The Peter Attia Drive
#326 - AMA #65: Red light therapy: promising applications, mixed evidence, and impact on health and aging
Mon, 18 Nov 2024
View the Show Notes Page for This Episode Become a Member to Receive Exclusive Content Sign Up to Receive Peter’s Weekly Newsletter In this “Ask Me Anything” (AMA) episode, Peter dives into the world of red light therapy in response to frequent questions from listeners. Peter provides a comprehensive exploration, starting with the basics of red light therapy and why it’s getting so much attention. The conversation examines the latest data on various applications, including aging, skin health, acne, wound healing, hair loss, eye health, exercise performance, metabolic health, weight loss, inflammation, injury recovery, and menstrual cramps. Peter analyzes the scientific literature on each use case and concludes with a summary table that provides an easy-to-follow breakdown of the potential benefits of red light therapy across these areas. If you’re not a subscriber and are listening on a podcast player, you’ll only be able to hear a preview of the AMA. If you’re a subscriber, you can now listen to this full episode on your private RSS feed or our website at the AMA #65 show notes page. If you are not a subscriber, you can learn more about the subscriber benefits here. We discuss: Overview of topics and the motivation behind exploring red light therapy [1:45]; The basic science of red light therapy [3:15]; The unique penetration properties of red light [6:00]; What happens when tissue is exposed to red light [9:30]; Exploring red light therapy’s potential to combat aging [11:00]; Red light therapy for treating acne [13:00]; Red light therapy for aiding in wound healing [18:45]; Red light therapy for hair loss: promising benefits and practical advice [24:15]; Analyzing the evidence of a positive or negative effect of red light therapy on the eyes [28:00]; Red light therapy’s impact on performance and recovery [30:30]; Red light therapy’s impact on metabolic health: analyzing the limited evidence for improved glucose metabolism [32:45]; Red light therapy for weight loss and targeted fat reduction [36:45]; Red light therapy for inflammation, chronic pain, and injury rehabilitation [41:00]; Red light therapy as a treatment for menstrual cramps [43:45]; Summary: promising applications of red light therapy, unsupported claims, and costs to consider [46:45]; and More. Connect With Peter on Twitter, Instagram, Facebook and YouTube
Chapter 1: What is red light therapy?
Peter, welcome to another AMA. How are 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 patients as well.
And so we compiled all these questions and through this conversation, hopefully going to cover what red light therapy is. how it can work, deep dive into some various claims out there around red light therapy.
Chapter 2: How does red light therapy combat aging?
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?
Two unrelated things. I notice you have a little visitor for the podcast today hanging out with you there. Hopefully he's interested and this is something he'll like. And secondly, I would add that my wife is specifically asking me these questions. So she's very keen to buy a whole bunch of red light things.
Chapter 3: Can red light therapy help with skin health and acne?
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 if there's value there, where it is. 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 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?
You can't do this without at least having some understanding of the physics and the principles that define light and waves come up over and over and over again as you try to evaluate the plausibility of the claims that are made here. So when we're sitting here looking out at the world, we're looking at light and there's visible colors of light. Maybe I should take a step back.
Chapter 4: What are the benefits of red light therapy for wound healing?
Light exists as waves and they're very short waves to be clear. So sound waves are really, really long. Light waves are really, really short. And then obviously waves can get much, much shorter and you can get into UV, which we've talked about 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 wavelengths get shorter, the energy gets more powerful. But if we just focus on light, visible light runs the gamut from about 380 nanometers, 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, they're mostly talking about light that is in that very narrow band.
So for example, again, a white light is giving you all mixed across that entire range. Red light would be more narrowly focused. It's also important to understand that, and we'll talk about this a little bit today, phototherapy in general involves wavelengths across that entire band of visible light, but it also includes something called near infrared.
So that basically runs the gamut from about... 400 to 1100 nanometers. So I think the easiest way to think about this is red light therapy, which runs about 620 to 780 nanometers, and then near infrared, which is right adjacent to that, the next thing up in terms of length, which is about 790 to 1400. So again, if you forget everything else, just remember,
Chapter 5: Is there evidence for red light therapy in treating hair loss?
When people talk about red light therapy, they're talking about wavelengths that are just in that red visible area of 620 to 780. And then often they talk about near infrared as well, which is not visible. To be clear, you don't see it, but it's just a little bit longer, 790 to 1400 nanometers.
We'll come back to this over and over again because there are some instances where the fact that you can't see it might actually make it a little more 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?
Chapter 6: How does red light therapy affect exercise performance and recovery?
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, And you remember that the 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 more so than other forms of visible light. 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 kind of a function of how the light beams are organized.
Chapter 7: What is the impact of red light therapy on metabolic health?
So what is the amount of coherence, which is how much do the wavelengths line up with each other? So if the wavelengths are all coherent, the peaks and valleys are in the same place. It's going to have more penetrance. And then what's the extent to which they're all aligned in the exact same direction? That's called collimation.
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 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, which of course, there's a very clear relationship between them. And of course, broadly speaking, energy matters as well. So
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.
Chapter 8: Can red light therapy reduce inflammation and chronic pain?
If red light is being delivered by LEDs, which is the most common way that it is, it's going to be able to penetrate about two to three millimeters into skin. Now, infrared light can go a little bit deeper, because remember, it's a longer wavelength, and it can reach probably 5 to 10 millimeters.
Now, if red light is delivered by a laser, because again, you now have a more focused form of light energy, it could penetrate significantly higher than that. It could go from 1 to 4 centimeters. So again, keep in mind, the way that the light is organized plays a significant role in the depth that it can penetrate.
Now, if you start to think about some of the applications we're going to talk about, when you start to think about red light therapy, just keep in the back of your mind, if something can only penetrate one to three millimeters, it's going to be difficult for it to have some of the profound effects that are sometimes claimed.
Even if something can penetrate 10 millimeters or a centimeter, which would be quite deep, it's not clear that that's going to be able to have a significant effect. 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 the various claims and where this could be beneficial and 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. And so the absorption of light by these photosensitive molecules, which are called chromophores, cause 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 effect of the biologic impact of red light.
So red light and near-infrared wavelengths do seem to excite cytochrome C oxidase, and its activity then increases subsequent 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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