In this episode, I’m back for a third installment of my conversation with Dr. Mark Cronshaw, one of the world’s foremost photobiomodulation (PBM) experts…what most people commonly refer to as red light therapy. He’s particularly one of the top experts when it comes to dosimetry (the details of how to properly “dose” light therapy).
Have you invested in red light therapy but feel confused by contradicting information?
You’re certainly not alone.
In this conversation, Dr. Cronshaw challenges conventional wisdom about photobiomodulation with some insights that surprised even me! I deeply appreciate his highly informed and logical, yet relaxed, approach to this complex topic.
WARNING: My conversations with Dr. Cronshaw are NOT a simple or practical how-to guide of “go buy this device and use it this way.” This podcast series intends to go deep into the scientific, technical, and theoretical nuances of PBM science. So it’s NOT for everyone. These podcasts are for people who want to nerd out on PBM science. So please don’t say I didn’t warn you! 🙂
Table of Contents
In this podcast, Dr. Cronshaw and I discuss:
- Why the concept of the “magic photon” might be oversimplified (and what Dr. Cronshaw proposes instead)
- The surprising truth about what matters more than melanin or hemoglobin absorption in light therapy
- How your body might have built-in “fiber optic cables” transmitting light to places sunlight never reaches
- The unexpected relationship between water content in tissues and light penetration
- The startling revelation about blue light’s potential benefits (when used correctly)
- How your myelin sheaths might secretly be transmitting photons throughout your body
- Why the “best wavelength” debate misses a fundamental understanding of photobiomodulation
- The controversial idea that multiple wavelengths might produce synergistic healing effects
- How the skin may function as a “neuroendocrine interface” that responds to light therapy
- The critical difference between using light for health maintenance versus therapeutic intervention
- Why penetration depth arguments aren’t telling the whole story about photobiomodulation
- How your entire body might be “light-sensitive” in ways science is just beginning to understand
- The real reason some wavelengths might be harmful (hint: it’s not about the color)
- Why Einstein’s principles about energy might be more relevant to PBM than specialized receptors
Listen or download on iTunes
Listen outside iTunes
Transcript
Ari: Dr. Cronshaw, thank you so much for joining me. [unintelligible 00:00:03] enjoying this conversation with you. It’s been very enlightening. We’ve had a lot of outside communication as well via email, and phone calls, and Zoom calls, and I’m learning a lot from you, and really greatly benefiting from this conversation. I’m fascinated [unintelligible 00:00:20] the knowledge that you have here, and I’m excited to continue this conversation with another podcast, another geeky photobiomodulation podcast that gets into the weeds in these key areas, and certain key areas of controversy.
The different wavelengths
With that in mind, let’s jump straight into [unintelligible 00:00:41] I think a good place to start would be wavelengths, because [unintelligible 00:00:45] you’ve hinted a few times in conversations we’ve had that you have some [unintelligible 00:00:52] different view, I think, than most people, and certainly a different view than the one that I’ve presented, and you’ve hinted that you may anger me a little bit by presenting this view that maybe ruptures my way of thinking about things. I would love to dig into that with you, and see how you think about wavelengths, and what you think maybe some of the big [unintelligible 00:01:14] are in that area.
Dr. Cronshaw: Absolutely. Well, the issues in regards to wavelengths are such that, you can really look at from the perspective of which wavelength should I use? That’s a very common problem. People say, “Hey, I hear I need to use a red wavelength for this,” or, “I hear a near-infrared wavelength is going to be best for this, and this is a longer wavelength than some of the other wavelengths, and they say this is better for these applications.”
This is one of the areas I got very interested in when I was studying for my thesis, when I was doing my doctoral work, and I really dug into this. To try and understand, well, both what is it that the energy is doing for different wavelengths, and is there a specific wavelength that you’ve got to use to produce the response you’re looking at? Then, I also looked at the differences between wavelengths in the red to near-infrared, and then I looked outside the box to, well, shorter wavelengths, like blue wavelengths, which are now being much talked about in the PBM community.
Is this PBM, or is this another effect? Historically, the view was always, it was a red to near-infrared wavelength, and then there are longer wavelengths too, in the mid-infrared to the far-infrared, which some people say, “Well, this is PBM too.” When you ask the question about wavelength, this is where you have to think really, I think, in essence, what is it? what is the essence of the wavelength?
The wavelength is referring to a packet of energy, right? It’s not a ping-pong ball of different dimensions. It’s not anything other than a conglomeration of energy. I mean, we refer to it as the photon. A photon is something which has got a magnetic field, an electric field, and then there’s the length of the cycle. According to the length of the cycle, this is what we refer to as the wavelength.
The shorter the wavelength, then the more energy that’s attached to that unit we refer to as the photon. Very short wavelengths got a real– Lot of punch, whereas some of the longer wavelengths, it’s more of a tickle than a punch. This can start to have an impact then on the tissues in regards to which wavelengths might use for different indications.
For example, dermatologists use blue and ultraviolet wavelengths, which are really short, but very powerful photons, as it were, to kill bacteria, which might be causing facial acne, as well as to help treat other dermatological conditions where they’re really wanting to apply a lot of energy there, as opposed to a small amounts of energy.
That higher energy is producing quite a different effect than if you’re choosing which is a longer wavelength, where you may just gently warm things up a little, and at least that’s the only thing you can feel. Then, you may be achieving different things too, because the properties associated with the wavelength will be such as how deep can that photon go into the tissues.
Now, if you’ve got something which is below the surface of the skin, and use something which is going to get very highly absorbed in the skin, well, that’s a rationale for choosing the one wavelength, as opposed to the other. When you’re thinking about PBM, first of all, you don’t want to use something which is too hot and too strong, something which is going to start to [unintelligible 00:05:00] tissues and coagulate proteins. Maybe some of these very short wavelengths like the ultraviolet ones that your dermatologists are using, these are not, perhaps, the best choices, particularly, because some of them can be mutagenic. They can trigger off cancer [unintelligible 00:05:15] in the skin.
Whereas if you’re thinking about delivering energy just to the surface of the skin, and you can use quite a number of wavelengths, but the red one is one which is very familiar in the PBM community, largely, because this is the one on which most of the research has been done. We know a lot about it. We know about its positive benefits in terms of stimulating the type of cell that produces collagen, fibroblasts.
We know that this can be something which is effective. Whereas if you start to think about longer wavelengths, and here, these are ones that you can’t see, because they’re just outside the visible spectrum of the human eye, but really, would be about 780 nanometers and longer, then these have got deep penetration. That’s a better wavelength to choose if you want to reach something which might be a centimeter or more deeper into the tissues, as opposed to something which will be much more superficially absorbed.
The criteria in terms of selecting wavelengths, in part, depends on the amount of energy associated with the individual photon, as well as what is it that you’re trying to achieve? Are you trying to do something which is superficial? Are you trying to do something which is deeper? Then, there’s all this stuff, in the sense that, people say to you, “No, you want to use this specific wavelength, a 1064, or a 1070 nanometer. This is the best wavelength. It goes the deepest,” and things like this. Do you know that’s not actually true?
Ari: Right, there’s a lot. Yes. Sorry, go ahead.
Dr. Cronshaw: There’s this– There’s a lot of ideas out there where people say, “Well, these are the wavelengths which are least absorbed in melanin, which is the pigment in your skin, and least absorbed in hemoglobin, blood, because tissues contain melanin and hemoglobin. If you want to get in deeper, then use these longer wavelengths, because these have got,” when they get, they produce these graphs, these absorption curves. PBM guys, they just love absorption curves. These very complicated looking graphs showing the differential, and they say, “Look, when you look at the–[crosstalk]
Ari: For people listening, if you want to look up what he’s referring to, which I recommend doing, you can do a Google image search for the optical window in photobiomodulation, and you’ll see these graphs that show the absorption curves of different compounds, melanin, water, hemoglobin. Is there another one? Those are the–
Dr. Cronshaw: Oh, yes. That’s a good point you see, because they didn’t talk about protein as well, and tissues contain lots of protein. Also, there is no weighting of the relative contents of the tissues. When I was looking at this in relation to the choice of wavelengths, I thought, “Yes, sure, I can see from this graph that melanin is quite poorly absorbed by these longer wavelengths, like the 1064, 1070 nanometer ones, whereas the red ones, they are more highly absorbed.”
Then, if you think, “Well, how much melanin is there in tissue?” Melanin, it’s that layer of pigment which is present just as a, more or less, one cell deep at the base of your skin, after which there’s not a lot of it in the deep tissues, if any. Whereas biological tissues comprise largely of water, that’s the single most predominant molecule present. You’ve got 55% to 60% water present in the tissues.
You look at the water absorption curve, and you think, “Oh, okay.” Well, the absorption curve for the 810 nanometer wavelength, which is a near-infrared one, but outside the visible spectrum, but shorter than these ones that have got some lower absorption of melanin, that is, if you look at that optical window concept, that goes really deep. You ask yourself, “Well, why?” That’s more highly absorbed in pigments. Yes.
Ari: Which wavelength was that?
Dr. Cronshaw: That’s the 810 nanometer. The answer is, because it’s got very poor absorption in water. As a result, it goes deeper into the tissues. Where the longer wavelengths, like the 980 nanometer and longer, these are, they’re not highly absorbed, no, but there’s significant absorption by water to the extent where this is providing a sufficient level of absorption, because of the volume of water that’s present to impede the delivery of that photon into the deeper layers of the tissue. The water is actually more important than the melanin, and the same with blood.
It’s very familiar in the literature. People say, “Oh, no, well, blood is a high absorber of some of these wavelengths.” Red and the immediate near-infrared, they’re very highly absorbed by hemoglobin. They show the oxyhemoglobin, which is the oxygenated blood, and the deoxygenated hemoglobin. There’s a subtle difference between the two in terms of the absorption.
They get really excited about the difference in terms of the absorption in that, whereas the amount of blood and tissues is really small. Tissues are only perfused maybe by 1% to 2%, unless it’s something like the thyroid and the brain. The amount of blood that’s present isn’t huge. Blood itself, well, it’s about 50% red blood cells. Those red blood cells contain maybe about 10% hemoglobin, which is the thing which is absorbing it.
That hemoglobin, the amount of free iron present is around about 0.5% to 1%. When you start to do the numbers, you realize that actually this– The significance of the absorption in terms of blood and hemoglobin is hugely overstated by comparison to the effects of the absorption by other elements in the tissue, which may include protein, or which is predominant in tissue, or water, which is very highly predominant in tissue.
Although the absorption curve may be lower, because there’s so much more of it, it’s much more important. [chuckles] This whole argument to do between the various manufacturers, which is what it boils down to is, manufacturers’ wars, and some conceptual issues to do with the relevance of the absorption curve is such that, it’s the wavelength which has got the deepest penetration to the tissues is around about 800 to 810 nanometers.
Whereas the shorter wavelengths, and the longer wavelengths up to 1070, they don’t have deeper penetration, even if it’s an absolute monster of a machine. Some of these 1064 nanometer ones, they’re what’s known as free running pulse lasers. It’s just the amount of energy they can pump out, is what you can describe as industrial. You’re talking about tens of thousands of watts, but maybe only for a couple of millionths of a second.
Ari: You’re talking about 1064 nanometer lasers?
Dr. Cronshaw: Yes. The amount of peak power there is vast. They’re saying, “Oh, this is really going to drill those photons deep into the tissues.” The on-the-bench studies showed, no, they don’t, because the direct measurements of those wavelengths, I can direct you to some nice studies that show that at about a centimeter deep, it makes absolutely zero difference peak power.
There’s lots of misconceptions where people have taken an idea and thought, “Yes, this is this is the answer.” You build up these hugely powerful, but very short duration, little pinpricks of energy, but they’re really steep spikes going deep into the tissue. No, they’re not. In every area of science, there’s always going to be an evolution and knowledge, and in respect to wavelength, partly, perhaps because of my participation, but also with other people, there’s been a reason where we’re starting to think, “Well, actually, the relative significance of one factor as opposed to another.”
If you then start thinking outside the box, which is in terms of the red to near-infrared, which is the traditional range that we think of using for PBM, there’s evidence of photobiomodulation as an activity present in shorter wavelengths, like the blue and the green and the yellow wavelengths. That same with the longer wavelengths outside of the normal near-infrared range in the mid-infrared, as well as in the far-infrared.
You start to scratch your head and think, “Well, what is it?” Obviously, it’s not a magic photon, which has got its name on it saying, “Hi, I’m Mr. PBM photon.” It doesn’t work quite that way. This is a transfer of energy, and it’s to do with the transfer of this electromagnetic energy into something which then the cell can use one way or another. This is the primary issue.
Then, you have to think, “Well, what is it actually doing inside the cell?” That’s a whole different question. If you say to me, “Is wavelength important?” Sure, it is, because from a pragmatic point of view, you want to choose a wavelength, where you’re not going to over-energize the cell, it’s going to reach the target that you’re reaching for. If you say to me, “Well, can it only be specific wavelengths?” Does it have to be the helium-neon 632.5 laser, as some people would claim, or you want to use a 660 nanometer, it’s much better than a 650 nanometer, or, “No, you want to use a 1064.” I’m going to say, “Rubbish, because the best photon is the one that you got.” [laughs] You can– All these things–
Ari: Okay, so– Sorry, go ahead.
Dr. Cronshaw: That’s fine. I was just going to say, you could apply many different devices. Then, you have to understand the aspects in relation to the delivery of those photons, what’s actually happening to them inside the tissues, the impact they’re having on the tissues, as well as the depth that they will be received. This is a whole different argument, because you’re not just looking then at the absorption, which is the ability of the photon to get into the deeper layers, but there’s a phenomenon called scattering, where the photon enters, and a little bit like in a pinball game, it ricochets off, and that can then interfere depending on how much of that scattering that this pinball effect you get, how deep it goes.
Then, there’s the idea of– Well, along the way, you can get a little bit of absorption, and a little bit of continuation of the photon. Along the way, then things start to– It casts off some energy. What’s happening to that energy? You’re getting some heat. Then, you then have to think, “Well, are there photothermal aspects to this? Is this a hazard, if things start to get warm? Because I hear, that if you heat things up, then this could be a problem.” When you ask a simple question such as, what do I think about wavelength? Well, we could be here for hours, Ari.
Ari: I get that sense. Let me push back on this a little bit. You kind of– Again, don’t let me misrepresent anything you’re saying, because I’m going to simplify things here, but correct me if you disagree with this. You’re making a case for this idea that a photon is a photon, and, yes, there’s differences in how they penetrate into the tissues, and what they’re going to get absorbed by. For the most part, it’s electromagnetic energy. It’s energy being delivered to the tissues. Is that reasonable?
How PBM works on a biochemical level
Dr. Cronshaw: I think that’s a good start. There’s a layer of finesse I’d add to that, which is that, some photons do have what we call a resonance with biological molecules. Now, what is resonance? Well—
Ari: Can we stay away from that for just a moment? I want to get to that later, but I just want to push back on this topic that you were speaking about before. Is that okay? Okay. From that frame, and you were brushing off the idea that there’s a magic photon, as you described it, that it’s this unique thing, it’s more– You’re creating the idea that, more broadly, we can think of this stuff as packet of electromagnetic energy.
There is a case for magic photons. Not magic photons, but there is a case for this high degree of wavelength specificity. I know we brushed [unintelligible 00:18:58] VB wavelengths right around 300 nanometers. The activation of the circadian rhythm, and via the eye pathway, activating certain regions of the circadian clock in the suprachiasmatic nucleus of the brain depends upon, I think it’s 480 nanometer blue light, roughly in that range is where it’s active the most.
It’s not stimulated by wavelengths well outside of that by red, or let’s say, far-infrared, or things like that. Melanin in the skin is UVA predominantly, and UVB to some extent as well, specifically, in the 300, 400-ish range. There is this specificity to very specific narrow bands of wavelengths that have unique effects. You can’t get melanin synthesis or the conversion [unintelligible 00:19:56] the vitamin, pre-[unintelligible 00:20:00] with red light, or far-infrared or something like that?
Dr. Cronshaw: In order to produce a biochemical effect, you have to have sufficient energy, right? This is basic, a 101 biochemistry. When it comes to turning dehydrocholesterol in your skin into provitamin D, which is the precursor for the formation of vitamin D, you need to have a pretty energetic photon, which is a UVB one, all right? If you haven’t got the energy, you don’t get that effect. Sure, but then you’re looking at a very specific biochemical pathway, all right? Associated with the manufacture of vitamin D from cholesterol, whereas there are more broad aspects to PBM where you’re looking at some–
Ari: Hold on, you cut out there briefly. I don’t know if it was just on my end.
Dr. Cronshaw: Okay, yes. Well, I was– [crosstalk]
Ari: You said– The last thing I heard was you’re looking at a very specific–
Dr. Cronshaw: Yes, that’s right. You’re looking at a very specific biochemical pathway, all right? Now, this has been something which has been latched onto by the PBM communities, indicating that all PBM activities are specific biochemical pathways, where you’re triggering off unique biochemical events by the combination of a specific wavelength of photon produced in effect.
Professor Tiina Karu, who’s a Russian professor, spent a lot of time in her career looking at red wavelengths, as well as 780 nanometer wavelengths, looking at the specific absorption of that by one particular unit of the component of the mitochondria, which is called the electron transport chain, where there’s a specific enzyme called cytochrome C oxidase. This was the route which explained everything, and anything to do with PBM.
This was the received wisdom for many years. People thought, “Yes, you’ve got to use a red wavelength, you’ve got to use this particular near-infrared wavelength, because these correspond to the peak absorption of CCO, cytochrome C oxidase.” All the textbooks then were full of this. These are the particular wavelengths you want to use. Then, those studies were reappraised some years on and repeated.
Then, they found that actually the peak absorption for wavelengths for CCO was actually a blue wavelength, and it was around about-
Ari: Really?
Dr. Cronshaw: -445 nanometers. Yet, this wasn’t associated with a step increase in the production of ATP, and on the particular parameters they employed, they actually saw inhibition of production of ATP. Then, this whole issue to do with that specific pathway, was brought into question. Now, the reality is that the components that absorb the energy, this electromagnetic, what we call photon transduction, which is the conversion of the photon into something which is useful for the cell, is a fairly broadband effect.
It’s associated with what are referred to as transition metals, and transition metals in chemistry are things like iron, copper, magnesium, things like this. These are relatively broadband receivers of red to near-infrared energy. When it comes to pigmented materials, ferrous materials are pigmented. They form porphyrins, hemoglobin, flavins, a whole variety of other pigmented materials.
Then, there’s a host of other wavelengths which can be absorbed by dark pigmented bodies, which is referred to as dark body radiation. The concept then moved away from a specific photochemical process, to maybe there’s another mechanism that’s operating here. Then, newer concepts are introduced looking at the effects and the importance of water, and as possibly the primary, what they refer to as chromophore, which is, frankly, a bit of a silly thing to say about water, because water’s got no color, and chromophore literally means a color thing.
It’s the thing which absorbs the energy which is one of the contemporary theories. It’s not to say that Karu was wrong in regards to her work to do with the absorption. She just was wrong with the emphasis that she gave to it. Okay, so when you start to then look at an even broader aspect to do with mechanisms, then you realize there’s an awful lot happening, not just within the mitochondria, but also in other elements of the cell that many different wavelengths can be having many different effects.
There can be simultaneous effects in the cell membrane to do with iron gates, to do with nuclear chromatin, which is the stuff that makes up the nucleus, along with things like the endoplasmic reticulum, which is like the– To use an analogy, it’s like the Ford factory, for manufacturing proteins, as opposed to cars, and just this other internal aspects of the cell. There are many other photoreceptors.
Ari: Opsins.
Dr. Cronshaw: Yes. Well, you’ve got some opsins, you’ve got things called TRPVs. There are indeed a whole host of other aspects to it, rather than simply electron transport chain. Now, I’m not saying to you that the electron transport chain isn’t an important aspect related to the increase in activity you see when you expose tissues to energy at the levels that we’re using for photobiomodulation.
I’m just saying that, it’s a multi-plane response, in that, there are many different things that are happening within that cell. The consequences of that can be both within the cell, in the immediate vicinity of the cell, as well as the long distance effects. Then, you’re thinking, “Well, okay, this is really getting complex, not just a simple pattern.”
Ari: [laughs] I’m sure that’s what listeners are thinking right about now. Yes.
Dr. Cronshaw: The analogy I like to use is, it’s a little bit like, if you’ve got a whole bunch of musicians, just playing random notes, that’s what I would call disease, where, as opposed to everything working in beautiful harmony, the tissues, and the elements of the tissues, and the cells themselves are in this phase of illness, which we refer to as disease. PBM is like the conductor of the orchestra coming up to the podium, tapping his baton like this, and he gets the orchestra quiet, they tune, and then they start producing this beautiful music.
This is how PBM is working. It’s working on many different planes. It’s something which I would refer to as entrainment. All these different pathways can be happening simultaneously. It can be affecting many different targets. Simplistically, to say you’re just using a single wavelength to produce a single effect. Now, I’m sorry, I don’t agree, because I can produce PBM-like effects, or PBM effects with many different wavelengths. This has been demonstrated in literature.
There may be some which are better choices than others. Then, there are decisions to do with the symmetry, because with some of these wavelengths, there’s an awful lot of energy attached to that photon, and you don’t want to overcook your supper. Then, there are others which are very low energy, where it may take more to produce the effect that you’re seeking.
Ari: Okay. Can I interrupt one more time? I have one more letter of pushback here, which is a great job of presenting the case for many different wavelengths, creating either the same, activating the same, or similar mechanisms, or that it’s not so highly specific to very tight wavelength ranges that have these effects. Let’s present two arguments against this.
One is, let’s say, you use blue [unintelligible 00:29:20] wavelengths as let’s say, activating cytochrome C oxidase, which was, which had been historically thought to be unique to the red, and near-infrared wavelengths to some extent level. I’m going to present this argument, and then one more. On a practical level, we know that, for example, blue light at the level of the skin tends to have a pro-aging effect, or at the level of the eyes, tends to have a pro-aging effect in terms of promoting cellular damage, whereas red light seems to be beneficial, seems to create more of a healing effect, an anti-aging effect, anti-wrinkle effect. I’m sure you’ve seen in recent years that have used torches on the eyes, or at least one of– Two of the studies used torches on the eyes that had red light. I suspect you may disagree, but I suspect that if the same study were done with a blue wavelength of the same intensity, it would not have created a beneficial effect, but probably would have caused [unintelligible 00:30:24] harm. I’ll leave that sort of the provitamin of eyes and skin in blue versus red. [crosstalk]
Dr. Cronshaw: I can deal with the first before you go for number two. Because I’m the man for this. I tell you, Ari.
Ari: [laughs] Okay.
Dr. Cronshaw: I love it. It’s to do with photon energy. Now, the amount of energy attached to the photon, technically, we refer to as eV, which is the electron-volts. Now, Praveen Arany in his laboratory at the University in Buffalo, have one of his students, Young, do a study with some cells, which are called odontoblasts. These are the cells that form one of the structures in teeth, dentin.
What he did with these poor little odontoblasts, as he irradiates them, he expose them to different wavelengths at different dosimetry, where they altered the dose according to the wavelengths, so because the shorter wavelengths are more energetic than the longer wavelengths, they only provided half the energy for a blue wavelength, than they did with the red wavelengths.
Do you know what happened? They got exactly the same promotion and production of ATP with the blue wavelength, as they did with the 810. Out of this, they then came up with some concepts, which is a way where you can adjust the dissymmetry according to the amount of energy, which is in the number of electron-volts per photon.
Ari: That’s the Einstein’s measurement figure–
Dr. Cronshaw: That’s right. He came up with a way of calibrating the amount of dose you would give according to wavelength, because you produce identical effects. When you’re thinking about the damaging effects on skin, why is it producing damaging effects on skin? It’s because it’s generating what are known as reactive oxygen species, ROS, and the ROS that it’s producing, that’ll be a reflection of the dissymmetry.
If you’re to step the dose down to a much lower dose, then it’s not going to produce quite so much ROS, and then you might be seeing some biostimulatory effects, which is what Praveen’s students found when he was looking at odontoblasts. Whereas if you use the same dose with the blue, as you would as the red, which we know is beneficial. Well, the long short of it is, if you give an identical dose of the blue and the red wavelengths, and you don’t scale down the dose for the blue wavelengths, then because there’s so much energy there, then you’re going to generate a lot of ROS, which are very damaging to the tissues.
You’ll see aging of the skin. Similarly, you can see degradation of the blue receptors inside of your retina, which is specific blue wavelength ones that can cause you permanent optical damage. It’s been associated with a risk of age-related macular degeneration, for instance. It’s a dose-related response, which is related to the energy of the photon. It’s not because they’re bad photons, [chuckles] it’s just that the amount of energy per photon is maybe double what it would be if it was near-infrared one.
If you had to take the near-infrared one, and you’re then to double the dose, and expose that to your skin, then you’re going to be saying, “Actually, this is causing some tissue damage.” That’s exactly what Praveen did in one of his latest studies– Well, no, actually one of his early studies, [unintelligible 00:34:07], where he said, “Hey, with this 810 nanometer wavelength,” which is regarded as one of the good wavelengths for skin on the parameters that he was using, he was able to prove histologically, which is in tissue microscopy that he was seeing signs of damage inside of the skin when you use a certain amount of energy associated with that particular study.
When you step outside of the dissymmetry recommendation for that wavelength, and you put far too much of that wavelength there, it produced tissue aging and tissue-damaging effects. It’s not because the red wavelength has suddenly turned bad, it’s just that, then there’s a lot more of them there, and it can then start to produce these same adverse effects. You can produce comparable effects just by adjusting the dose. It’s not because they’re inherently bad or good. It’s all a reflection of the amount of energy attached per photon.
Ari: All right. I still have some resistance to this idea. I’m going to be honest with you because, for example, the overall body of literature tends to show, and with a wide variety of dosing parameters, that blue, for example, tends to inhibit collagen synthesis in the skin, whereas red light of varying parameters, you can certainly make it so excessive that it starts to because a negative effect. At most parameters tends to have a pro-collagen synthesis effect. Things like that make me think that there is something to the, as you call it, the magic photon idea.
Let me introduce this other idea. Let’s say that I have no resistance to the idea of everything that you’ve just presented. I’m certainly– I think that what you’re saying is probably broadly true, but as I said, I still think there’s maybe a bit more to the specificity of wavelengths and unique effects there. Maybe I’m wrong. You certainly know more than I do about that. [laughs] We’ll leave that aside for now.
The optical window, I know that you spoke to this earlier and you sort of made the case that this is much more complex than most people have historically thought of it. However, we can come back to this simple thing of let’s say you take a flashlight, a regular old flashlight, you shine it through your hand as most kids do, in a dark room. You notice that it’s predominantly red wavelengths that come through the other side of your fingers or the other side of your hand.
There is still this very clear, even if we accept the frame that all these different wavelengths, this is a slight misrepresentation of what you’re saying, or maybe a significant one, but let’s say we accept the frame that all these wavelengths have lots of overlap and activating some mechanisms and triggering similar effects. There’s still a big difference in terms of the penetration in tissue of these different wavelengths. Blue and UV, my understanding is that they stay, they don’t really penetrate beneath the skin to any significant degree. They can’t get beneath that barrier. Whereas you get into the reds and near-infrareds and you have a dramatic difference in the degree to which those wavelengths can penetrate below the skin deeply into the tissue.
Even if we were to accept, let’s say, the extreme frame of all wavelengths basically do the same thing, It’s just energy as packets of energy. Let’s say we were operating in that frame, there would still be this huge difference of the ability of wavelengths to actually penetrate through the skin into human tissue. Therefore there would still be a strong argument for red and near-infrared. Do you disagree with that?
Dr. Cronshaw: I’m not arguing with that at all. My bone I was picking was associated with this specific photochemical relation between a wavelength and the outcome. Really it’s energistics, because when you’re cooking, if you put things into a really hot frying pan, it’s going to burn fast. Whereas if you let it heat up slowly, it won’t. It’s a similar idea with these wavelengths. If there’s a lot of them, you’re going to produce a rapid effect, which can then be damaging. If there’s less of them, then you won’t.
I think optical penetration is indeed a key part of the decision process when you’re thinking about the applied aspect of PBM. What you will notice from point of view of the consumer is now there are all these multi-wavelength devices that are coming onto the market where you can mix wavelengths. You can have a bit of blue and a bit of red, a bit of near-infrared. You think, so why are they doing this?
I think there’s an awareness that some of these wavelengths have got some properties which can be useful, but perhaps in synergy, you can start to achieve multilayered effects. For example, blue wavelengths are the optimum wavelength for generating a chemical called nitric oxide, which is a very potent vasodilator, so it makes the blood vessels wider so you get more oxygen getting into the tissues. It does that by converting some nitrogen precursors called nitrosyls into nitric oxide, which then diffuses into the dermis and then you get these [unintelligible 00:40:18] effects from that very small molecule.
Blue wavelengths are regarded as the optimum for vasodilation. There’s enough energy there that they can be useful maybe for disinfection, which is why people use them for some skin disorders. If you combine that with a red wavelength, then you can start to get into the dermis, which is the next layer in of the skin, and you can then be producing simultaneous different effects. You can then be disinfecting the surface layer, maybe generating some useful biomolecules which will then include the blood supply to the base of the wound, say. With the red wavelength, you can be starting to produce some stimulatory effects which will then promote wound healing.
When you start to think in terms of 3D management of, say, an infected ulcer. Say you’ve got an infected ulcer in your tongue or something, you might want to have some surface disinfection. You want to maybe get some analgesia, some pain relief. At the base of the wound, you want some stimulation. Then the immune system is going to be more active, better able to deal with any pathogens, as well as going for good wound resolution. When you start to think in terms of a multi-planar effect, then you can start to see why this concept of mixing wavelengths can be quite interesting.
Ari: Let me, real briefly though, what I brought up before that there’s a pretty sizable body of literature that shows blue wavelengths have a negative effect on collagen synthesis. I’ve seen a number of, there are a number of different devices on the market, LED devices, and this has been true for a very long time, that some of these pad-style devices have blue and red wavelengths.
They never provide any particular sort of scientific rationale for why they’ve included blue in there, but it’s sort of like some of them incorporate yellow and green and sort of this vague notion that more colors are better for some reason, but there’s never any study that backs up those claims. If blue light– let’s say somebody’s using this device on their face, for example. You presented a case that talks about certain mechanisms, the nitric oxide blood circulation that may lead to blue wavelengths having a synergistic or beneficial effect, but somebody’s using a device on their face for facial skin anti-aging, and they’re getting pro-collagen synthesis effect from the red wavelengths, but now the opposite effect, an anti-collagen synthesis effect from the blue wavelengths.
LED devices
Dr. Cronshaw: It’s a dose-related response. It depends on the strength of the blue energy. Nobody’s going to start to use really powerful blue LEDs in close proximity to the skin, if they’re looking to stimulate [crosstalk]
Ari: I am aware of one LED panel manufacturer that has started to incorporate powerful LED in blue wavelengths.
Dr. Cronshaw: Oh, actually, may be, but–
Ari: It’s random, like one LED, blue LED here and there in a large powerful panel.
Dr. Cronshaw: Then if you’re looking at the overall dissymmetry, because it’s a dose-related response, it’s not the best wavelength for collagen stimulus, but neither is it automatically going to inhibit it if it’s at a very low dose. Then it’s going to have very limited penetration into the dermis where most of the fibroblasts, which are the cells that form the collagen, rest. It’s not the best choice. You have to be careful about the dose in case you overdo it, and then you’re going to produce these negative effects. Plus, the penetration of the photons isn’t going to be that great.
Yes, when it comes to facial aesthetics, I wouldn’t be charging out immediately to buy a blue LED face mask. Although those blue wavelengths may have some benefits if you’ve got some skin disorders. [unintelligible 00:44:35] I think this is a conversation where I think you can say, yes, blue wavelengths certainly do have hazards associated with them. That’s all to do with the amount of the energy that’s present, rather than inherently associated with the color.
The other aspect is the ability of the photon then to be able to deliver the goods into the deep layers of the tissue. Without a shadow of a doubt, if I was looking for something that was going to promote more youthful skin, I’d be going for a red to near infrared wavelengths and possibly a mixture of the two, so you can start to produce the desired effects. As for the blue wavelength–
Ari: Right. Again, and even in this framework, where, except the idea that many wavelengths have some activates or mechanisms, I still feel like we arrive largely back at the red and near infrared wavelengths just by virtue of sort of physics of photon penetration into the tissue.
Dr. Cronshaw: Yes, well, now I’m really going to upset you, Ari.
Ari: [laughs] Okay, go ahead.
Dr. Cronshaw: I think that when it comes to some specific aspects of PBM. The first law of photobiomodulation is that you’ve got to have the photon there to, at a sufficient dose, be able to affect the change which you’re seeking biologically. If you’ve got a wavelength which isn’t going to reach that target, then that’s just not going to work. Now this has come in from photochemistry. I think that’s absolutely the case.
However, there’s an awareness that things like LEDs, which are really quite superficial in terms of their penetration, they produce some quite deep tissue effects. You start to think to yourself, well, how can that be? The photons just aren’t getting down there. Even if you’re there for a long period of time, the amount of photons that’s penetrating into those deep tissue layers is slight. You may be talking 0.2 to 0.6% of the surface dose getting through to the deeper layers. So it takes a long time to get up to that critical threshold where you can start to produce some of the effects that you’re looking at.
It’s possible to do that, if you’ve got 20 minutes to an hour to sit around by an LED panel, you might start to get above that threshold. Along the way, you may be warming up some of the superficial layers of tissues, so you need to then use a lower output power LED, otherwise you might end up overheating some of the tissues.
Most of these things for extended use like the pods and things, more or less all of them about 25 to 30 milliwatt per square centimeter output devices, which is quite low. Now, so is there another pathway, so I asked myself this question, and I thought, well, maybe there’s another pathway. Mike Hamblin, and I’ll bring in an authority, as a supporter, I think I need supporters. You’re on a rampage, Ari. He would say, yes, well, you can produce systemic effects
Okay, so how does that work? Systemic effects are all mediated through skin. You can think of skin just as being this sort of layer of tissues to protect the insides of you from damaging environmental factors, whether it’s excessive ultraviolet or other factors which could damage your organs. Actually, skin is a very complex organ. It’s got a The neuroendocrine interface. So much so that one author of a paper I read recently suggested this is likely the brain [unintelligible 00:48:47]
Ari: That was a fascinating paper, by the way. Thank you for sending me that.
Dr. Cronshaw: [unintelligible 00:48:51] the neuroendocrine axis, because many of the elements, which are highly active in the nervous system, chemicals like serotonin, the happy drug, or adrenaline, which is another thing which is stimulates the nervous system, as well as dopamine, which is very important mediator of mood and focus and things, as well as some other important hormones like adrenocorticotrophic hormone or luteinizing hormone, and these are very powerful hormones that start to have distant effects. These are all produced in the skin. These skin generated mediators can then be picked up by the body and they can start to use distant effects.
That’s one pathway, but there are others as well. Some of the cell types inside of the skin have got a specific close relation to the nervous system. Melanocytes, which are the cells we more familiarly think have been associated with using pigments. On a nice sunny day, they’re triggered off, then start generating this pigment to protect your skin against excessive exposure to UV. That nice tan. They’re actually descended from the same cell line that an embryology results in the development of the entire nervous system. They’re what’s known as neural crest derivatives. Really it’s a highly specialized type of nervous tissue. There’s a very complex interrelation between melanocytes and their production of neurotransmitters, because they’re not just producing melanin, they’re also producing these other things, as are some other cell lineages all within the skin.
Then beyond that, there’s other pathways associated with nerves that actually get into the skin. It’s been found that the outer sheath of some nerves contains something called myelin. We used to think this is a bit like the plastic coating around an electric cable, just to insulate. Actually myelin’s got a hidden feature in that it’s been found that myelin, because of its optical properties, can act just like a photo-optic guide. It can help transmit the photons along its length. This has been measured.
They found that naturally axons, which are nerve cells, produce these things called bio-photons. This is where energy, as it’s processed, can then release little packets, tiny minuscule amounts of little sparkles of photons, which are then transmitted along the myelin. This is a super fast, it’s going as fast as the speed of light, which is then going along to be received at the cell body.
This is associated with some changes in nuclear transcription factors. This has been associated with an increase in mitosis. It’s been proposed as being associated with being an important element in nerve regeneration. It may have a whole host of other effects, because the body is full of light-sensitive molecules. Even the deep tissues, like your heart, things that just never see the light of day in normal circumstances, these are very light-sensitive because they have inherent to them what are known as opsins.
Opsins are related to the same sort of thing that you have in your eye. We have opsins and rhodopsins, which help us to see, just as I can see you now, but there are lots of other types of opsin where the stimulus doesn’t produce a visual response, so the cells don’t have eyes, as it were, but they are very responsive to light.
This is an area which Ann Liebert has written about, and her group in Sydney, where they’re looking at other mechanisms associated with photobiomodulation. This is so remarkable because we’re just at a point where we’re so far moving away from this previous idea of it being purely a photochemical response inside a specific molecule inside of the mitochondria.
We’re looking at all these other possible mechanisms that help explain something which is otherwise now inexplicable. That you can get someone who sticks some really low-power LEDs on top of their head and they can start to treat their Parkinson’s disease. The photons themselves, how are they getting into the brain? it’s been suggested maybe this may be in part a systemic effect to do with the generation of these neurochemicals. It may be due to hidden transmission pathways, which could be associated with myelin. We just don’t know.
Ari: That’s, I think, a remarkable idea that I have not encountered anywhere in the literature as of right now. That not only this distinction between systemic versus local effects, sort of are you delivering photons through the skin, through, let’s say, the bone, in the case of through the brain, and then brain tissue where those photons are then triggering this photochemical reaction in the cells, this direct photon cell or photon mitochondria reaction? Or are you triggering systemic effects through the skin, through the blood, and now things are going systemic and altering different parameters in the blood or maybe the nervous system?
Now this additional layer, which is potentially how photons are interacting with myelin sheaths, and maybe these photons are actually able to penetrate much more deeply than we currently conceptualize through these sort of hidden pathways that we’re not really aware of currently.
Dr. Cronshaw: Absolutely. It sounds like cells have got cable. [laughs] It’s a hidden mechanism, and this whole concept I think is amazing because it helps then to explain what’s otherwise inexplicable as to how it is that a surface application of a really weak source like an LED can start to produce some very deep effects.
In truth, it’s probably a combination of all of these different things. There’s probably some photons getting through into the dermis from an LED with the protracted exposure along with a multilayered systemic as well as possibly other mechanisms. Hair can be a photo-optic guide. Teeth can be a photo-optic guide. We are inherently all very light sensitive. All of our bodies are biologically light sensitive. It’s not just–
Ari: Can I ask one thing that makes me somewhat skeptical of this idea?
Dr. Cronshaw: Yes.
Ari: It’s not necessarily incompatible. I’m sure that there’s probably ways that both things could be true, but what makes me skeptical of the idea that, let’s say, these very low-power devices could be delivering significant quantities of photons sort of directly to those tissues is just the sunlight. If it were the case that let’s say our brain could receive significant quantities of photons through such a low, low-power device, that effect a measurable change, then wouldn’t we just by going out in the sun for half an hour or an hour– I’m a surfer, for example, so I might spend sometimes three plus hours outdoors in the bright sun. If I’m in Costa Rica, there’s an enormous dose of very intense sunlight. Wouldn’t my brain be getting bombarded with just maybe vastly too much photonic energy in a case like that, if it were so sensitive to even very low intensity light?
Dr. Cronshaw: The evidence shows that some ambient light, sunlight, can be producing biologic effects. People suffer from SAD, seasonal adjusted disorder, where in the winter months, they’re not getting enough exposure to light, then they start to suffer from mood disorders. Then a little bit like bears, they start to hibernate, their brains, really, they’re not very active.
The body being the beautiful self-regulating machine that it is responsive and defensive. There are mechanisms inherent which then help protect us against excessive stimulation. When you start to have saturation of large areas of the tissue, then this can then not produce the positive effect that you’re seeking. Now, this has been found in some of the brain studies where they’ve been looking at just generalized helmets that treat the whole of the cranium, as opposed to things which then are targeting specific areas in the brain. They see that the one where they’re targeting specific areas is producing the positive effect, whereas when they’re radiating everything, it doesn’t produce that same positive effect. It doesn’t produce any harmful effects, but it will not produce the desired positive effect.
I think when you start to split between the management of disease and living in health, I think a little bit of ambient light is a great thing. It’s undoubtedly associated with human health and wellbeing, but you can have too much of a good thing. That tends to be self-regulating, because if you do, and you don’t have enough skin protection on there, you get cooked, and you know it. You have to protect your skin against getting sun-aged, and you can end up developing various unpleasant skin conditions, including various carcinomas and things.
The dosimetry element is still there. As far as producing the happy events, well, everybody knows in a bright sunny day, you feel good. That’s serotonin. That’s why people are happy. You live in one of the happiness capitals of the world at the moment. You’re in California, so it’s sunshine. This is something which is a mood enhancer. Whereas those who are permanently, as I am at the moment, looking out the window in the frozen north of the south of England, we have very little exposure to light. I go to the office, I do my work, and I come home and it’s dark again, and the amount of exposure and light I get is to some artificial light instead of that beautiful natural stuff.
Natural light itself, of course, is a mixed bag between ultraviolet, which can be harmful, the visible spectrum, which is mostly in the blue to red wavelengths, through to the infrared, and with only a tiny amount of UV present. When you’re thinking about using scientifically as a medicine light, which is what photobiomodulation is all about, then how good is ambient light?
They used to use ambient light years ago in the sanatorium in Switzerland to help people recover from tuberculosis. They had these things like sun lounges. The original work that was done by Finsen, who won the Nobel Prize for this, was with bright, intense light in order to kill off tuberculosis in the skin. He was into high-intensity antibacterial effects, but I presume he also had a photobiomodulatory effect, which would mean some attenuation.
I think we could go around the houses on this one, Ari, but I think, yes, light is terribly important for health. That’s indisputable. If you want to start to produce specific effects for specific occasions, like a sports injury, or to help you with a particular illness, then PBM, selecting your tool and getting the dosimetry right, that’s more like medicine.
Ari: Dr. Cronshaw, I’m really enjoying this discussion. I can’t wait to dig into this more with you. We’ll have to cut this one off here. I would love to pick up tomorrow, if that’s a possibility for you, if you have another time slot at the same time tomorrow morning. We can discuss that after. I’m very interested in this idea that you keep touching on and I keep preventing you from really going into, which is around entrainment. I think we need to get into that. I’m very curious to see if that relates to pulsing in any way, as some people have proposed theories related to that. May or may not. I’m curious to see what your answer is.
What else? Lasers versus LEDs, the biphasic dose response, and the multiphasic response. So much more to get into, and then we need to get into the philosophy of care, as you called it. Your practical framework, the how-to guide of how you actually do this. There’s just so much to talk about and so much complexity. With all of your accumulated knowledge and the way that you address layer by layer, piece by piece of this story, it’s taking us a long time to get through each individual topic, but I think that it’s so important to really apply this level of nuance and elaboration on all these issues. I think the big lesson from what you’re trying to communicate, I think the meta lesson is the story is really much more complex than most people realize.
With that said, I hope everybody is enjoying this, geeking out on all the complexity of photobiomodulation science. Dr. Cronshaw, I can’t wait to continue the conversation.
Dr. Cronshaw: It’s going to be my pleasure, Ari, but I think it was Einstein that said any fool can make something more complex. I hope by the time we’re finished, we’ll have simplified this. For those who are listening, if you can just come along through the journey at the end of it, the view from the top is beautiful.
Ari: Yes, beautiful. Beautifully said, and I love that quote from Einstein. Thank you so much, Dr. Cronshaw. I’ll be in touch with you, so we’ll arrange the next one.
Dr. Cronshaw: Okay.
Show Notes
00:00 – Intro
01:36 – Guest intro
05:00 – The different wavelengths
22:34 – How PBM works on a biochemical level
47:35 – LED devices
Recommended Podcasts
