Transcription
Hey everyone, welcome to the Drive podcast. I'm your host, Peter.
[Music]
AA Peter, welcome to another AMA. How you doing?
Good, thanks for having me back.
Anytime, anytime. So today's AMA, we are going to focus on a single topic, which is red light therapy. This is something we get asked about a lot, not only questions from the website and subscribers, but I know through your patience as well. And so we compiled all these questions and through this conversation, hopefully, we're going to cover what red light therapy is, how it can work, deep dive into some various claims out there around red light therapy. This can include potential effect on skin health, wound healing, hair loss, eyesight, exercise performance and recovery, metabolic health, fat loss, inflammation, chronic pain, and a lot more. So with all that said, anything you want to add before we get rolling into it?
To unrelated things, I noticed you have a little visitor, uh, for the podcast today hanging out with you there. Um, so hopefully he's interested and this is something he'll like. Um, and secondly, I would add that this, my wife is specifically asking me these questions. So, um, she's, uh, very keen to buy a whole bunch of red light things and I asked her to just hold off until we did the research for this episode so that we could at least have a sense of, of, uh, if there's, uh, if there's value there, where it is. I don't, I don't know if she's a subscriber though. So if she's not, this might be the one that she subscribes for.
I, I respect that. When your wife asks you medical questions, you say, "Let me send you a podcast episode" instead of telling her the answer, like everyone else. So it's good to know you practice what you preach, even through your direct family.
Okay, first question. I think it's going to be helpful to just explain when we say red light therapy, what does that even mean?
Yeah, um, I, I, you, you, you can't do this without at least having some understanding of the physics and the principles that that define light and waves. Waves come up over and over and over again as you try to evaluate the plausibility of the claims that are made here. So, um, so when we're sitting here looking out at the world, um, we, you know, we're, we're looking at, uh, light and it's there's visible colors of light, right? So what the, and maybe I should take a step back, right? Light, um, exists as, uh, waves. Um, so the, and they're very short waves, to be clear, right? So, so sound waves are really, really long, uh, light waves are really, really, um, short. And then obviously waves can get much, much shorter and you can get into UV, which we've talked about in in detail on a previous podcast, and then even shorter than that would be X-rays, and then even shorter than that are gamma rays. So as, as light, uh, w-, as wavelengths get shorter, the energy gets more, uh, powerful. But if we just focus on light, visible light runs the gamut from about 380 nanometers, um, which would be purple-ish, and then all the way at the longest end, about twice that, 780 nanometers, is where red light is. So when people talk about red light therapy, um, they're mostly talking about light that is in that very narrow band. So for example, again, a white light is giving you all, you know, mixed, mixed across that entire range. Red light would be no more narrowly focused. Um, it's also important to understand that, and we'll talk about this a little bit today, phototherapy in general involves wavelengths, um, across that entire band of visible light, but it also includes something called near infrared. Um, so, um, that basically runs the gamut from about 400 to 1100 nanometers. So, um, I think the easiest way to think about this is red light therapy, which runs about 620 to 780 NM, and then near infrared, which is right adjacent to that, the next thing up in terms of of length, which is about 790 to 1,400. So again, if you forget everything else, just remember when people talk about red light therapy, they're talking about wavelengths that are just in that red visible area of, you know, 620 to 780, and then often they talk about near infrared as well, um, which is not visible, to be clear, you don't see it, um, and it's just a little bit longer, 790 to 1,400 nanometers. This, again, we'll come back to this over and over again, um, because, you know, there are some, um, instances where the fact that you can't see it, uh, might actually make it a little more, uh, dangerous.
Double-clicking on red light therapy, can we explain a little bit more about what is special about it and why there's so much emphasis on it as talked about for the various claims that we'll speak about today?
People who listened to our podcast on ultraviolet light may recall a distinction I made between UVA and UVB, which came down to the degree of penetration. And so similarly, when you think about red light therapy, um, and you remember that the, uh, longer a wavelength, the more it can penetrate, albeit with less energy, what makes red light interesting is it is sort of at this sweet spot where it has some capacity to penetrate at more so than other forms of visible light. So, so you, you know, that's, that's sort of part of what makes this interesting. Now, the exact depth that's reached by the red light or the near infrared is is kind of a function of, um, how the, how the light beams are organized. So, what is the amount of coherence, which is how much do the wavelengths line up with each other? So if, if the wavelengths are all coherent in the exact same, um, uh, uh, the peaks and valleys are in the same place, it's going to have more penetrant. And and then what's the extent to which they're all aligned in the exact same direction, uh, that's called colation. So in other words, the light isn't spreading, but rather it's all pointed in the exact same direction. And then finally, you have the intensity. And we'll, we'll talk a little bit about the difference between watts and joules because if people are looking at these devices, sometimes they give you information in watts and sometimes they give you information in joules. Of course, um, there's a very clear relationship between them, um, and and of course, but but broadly speaking, energy matters as well. So, um, when you take all of that into account, though, the really important principle that I think gets perhaps missed when people evaluate these things is that for the most part, red light can't penetrate nearly as much as people think it can. Okay? So if red light is being delivered by LEDs, which is the most, most common way that it is, it's going to be able to penetrate about two to three millimeters into skin. Um, now, um, infrared light can go a little bit deeper because remember, it's a longer wavelength and it can reach probably five to 10 millimeters. Now, if red light is delivered by a laser, because again, you now have a more, um, focused, uh, form of, of, of laser of light energy, it could penetrate significantly higher than that. It could go from one to four centimeters. So again, keep, keep in mind, um, the, the way that the light, um, is organized plays a significant role in the depth that it can penetrate. Now, um, you know, if you start to think about some of the applications we're going to talk about, um, when you start to think about red light therapy, um, just keep in the back of your mind, if something can only penetrate one to three millimeters, um, it's going to be difficult for it to have some of the profound effects that, um, are sometimes claimed. Even if something can penetrate 10 millimeters or a centimeter, which would be quite deep, um, it's not clear that that's going to be able to have a significant effect. And so as a general rule of thumb, the more superficial the application, the more plausible I think it's going to be.
As we go through these, last foundational question before we get to to the various claims and where this could be beneficial or not, is in general, what happens when the tissue is exposed to red light?
This is an important and, as you said, foundational question. So to have any biologic effect, the light needs to be absorbed by some photosensitive molecule within the cell or tissue that it's hitting. Um, and so the absorption of light by these photosensitive molecules, which are called chromophores, cause, um, a localized chemical change or a photochemical reaction. Now, the most interesting of these is probably something called cytochrome C oxidase, or CCO. It's a component of the electron transport chain within mitochondria. And generally speaking, most people who are proponents of red light therapy point to cytochrome C oxidase, or CCO, as the main target and therefore the mediating, uh, effect of the biologic impact of red light. So red light and near infrared wavelengths do seem to excite cytochrome, um, C oxidase, and its activity then increases subsequent, uh, ATP production. Conversely, blue and green wavelengths, remember these are shorter, less penetrant, but more powerful, seem to decrease the activity of CCO and subsequently decrease ATP production.
Now, kind of getting into various claims of where red light therapy can be beneficial or not, I think it'd help to maybe start with what do we know about the idea that red light therapy can combat aging as a whole?
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