around 10 milliwatts per square centimeter. Most photobiomodulation devices use between 10 and 20 milliwatts per square centimeter.

Get the Right Dose

The second factor is the dose, which is typically calculated in joules per square centimeter. Hamblin explains:
"When you have 10 milliwatts per square centimeter, that is 1 joule every 100 seconds, which is 1- and two-thirds minutes ... 10 joules is a reasonable dose. If you're treating things deeper in the body, you may want more than 10 joules per square centimeters. You may want 20 or 30; 100 is probably too much ...
What we don't really know is can you overdose the body on total joules or is it only when it's concentrated? That's what we don't know ... Ten minutes or half an hour does no harm at all ... Mostly, I tell people they can use these things for 10 or 20 minutes a day and it'll have major benefits and extremely unlikely to have any ill effects."
Frequency Modulation

The third factor is the frequency. Most of the devices referenced here are continuous wave, not pulsed, so there is no frequency. There's just a steady stream of photons coming out. You can modulate by pulsing the light, however. An ideal frequency is between 10 and 40 hertz. Anything over 100 hertz is unlikely to have a biological effect, or may even have a negative biological effect.
"By and large ... pulsing is better than continuous wave, and there is quite a bit of evidence [for this] ... maybe not a huge amount better, but definitely better. The optimum frequency is somewhere between 10 [and] 40 hertz. There was a study from Massachusetts Institute of Technology that got a lot of publicity when they used 40-hertz light flashing into the eyes to treat Alzheimer's in mice ...
They said 40 hertz [gamma frequency] was like a magic frequency. We did a study that found 10 hertz was better than continuous wave and better than 100 hertz. If pulsing is better, it's likely to be in that range and I completely agree that cells cannot respond to kilohertz. It's just way too fast for the cells," Hamblin says.
Sunbathing Versus Heliotherapy

Heliotherapy clinics were all the rage in Europe some 100 years ago. Patients would visit clinics in the Alps where they'd bask in the sun to treat a wide variety of chronic health conditions. Oscar Bernhardt, an early pioneer in this field, stressed the importance of sun exposure in mountainous areas.
"He said if you just go and lie in the sun on the beach, all you're getting is a sunbath. But if you go up in the mountains, you're actually getting a medical therapy," Hamblin says.
But why is sunlight so much better up in the mountains? Hamblin believes it has to do with the fact that, at high altitudes, there's much less atmosphere, and the lower oxygen level makes your mitochondria work at a different rate. The oxidative phosphorylation is more skewed toward glycolysis because the oxygen availability is lower.
"That's my pet theory," he says. "But people used to get complete chronic wounds healed by going to these heliotherapy clinics, just the same as you would do at sea level with our near-infrared LED array ... Provided you take precautions against getting too much ultraviolet, I think sunlight's fine. But we have busy lives and since you can get a therapeutic dose of near-infrared from an LED array for maybe 10 minutes a day, I think that's probably the way to go.
Another interesting thing [is] that throughout human history, people have liked to sit around fires ... [E]very evening people would sit around a fire and expose themselves to infrared, a lot of it far-infrared. That's [what] you get from glowing embers. It's only in the last 30 years that people have stopped sitting around fires regularly ... You could say Western civilization is suffering from a deficit of far-infrared light."
What Can Photobiomodulation Treat?

Most of the original research on photobiomodulation was done with lasers, but now they've started using light emitting diodes (LEDs), which are more cost-effective and don't have any safety concerns. LEDs also seem to be a more effective and efficient way to administer the therapy.

A recent trend is flexible, wearable LED arrays that you can wrap around your joints or put on your head or back โ€” typically to treat pain or degenerative conditions. They even have organic LEDs (OLEDs), where the actual light emitting substance is flexible. Different wavelengths impart different benefits:

- Blue wavelengths seem to be particularly good for relieving pain. On the other hand, extended exposure can damage the retina. As noted by Hamblin:
"Blue light is also good in the morning. It's quite clear that exposing yourself to blue bright light in the morning balances a lot of brain circuits. It's anti-depressant. It kind of gives you more alertness. As with anything, dose is key. You can probably more easily overdose with blue light than probably any other wavelength. I think you have to be careful with blue light because you can probably overdo it.
- Red light is good for relieving inflammation and inflammatory conditions. Interestingly, the literature is rife with reports on improving macular degeneration (the most common cause of blindness in the U.S.) with exposure to red light at 660 nm.

- Near-infrared is good for regeneration of deeper structures such as tendons, bones and cartilage; orthopedic and musculoskeletal problems. Red or near-infrared light at night also produces melatonin and helps you sleep. Near-infrared may also be useful for kidney problems. Anecdotal evidence suggests it could be a powerful therapy for kidney failure.
"Kidney failure is the third leading cause of death. These are old folks who are dying from kidney failure. You can't really give them transplants because they're elderly. You put a near-infrared LED array where their kidneys are and it seems to work like a dream. [But] it's hardly been studied at all," Hamblin says.
Folks, this is a GOLDEN pearl from this interview. Who would have ever thought that shining a light over your kidneys could radically improve kidney disease? It's certainly something that needs to be seriously considered by those with kidney impairment, as there is virtually no down side. Additionally, I have reviewed studies showing shining the light over your thyroid gland can be useful for autoimmune thyroiditis.

Near-Infrared Also Benefits Eyes, Diabetes and Athletic Performance

Metabolic syndrome and diabetes are two other conditions that could benefit from near-infrared light exposure. According to Hamblin, most people will place the light on the belly, as it is anti-inflammatory and can have a beneficial effect on fat deposits.

Near-infrared (810 to 830 nm) is also good for your eyes, so there's little risk in facing the light. Red light at 630 nm can dazzle you and take a while to recover from, but it's not actually harmful to your eyes. The startup company LumiThera is presently suggesting treating age-related macular degeneration with a photobiomodulation device that shines red and near-infrared light into your eyes.
"There are some clinical trials, but I don't know whether they're published yet. The odds are that it's highly effective and will eventually get Food and Drug Administration approval and they will be able to market this device to ophthalmologists. That's his business plan. It's a clinical device for ophthalmologists ...
In the future, we envision devices ... will be clinically used in hospitals and [by] ophthalmologists, even psychiatrists and all medical professionals. Then there would be a whole army of other devices that people have at home. I can see the day when every household will have one or two light therapy devices," Hamblin says.
"In Rio de Janeiro, in the Olympics, there were a lot of light therapy devices ... Athletes get huge benefits from putting red near-infrared light on their muscles. A lot of them use LED arrays. Some use whole body light beds. It's a huge big deal ... There's basically two ways athletes use [these devices]. One is preconditioning before your sports event ... the time to exhaustion is extended with light therapy ... and then there's after, which helps recovery and delayed onset muscle soreness ..."
Light Therapy May Boost Cognitive Function

Another fascinating area of discovery is the use of light to improve brain function. I recently interviewed Dr. Lew Lim about infrared light therapy for Alzheimer's disease. I will be publishing that interview shortly, so be sure to keep an eye out for it. It's fascinating stuff. Photons can be absorbed by the blood flowing in the skin, and it's known that light is very good at activating stem cells in bone marrow.
"A few folks with small trials for Alzheimer's get results so good that nobody can believe them," he says. "These are old folks who cannot say a coherent sentence, and in weeks or months suddenly start talking with their relatives.
People who have to be fed suddenly start using a knife and fork. I mean a lot of people just can't believe it ... In my opinion, the effects are so surprisingly good that this has to spread. People have to do big trials and I would expect in five or 10 years that photobiomodulation for Alzheimer's has to be pretty much out there."
Lim has invented a photobiomodulation device for neurological health and the treatment of dementia, but if you're on a tight budget, you could use a near-infrared (850 nm) security light from Amazon. I position it over my head for brain health. It can also be used on areas of pain, such as your back or knees. We have purchased an advanced spectroradiometer device to measure the precise amount of light this device emits so recommendations of distance from the body and time to use can be made.

You'll feel virtually no heat at all from these floodlights. This is as it should be because it's not the heat that creates the benefit, it's the wavelength. If you have a far-infrared sauna, you could further boost its benefits by adding an 850 nm near-infrared floodlight to it.

Photobiomodulation โ€” Medicine of the Future, Today

Photobiomodulation has been around for centuries but it's only in the last 50 years that its mechanisms have become (at least partly) understood. Unfortunately, as the pharmacological paradigm grew, so did the emphasis on expensive and dangerous medications. As a result, many simple yet profoundly effective and inexpensive strategies fell by the wayside. Take psychiatric drugs for example. They have virtually no positive benefits, but a large number of very serious side effects.

For brain health and Alzheimer's, "just putting a simple near-infrared light on your head works better than these drugs," Hamblin says. I sincerely hope that interest in these kinds of modalities will grow, and that scientists and medical professionals will give it more attention. As a layperson, you could also follow the parameters given to safely and successfully integrate this kind of light therapy into your life at a relatively low cost.