What's the deal with red light therapy?

18:40Perry Wilson:I also think there's a sort of interesting thing here around youth sports that, you know, kids used to do more variety of sports. The increased youth sports specialization has pushed kids to do more and more and more of one sport early on when your ligaments and so on are more susceptible to like overuse. So I think that is part of what we've seen more of this in high school kids over time.

19:05Emily Oster:And that's it for the health news of the week. After the break, what's the deal with red light therapy?

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23:50Perry Wilson:So let's talk about red light therapy. So for people who are not on the internet, red light therapy refers to the idea of putting red lights, lights with a particular wavelength. We'll get into that on your face, your wound, your body, your brain, in a helmet, in some way exposing some part of your body to this light. And it's supposed to improve a wide variety of things. So the way I would like to structure this is I want to talk about why we might think this would work, but then really think about the relationship between biological plausibility and like, is it likely this actually works for the things that people say that it works for?

24:30Perry Wilson:But then also, you know, is buying that red light mask on Instagram, like the way that I should implement this, even if it works. And I think those are always really important benchmarks in these discussions. Like, is it plausible? Are we seeing it in studies? Is it actually something you could implement on your own? So if that works for you, I want you to tell me why we would think putting lights on our face is good or anywhere. And why, what is this thing?

24:55Emily Oster:I thought we might get through an episode without talking about mitochondria, but here we are. So far, no. So far, no. So biologic plausibility, this is like the central technique of wellness influencers to sell you on something, is to convince you that there is a biologically plausible mechanism and then jump to the conclusion that because there's plausibility, it must work. And I think if we can teach people anything, it's that you have to prove that. Biologic plausibility is table stakes for something that you're going to invest in for your health. But let's talk about the table stakes. Because at first you hear it and you're like, I'm going to shine red light on my skin.

25:32Emily Oster:Like what? Of course that doesn't work. That seems ridiculous. It's not actually ridiculous. So I'll try to go through this very quickly. First, a bit of physics. The wavelength of light.

25:43Perry Wilson:I'm sorry, but when somebody starts with, I'm going to go through this quickly and then begins with just a bit of physics. Perry, let's do it. Do it quickly. Just a tiny bit of physics now.

25:52Emily Oster:A little bit. All right. Let's start with the Big Bang. I'm going to start with the Big Bang. Okay. The universe was hot and dense. Okay. No. Skip forward. Light. Light has wavelengths. Longer wavelengths are redder. Shorter wavelengths are bluer. As wavelengths get longer, you go in the visible light spectrum, you go from blue to red to infrared. And the longer the wavelength is, the easier it passes through stuff. The longest wavelengths that you're typically exposed to are probably radio waves, which are very long, much longer than infrared light. And they go right through your walls and through your body and all these kind of things.

26:28Emily Oster:Right. So wavelength matters. Because of that, some wavelengths of light can actually get below the surface of your skin and even slightly deeper. We'll talk about that. OK. In your cells, there are mitochondria, the powerhouse of the cell, as you learned about in high school. What's actually happening in mitochondria is called aerobic respiration. Aerobic means having to do with air, but in this context, it means oxygen. So mitochondria are the things in your cells that metabolize the oxygen you breathe and help turn it into energy by combining it with byproducts of glucose and other energy-containing molecules.

27:07Emily Oster:They are burning the gas of your cells, basically, to make the ATP that is the energy of your cell. And this is a very complicated process. In the mitochondria is a protein called cytochrome C oxidase. And cytochrome C oxidase is the final step that the mitochondria needs to transform glucose and all the other sugars and other sources of energy you need into ATP, which is the energy your cells use. It's very critical. If you were to try to kill someone with cyanide, the way you would kill them is because cyanide binds irreversibly to cytochrome C oxidase, shutting it down, which shuts down all your mitochondria and all your cells start to die.

27:51Perry Wilson:Fascinating.

27:52Emily Oster:Okay. Very important. Okay. Noting that. In 1981, a paper comes out entitled cytochrome C oxidase is a possible photoreceptor in mitochondria. And Emily, in layman's terms, what do you think that means? No,

28:08Perry Wilson:I'm just going to kill you with cyanide, Mary. And that's what I'm taking from this conversation.

28:14Emily Oster:All right. What that means is that this is a protein that light interacts with, which is odd because most of the proteins that light interact with in our bodies are in our eyes and like some in our skin to help make vitamin D and stuff like that. But a little bit unusual to see in mitochondria. And I suspect it probably comes from the bacterial that the mitochondria were in our deep evolutionary history or something. So in a Petri dish, it has been shown that certain wavelengths of light interact with cytochrome C oxidase. And this begins the entire red light therapy movement, essentially. What happens when you shine red light, certain wavelengths, so we're talking wavelengths of somewhere between 600 and 800 nanometers, there's different frequencies that seem to work better and worse is that it changes the electrical state of cytochrome C oxidase and makes it work a little bit more efficiently.

29:12Emily Oster:Now, you're going to see influencers online tell you that it kicks out nitric oxide from cytochrome C oxidase. I actually don't think that's true, but we don't have to go into that. But it clearly does ramp up in a Petri dish. It ramps up the production of ATP. That's the fuel of yourself by shining light on this thing. and that's interesting and surprising that you could give a little light and you would slightly increase ATP production and then we're off to the races.

29:40Perry Wilson:Right. And I think then because ATP, just to sort of step back, because ATP is such an important driver of our cell and driver of all kinds of things, I think that is why this has become a space where we're evaluating the potential of this therapy for like almost anything because it's like ATP, we're using that all the time. That's like how your cells... Yeah, if you don't

30:01Emily Oster:have it, you literally die.

30:02Perry Wilson:Right. So before we get into the details, I do want to like double click on the, you know, this is a really cool paper from 1981. But the beginning of the summary of this paper says the effect of light on respiration of intact mouse liver mitochondria was examined at various temperatures using various inference filters. And what that means is in this study, you know, it's not that they went to people and they did stuff to them and they saw how it, It's they have some mouse liver mitochondria in a Petri disc and they're putting light on it and then they're seeing what happens. And it's super, super cool science and very interesting biological plausibility, but not some direct like we shine light on people and things happen.

30:44Perry Wilson:And that's what you then need to evaluate in these studies.

30:47Emily Oster:Right. So, again, the way that wellness space tends to work, like if I wanted to be a very popular wellness influencer, I would be like, look at this. It's amazing. It increases ATP by 20%. And here, buy my thing, and it'll increase your ATP by 20%, and that'll make you younger and more virile, and everything will get better.

31:05Perry Wilson:There's a really big gap between those two. You got to tie those things together.

31:09Emily Oster:Let's tie them together.

31:10Perry Wilson:Let's tie them together. So actually, because of this ATP is so important, there are many, many, many, many, many things which people will claim. And so I think we should start with actually something that is real. There is at least one thing in this space, I think, which is called photodynamic therapy, that is a real and a positive red light effect. So tell me, positive effects.

31:34Emily Oster:Yeah. Photodynamic therapy, I mean, this is definitely real, but it's definitely not the wellness space. So what photodynamic therapy is, is a combination of light plus some chemical to affect a change in the cell. So this is usually used for skin conditions like actinic keratosis, which is a precancerous skin condition. You put a special cream on the spot on the skin, the cells sort of take up that cream, and then you shine light of a certain frequency on that area. And the cream undergoes a chemical reaction that creates a toxic byproduct. And the idea is that, you know, like a chemotherapy, the cells that took it up get killed because these are precancerous cells that you're trying to kill.

32:19Emily Oster:And because light, as we pointed out, doesn't penetrate that far beneath the skin. We should probably talk about how much it penetrates. You limit the toxicity of that therapy. So, like, yes, these things exist. Obviously, that's cool. It's like a combination of light and medicine. I like it. But that's not really what people are talking about online.

32:39Perry Wilson:Yeah, and that's something that if you had this condition, your doctor would potentially prescribe this, but it is not something you would do on your own because there's a weird dry spot on your face.

32:48Emily Oster:Exactly. I mean, I think where the bulk of what I'm seeing online is about skin, skin related stuff, wrinkles and discolorations and acne and things like that. So, Emily, I know you've thought about this a bit. What does the evidence suggest in terms of red light affecting meaningful changes in people's skin? I know you don't care about it. You've told us you don't care about wrinkles, but I do.

33:13Perry Wilson:So I think this is a very interesting space because it's actually quite hard to study. So imagine that I do something to you and I tell you like, here, Perry, here is this cream, this mask, this whatever. like use it on your face every day for, you know, three weeks and then come back and tell me how you feel like your face is. Okay. I could give you almost anything, a bottle of aquaphor, some, you know, Cetaphil face wash, a cream glow recipe from my kid, whatever it is. And you would come back and you'd be like, I think my face looks amazing. And that's called the placebo effect. Basically we are really susceptible to like the suggestion that something might work.

33:55Perry Wilson:So one of the issues with many of the studies of these masks or these kind of red light wrinkle treatments is that they are using as the perceived outcome, either the sort of evaluation of the individual or an evaluation of an investigator who kind of knows, potentially knows whether somebody was, in fact, using the red light mask. And so what the ideal approach to a study like this is to have a blinded approach where some people get red light therapy and some people get a placebo. But the placebo needs to actually seem like red light therapy. But since the therapy is just putting light on your face, it's actually very hard to have a placebo form of this.

34:37Perry Wilson:It's not like a pill where you can give them a pill and it looks the same and then you can have a true placebo. So I think a lot of the studies of this, just like before we get into the results, a lot of them are really pretty limited because it's very, very difficult to have what's called a sham placebo.

34:54Emily Oster:But you could have a blinded evaluator. So instead of the person that did the therapy, just have their picture or something and have some third party decide if their skin looks better or not, right?

35:05Perry Wilson:And so the better studies do that. But even there, you want a sham placebo because how do you know the effect is red light rather than something else, right? And so, I mean, maybe that doesn't really matter, but if you actually care about the sort of biological plausibility and linking that to these effects. We would like to test this particular, you know, this wavelength or this, you know, this particular treatment. And that's very hard to do without having a true placebo because maybe there's an effect, but maybe it's not really about the red light. Maybe it's about the laying down and having the warm stuff on your face.

35:41Perry Wilson:Like, I don't know.

35:42Emily Oster:Right. Or the patient or the participant in the trial kind of knows they're getting the red light because as you say, it's hard to placebo and they like wash their face more or something after. It was more moisturizer, whatever it is.

35:52Perry Wilson:So when we look at these studies, there are a small number of mostly very small sample size RCTs, some of which show maybe some small impacts of some red light therapies in sort of different directions. I would say my take on this is the effects are generally very small and the dosing is really inconsistent. And in many of the cases, it has the problem that, you know, there's 12 different things we can measure about your wrinkles and, you know, two of them, it kind of seems to work and most of them it doesn't. So this is not a statistically very compelling literature. I'm not sure that I would say we completely rule out any possible small effects on wrinkles or other sort of skin elasticity, but, you know, it's not Botox for getting rid of your, I mean, just realistically, this is not very large impacts.

36:46Perry Wilson:And I think it will be hard to study. I mean, I think it's not, I'm not sure we're going to get really super to the bottom of that, just because of this sham, because of the sham problem.

36:55Emily Oster:Let's move off of skin then a little bit to some of the other claims that people talk about.

37:01Perry Wilson:One I was extremely interested in is wound healing, which feels like, again, a more directly medical thing, but maybe something where there's a little more positive evidence, maybe.

37:14Emily Oster:Maybe, but not really. Yeah, so I dug into this a little bit. Most of the literature here actually comes from real medical device studies, not so much the wellness space. So we're talking about lasers being used to treat diabetic foot ulcers and things like that. There was one decent randomized trial. I mean, also small, 30 people, but nicely blinded in this case. These were patients with diabetes who had diabetic foot ulcers, and they did demonstrate some accelerated wound closure through the use of this very specific 904 nanometer laser that is not available to be purchased anywhere. This is a medical device that is used in certain doctors' offices.

38:02Emily Oster:This is one of the like meta problems of red light therapy is that like red light, this isn't like a chemical, like an antibiotic or a chemotherapy drug that is difficult to synthesize and, you know, requires a giant lab. Like you can buy a red LED at, you know, I was going to say Radio Shack, but you can't because Radio Shack's out of business. You don't have that anymore. Home Depot, Amazon. Home Depot, Amazon, Timu. And you can buy these things for, you know, cents.

38:31Perry Wilson:So who does that sell this?

38:32Emily Oster:I bet it does. It definitely does. But you know what I'm saying? So you do also have to be careful when influencers are like, oh, look at this study. And it does show this good. It's good for wounds. And they're using like this very specific type of thing that is not necessarily what you're buying online. Yeah. Again, is there plausibility? A little bit. But I don't think this is something that you really should be strapping to open wounds or shining at open wounds necessarily. I think you should be using your triple antibiotic ointment and bandaid and a bandaid. Yeah. Let's move off of wound and go to like weirder, weirder stuff.

39:12Emily Oster:Let's go to the head, because I saw some people arguing that this red light therapy might improve cognition or thinking. No, I am skeptical, Emily.

39:23Perry Wilson:So this is a place where I think the biological plausibility kind of falls down, right? So you talked about sort of different wavelengths at the beginning and the idea that this sort of might work by wavelengths, kind of these longer wavelengths being able to penetrate your skin. It's not really obvious that those wavelengths could penetrate far enough to be into your skull. I think there's like disagreement about surely some wavelengths, like radio waves, go long enough, But it's not clear that even at the upper end of the wavelength of red light that they can actually get into your brain.

39:56Emily Oster:Yeah, I tried to look at this. And for red light that you can see, so not infrared, but kind of deep red light that you can see, the penetrance into the skin is about a millimeter. So we're really, I mean, a millimeter is a tiny, tiny amount, maybe enough to get at like some of the cells that have to do with wrinkles and stuff. you know, but definitely not deeper than that. The infrared light can maybe get five millimeters beneath the skin, but you sure aren't getting through the skull with that kind of light. Like your brain is staying dark.

40:29Perry Wilson:So there's one kind of double blind placebo randomized controlled trial of evaluating people with traumatic brain injury. And, you know, broadly, it kind of shows nothing. They don't have any symptom improvement on the sort of standard measure of symptoms on this, which is a questionnaire. There's like some stuff in that paper saying that maybe when you put people in MRIs, like on one of the metrics that you measure in the MRI, maybe there's something statistically different. But again, we're in a space where we're looking at an awful lot of different outcomes and one of them is working. And that's kind of how statistics works, even if the results are zero.

41:10Perry Wilson:So the combination of lack of biological plausibility and lack of any real good evidence here, I think this feels like a real no-go on this.

41:23Emily Oster:It's a reach. When you've got a lot of placebo effects and issues with blinding and things like that, sometimes the animal literature can clue you in. We often see positive studies in animals that don't work in humans. That's a typical pathway. But this is one of those cases where actually the study in mice is negative. So there are mice that develop Alzheimer's disease or an Alzheimer's disease-like condition with the same sort of brain pathology that humans have. And they can test them by their ability to get through mazes and stuff like that. And they tried near-infrared 810 nanometer transcranial therapy three times a week for five months and the mice got no better at working through mazes or doing any of the problem solving tasks that mice are good to do um so we're here we're yeah i agree limited no essentially no

42:12Perry Wilson:biologic plausibility not for people and not for mice probably not strapping it to your head for that reason well what about perry okay so obviously on the internet uh there i think that that women get more of the wellness influencer push but the one thing that men are really really into is their hair. Men really don't like to lose their hair.

42:34Emily Oster:I can confirm that this is true.

42:36Perry Wilson:And so this comes up as like red light for hair loss. So should I put red light on my head for hair loss if I am a man or a woman, I guess, but men specifically?

42:44Emily Oster:I think I have good news and bad news here from my read of this research is that the good news is that red light therapy seems to be maybe as effective as minoxidil or finasteride, the two most common medications that we use for hair loss in terms of hair regrowth. The bad news is it seems to be as effective as minoxidil and finasteride for hair regrowth. Just to say, not very. We're not good at this. And this is something like, you don't care about wrinkles, you care about your running times. I care mildly about wrinkles, but boy, I would take like a thick, luscious head of hair. Like I, yes, I am into it.

43:29Emily Oster:And so this is where, this is where they twist the knife on me. So yes, there have been some studies which showed increased hair density with near infrared and deep red therapy about an increase in hair density of 41 hairs per centimeter squared. and I had to look into like how good that is. But again, that's similar to what you see for finasteride. There was actually, believe it or not, a randomized head-to-head comparison of minoxidil and red light therapy for hair regrowth. And there was no difference between them, which again, could be because neither of them work, but it could be because both of them work.

44:11Emily Oster:I mean, it will say that minoxidil and finasteride both are medications that have side effects. Minoxidil can lower your blood pressure, lead to a little bit of dizziness when standing up, things like that. Finasteride can have some sexual side effects reported and things like that. Whereas the adverse event rate for red light therapy is very low. So I'm not willing to write this one off completely. But even if I were really excited about this, I come to the same problem. And I think we've got to address this at the end. It's like, okay, sure. Let's even say, yeah, this works as well as finasteride and I might as well try it.

44:48Emily Oster:What do I do? What am I supposed to buy? Finasteride's a prescription.

44:53Perry Wilson:Yeah, this is the sort of core problem with this space, because in some ways, this is a very simple idea. Like we're going to put some wavelength of red-ish or red, more red, less red light onto something, your head, your face, your wounds, your something else. There is no like specific wavelength, specific criteria, specific dosing. Every one of these studies has a slightly different wavelength, a slightly different delivery mechanism, a slightly different dosing, a slightly different timeframe. It's all like really wild west. And so relative to some kind of medication where you'd say, okay, we're evaluating a medication.

45:31Perry Wilson:We have a dosing schedule. We have a dosing amount. You take the medication. We know exactly what the activity is you do to get the treatment effect. This is a place where even if you said, okay, you want to use it to grow your hair, we wouldn't really be able to give super specific information about what to do or what to buy or how to achieve?

45:50Emily Oster:I tried to keep like a running list of the parameters that these different things could have. And so there are different wavelengths. You mentioned that. There's different power density, right? Like how much wattage do you put into these bulbs, basically? There's different what they call fluence, which is the total energy delivered during a therapy session, right? So if you think like is more better, is less better. Some of these pulse at different frequencies. I've no idea if that makes a difference. And then there's the timing. Are you doing this every day? Are you doing it for 30 minutes, two hours, you know, just once a week, et cetera.

46:24Emily Oster:When you have a parameter space that big, it's nearly impossible to read any study. And unless you're using the exact same device that was used in that study, it's really hard to know that you're getting anything similar to what was actually studied. All right. This is stressing me out thinking of all the different possibilities for red light therapy. It's affecting my mood, but fortunately, I have something for you. Red light therapy. No, you don't. No, you don't.

46:51Perry Wilson:Okay. So I actually, I want to talk about mood because I think that the evidence on mood, the way that the impacts of the sort of idea that red light therapy might improve your mood, I think the way that literature has moved is actually a really interesting thing about science and almost a cautionary tale. So there's like one series of papers in a set of trials called the elated trials. And so what happened in these trials was there's like a pilot trial where they did a actually quite good, like double blind sham controlled study in which they tried to deliver red light therapy to people with major depressive disorder.

47:29Perry Wilson:And they found in this like small initial pilot that the effects on the subjects were much like the people who were treated were much more likely to be doing better than the people who were. So it looked like it had a very big effect. But when they like looked further into that particular study, they actually found that although they intended for the treatment to be blinded to the evaluating clinician, clinician, the evaluating clinicians like 80 % of the time were able to figure out what the treatment was. So like effectively they were, even though they had tried to blind, they were not blind.

48:04Perry Wilson:And so then they sort of took this as what it should be, which is like, this is an interesting suggestive hypothesis, but not conclusive with 20 subjects and this problem. And then they went to a much bigger study of like 50 people across multiple places and they did the same thing and they found nothing. And so it just turned out like in the better data, this does not seem to impact depression in this way. But I think it is a sort of, it's a good illustration of the kind of follow-up studies you'd want for other things in this space. If you thought, hey, this might work for this, let's do it in a larger setting where we're testing something much more specific, where we're doing much less p-hacking.

48:42Perry Wilson:That's kind of how science should work. It doesn't, often doesn't. Totally.

48:46Emily Oster:The power of replication is so huge.

48:49Perry Wilson:I mean, we do know that light affects mood, which is different from red light therapy affecting mood. I mean, I know because this winter is very depressing for many people.

48:57Emily Oster:Oh, yeah, yeah. For seasonal affective disorder, yes. Light box therapy has clearly been shown to improve mood.

49:04Perry Wilson:But it is not red. It's white.

49:05Emily Oster:It is not red. It's multi-spectrum, like the sun.

49:08Perry Wilson:Like the sun. So another thing that I see a lot is in the sports people is red light for muscle recovery. You know, I'm going to sit under a red light thing after my workout? Yes? No? Should I buy that? Probably yes, right? I should buy it. I'm going to buy it. I'm actually ordering it right now.

49:27Emily Oster:I mean, if I told you it would make your long run time faster, I know you're going to get your credit card out right now. So again, I think the depth of the tissue is the key biological plausibility indicator here. Again, even the infrared light therapy is only getting about five millimeters below the skin. So if you're talking about stuff that's deeper and five millimeters is a quarter of an inch, right? This is really not getting very deep. So if you're talking about any sort of deep tissue stuff, it's just not plausible that the light gets there. There are muscles on the surface and there are joints that are sort of in the surface.

50:05Emily Oster:Even that I think is probably too deep. I will say that if you look, you'll see some randomized trials in some athletes where they did see like, for example, one trial in 40 healthy subjects saw that they could do more reps after being given some of this red light therapy, as opposed to when they hadn't been given the red light therapy. You've pointed this out plenty of times. Reps is totally susceptible to placebo effect, right? You just believe in yourself and you can do more. I'm not very compelled by that. There's a nice negative trial, which looked at people doing eccentric bicep curls to exhaustion and compared a variety of different light sources.

50:50Emily Oster:And there's no difference across any of these groups. So it doesn't really make sense to me for exercise. It just doesn't get deep enough. That's basically the bottom line. There are, I think, a couple other things that we can just quickly knock out that I've seen online.

51:08Perry Wilson:Things we can reject.

51:09Emily Oster:Yeah, I think we just have to cross them off the list. So testosterone, no.

51:16Perry Wilson:Fat loss, no.

51:18Emily Oster:Although where are you shining the red light for the testosterone, that actually?

51:22Perry Wilson:That seems like a source of sunburn. I don't know. That feels like things could go very poorly.

51:27Emily Oster:We'll talk about that when we talk about safety.

51:30Perry Wilson:Fat loss is a no. This is not gonna give you better fat loss.

51:34Emily Oster:Yeah. Yeah. So taken all together before we move on to sort of the safety issues is like maybe for things that are very superficial. Basically, we're left with maybe some skin, maybe some hair.

51:46Perry Wilson:Maybe, but very, very small effects. I mean, I think we always want to think about, you know, is it likely that this is the like life changing, you know, is this the difference between a full, luscious head of hair and baldness? Is that the difference between looking like you're 60 and, you know, is this going to turn you into a 30 year old? no. Could there be some very marginal effect where when your partner squints at your face really, really carefully, maybe it looks a little bit different for them. Maybe. Also, why are they doing that? And so I think those are the, like, that for me, it's just like, like, maybe it's something there, but also it's definitely not something important.

52:26Emily Oster:Okay.

52:26Perry Wilson:So then there are two other, like, sort of downsides, I think, are worth talking about here. So one is the question of just like, is this safe? Like, let's say you're like, yeah, I hear you, Emily. But my partner does squint at my face a lot. And I really want to get these small improvements. Should I be concerned about safety? Yeah.

52:43Emily Oster:Again, one of the problems is there's a million of these devices online. And it can be really hard to know what to get. We can talk about that in a second. But one aspect of safety is just like these are electronic devices that may be manufactured in less than safe conditions. and things can spark and catch on fire and stuff like that. That's sort of the generic, like, don't buy these things from Timu, bit of warning. But biologically, there's some concern here too. Even in the Petri dish studies, they found what's called a biphasic response, depending on how much red light they put on these cells.

53:17Emily Oster:It seems like at the lower level, at kind of the right level, you increase ATP production and the cells kind of do their thing a little bit better. If you exceed that, you start to generate what are called reactive oxygen species. You're essentially like goosing your mitochondria too much. And it causes these inflammatory oxygen molecules to be created, which can actually kill the cells. So this is a mechanism that is one of the ways that light can actually hurt you. It can cause inflammation and things like that. And so there's this therapeutic window where there's the right amount and there's too much.

53:56Emily Oster:And we don't really know what that is. So I would say if you were going to use this, you probably don't want to like leave it on your face overnight or whatever you're doing. The second thing is, as you alluded to, is heat. So these things give off a lot of heat. In fact, one of the complaints I saw in some of the products online is that they're loud, which I didn't really realize, but they're loud because they have fans in them that are, you know, blowing off the heat from all the LEDs that are going through them. So they've got the fan blowing. That heat is potentially damaging, particularly if it's right up against your skin.

54:30Emily Oster:It's also one of the mechanisms that these things might work.

54:33Perry Wilson:It could be how it works. Yeah. Right.

54:35Emily Oster:We talk about muscle strain. It's like, oh yeah, the light doesn't get to your muscle, but it's warm.

54:39Perry Wilson:Like nice heating pad. Yeah. We have that. I have one.

54:42Emily Oster:It's a heating pad. Yeah, exactly. And it's a lot cheaper to get a heating pad, but, but too much heat can cause, can cause problems. And so generally these things are pretty safe, but, um, but there are some theoretical concerns that people should be aware of.

54:55Perry Wilson:I think the much bigger problem is these things are incredibly expensive. Oh my God. LED lights are cheap. Like, so if you just go to, you know, the home Depot and you get some LEDs like that's, that's nothing. Uh, but these masks are like, I mean, this stuff is really expensive. Thousands of dollars.

55:12Emily Oster:$1 ,500. And I tried to like, was like, how much could this possibly cost to make? And I know it's not just LEDs, which costs like a cent to maybe 50 cents each. But like, I know there's like some, probably some circuit boards and stuff in there, but there's no way these things cost$1 ,000 to make. I think these are all drastically inflated.

55:32Perry Wilson:It's called cost plus pricing. It's the cost plus the marketing budget. And that is most of it. Most of it is the marketing budget. So, I mean, I think there are some of these devices that are sort of FDA cleared, which I think makes people feel like they are more legitimate. That does not defend the pricing, though.

55:54Emily Oster:No, FDA clearance has nothing to do with pricing. But if people are, again, if you are looking for something, this is one way to distinguish one product from another. So an FDA cleared device is one that has gone through pre-marketing approval from the FDA. It's not that high a bar. They just have to prove that they're substantially similar to an already approved device. So it's called a predicate device. They have to show safety in some like manufacturing parameters. So at least you kind of know that like they went through a process. It's not a total scam. They also, if they are FDA cleared, then get the ability to make health claims, which are those, you know, you've seen it on non-FDA cleared devices, right?

56:41Emily Oster:This is not intended to diagnose, prevent, cure, or treat any disease. So devices that haven't gone through the FDA can't say that. So you'll see the non-FDA clear face mask that say like promotes, you know, facial wellness, facial wellness, but they can't say like we'll treat acne or like we'll treat rosacea. It doesn't mean they don't work per se, but that FDA clearance is something you could potentially look for, but it comes at a premium. Yeah.

57:11Perry Wilson:All right, Perry. Red light therapy. Smash or pass?

57:16Emily Oster:I am passing at the current price. I do think someone invents something to put on my scalp that costs like$100 and actually works. I might do it. How about you, Emily? Smash or pass?

57:34Perry Wilson:I'm a pass on this. I think that the effects are not big enough, And I think the likely actual effects, if you really got good ones, would be even more minuscule than the ones we estimate in the trials. And so I'm a pass. Save your money. Spend it on Botox if that's what you want. That's my feeling.

57:56Emily Oster:Roxanne, you don't have to put on the red light.

58:00Perry Wilson:You're really going to make that work. You're going to make it work. Sorry. That is it for Red Light Therapy, your mailbag question of the week after the break. When Kohler, the global design leader in luxurious kitchen and bath products, came to me and said, Martha, we need an ambassador for our timeless, elegant, durable cast iron products. I said, I'm in. Now let me see the factory. Weeks later, I was suited up in coveralls and work boots, walking through their Kohler, Wisconsin, cast iron foundry. I stood next to the molten iron furnace, saw the hand-applying enamel, and touched the gorgeous finished products waiting to be sent out into the world.

58:45Perry Wilson:Since 1883, Kohler cast iron products have been forged and finished by the incredible craftspeople right in Kohler, Wisconsin. I'll tell you, I gained a newfound respect and appreciation for Kohler's cast iron craftsmanship. So now, I'm lending my discerning stamp of approval to my most beloved Kohler cast iron products for their durability, beauty, and timelessness. Shop my Kohler cast iron favorites curated on Kohler.com. Bring the warmth, character, and enduring style of these timeless products into your kitchens and bathrooms. As the Kohler cast iron ambassador, I say, long live cast iron.

59:31Perry Wilson:When people turn to telehealth or weight loss, they're looking for real support. That's why more people are choosing orderlymeds.com. Orderly Meds connects you with real doctors and access to proven GLP-1 medications like semaglutide and terzeptatide. No guessing, just a more supportive experience. And all shipped directly to your door in discreet packaging. Do your research, ask questions, then visit orderlymeds.com slash podcast for an exclusive offer. That's orderlymeds.com slash podcast. Individual results may vary. Now medical advice, eligibility required. See site for details. Who doesn't love bread?

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1:01:22Perry Wilson:so you're not choosing between great taste and real benefits. You're getting both in every sip. Skypot Protein Soda. Reach for the sky. Get your Skypot Protein Soda now at Target. When your schedule sounds like this...

1:01:40Perry Wilson:Are you kidding me? An oil change is the last thing you have time for. So drive in to Take 5 and let our techs change your oil, check your tires, top off your fluids and have you back on the road pit stop fast. All while you stay in your car. No putting your entire schedule on hold. No upsells, no problem. So you can get back to your to-do list. Or not. Find your nearest shop at Take5.com. Take 5, the stay in your car 10-minute oil change. Hi, Emily and Perry. This is Adrienne from Minneapolis. And I have a question I always wanted to know the answer to. And that is the illusion or the reality of period sinking.

1:02:20Perry Wilson:I'm wondering if it's the kind of thing where like if I live with two female roommates and all of our periods seem to line up, is that a real thing with some kind of scientific basis? Or is it just like frequency illusion where we are all thinking about blue Volkswagen's and so we see them all the time?

1:02:40Emily Oster:Thanks for your help.

1:02:41Perry Wilson:Ah, this is an interesting question. People ask this a lot.

1:02:43Emily Oster:Before you get into it, do you know what the teenagers call this now? Oh, God. What do they call it? They call it getting Bluetoothed. Have you heard that?

1:02:51Perry Wilson:Oh, I did. Someone did tell me that. That's so weird. Like I'm going to Bluetooth you my period.

1:02:58Emily Oster:Yeah, because it's like you're connecting, you're syncing up, right? Like anyway, modern times.

1:03:03Perry Wilson:I don't know. How do you even know that?

1:03:05Emily Oster:I have a 16-year-old daughter.

1:03:07Perry Wilson:You have a 16-year-old daughter. Okay, fair enough. I think it's nice that you know that. But so there was some early research that suggested that people who live in a household together, I think it was based on dorms, would have periods at the same time. But then basically further, more detailed research shows that, in fact, this is not true. People do not sync their cycles. I mean, of course, if you have a dorm of 20 girls, many of them will have their period at the same time because your period is seven days, typically five to seven days out of a 28 day cycle. So you could easily feel synced because everyone has their period at the same time as some other person, but it is not like a, it's not a true syncing and that way your period is not moving around to match other people's.

1:03:57Perry Wilson:And I think it's not surprising because I don't know what the evolutionary reason for that would be. Like, why would it be beneficial for everybody to be fertile at the same time, that almost seems like the opposite of what you would want.

1:04:08Emily Oster:Right. Yeah. I don't know. I always hear like pheromones and stuff like that. There's an interesting mathematical correlate here, which is that in any system where there's periodicity, where there's things that are happening at recurring time points, but the periods are slightly different, they will sync over time and desync over time. So you see this if you're in traffic and you all have your left blinker turned on, right? And everyone's kind of blinking at slightly different rates because car manufacturers can't get it together. By the way, side note, car manufacturers, can we all blink at the same rate?

1:04:41Emily Oster:Okay. They all blink at different rates. If you kind of follow it, you'll see that they kind of are blinking and then they'll sort of sync up and you'll feel like, oh, we're all blinking and then it kind of desyncs again. So that's just a phenomenon of periodicity that could also be at play here. Right.

1:04:53Perry Wilson:Which would totally work here because of course, some people's cycles are - Yeah, a little bit different. Normal cycles can range from 21 to 35 days. So everybody's got a different blinker. That's totally fascinating. You knew a lot more about this than I thought that you would. I will say, I want to give you credit.

1:05:05Emily Oster:I am a man for all.

1:05:08Perry Wilson:Your renaissance, you're a renaissance man. That's all there is.

1:05:14Perry Wilson:All right. That's it for us for today. Stick with us next week and we'll ask, what's the deal with microplastics? Wellness Actually is produced in association with iHeart Media. Our senior producer is Tamar Avishai. Our executive producer at iHeart is Jennifer Bassett. Our theme music is by Eric Deutsch, and our content is for educational purposes only.

1:05:36Emily Oster:If you like the show, help other people find us. Leave a rating and review on Apple Podcasts or your podcatcher of choice and help us spread the word about the show. You can follow us on Instagram at wellnessactuallypod. And don't forget, we want to hear from you. Head over to wellnessactually.fm and leave us a question for our mailbag or suggest a topic for a future show.

1:05:58Perry Wilson:We'll let the influencers have the last word.

1:06:00Emily Oster:They make you wear eye goggles. Watch what happens to your vision after a week to 14 days of being in a red light therapy bed without eye protection. If you don't have a marked improvement in your vision, I'd be very surprised.

1:06:11Perry Wilson:So what is the negative aspect of why do they tell you to cover your eyes?

1:06:14Emily Oster:Well, because, you know, I guess the bright light, if you're staring directly at one of those lights, you got some kind of damage to your rods or your cones, your macular, your retina. I mean, if you had eye pathology, which you would know about, then there might be some downside consequences.

1:06:38Perry Wilson:When Kohler, global design leader in luxurious kitchen and bath products, asked me to be their ambassador for timeless, elegant, durable cast iron, I said, I'm in. Soon after, I was in their Kohler, Wisconsin foundry, watching molten iron poured, enamel applied by hand, and the beautiful finished pieces ready to ship. Since 1883, Kohler cast iron has been crafted by incredible artisans, and seeing it firsthand gave me a whole new appreciation for their craftsmanship. Now, I'm proud to lend my stamp of approval to my favorite Kohler cast iron products for their durability, beauty, and enduring style.

1:07:21Perry Wilson:Shop my curated picks at Kohler.com. As the Kohler cast iron ambassador, I say, long live cast iron. Less support through telehealth, but it feels overwhelming and rushed. Check out orderlymeds.com now. Orderlymeds.com was built to be different. Here, you connect with real doctors who take the time to understand your goals, review your eligibility, and guide you through a plan that's right for you. Orderly Meds provides access to proven GLP-1 medications like semaglutide and terzepatide, including both name brand options and personalized compound versions when appropriate. So you have choices backed by clinical oversight, not guesswork.

1:08:00Perry Wilson:It's a simpler, more supportive telehealth experience designed around people who want clarity, care, and confidence in their weight loss journey. And your medication is delivered directly to your home in discreet packaging. So your experience stays private from start to finish. Do your research. Ask the right questions. Then visit orderlymeds.com slash podcast for an exclusive offer. Again, that's orderlymeds.com slash podcast. Individual results may vary. Not medical advice. Eligibility required. See site for details. Who doesn't love bread? Satisfying sandwiches. Fully loaded bagels. Buttered rolls.

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