Using Light (Sunlight, Blue Light & Red Light) to Optimize Health | Huberman Lab Essentials

0:00 Welcome to Huberman Lab Essentials, where we revisit past episodes for the most

0:04 potent and actionable science-based tools for mental health,

0:08 physical health, and performance.

0:11 I'm Andrew Huberman and I'm a professor

0:13 of neurobiology and opthalmology at Stanford School of Medicine.

0:17 Today we are going to discuss light and the many

0:20 powerful uses of light to optimize our health.

0:23 One of the reasons why light has such powerful effects on so

0:26 many different aspects of our biology is that it can be translated

0:30 into electrical signals in our brain and body into hormone signals in our brain

0:35 and body and indeed into what we call cascades of biological pathways.

0:40 Meaning light can actually change the genes

0:43 that the cells of your bodies express.

0:45 And that is true throughout the lifespan.

0:47 Light is electromagnetic energy.

0:50 It can cause reactions in cells of your body.

0:53 It can cause reactions in fruit, for instance, right?

0:56 You see a piece of fruit and it's not ripe,

0:58 but it gets a lot of sunlight and it ripens.

1:00 That's because the electromagnetic energy of sunlight had an impact

1:05 on that plant or that tree or even on the fruit directly.

1:08 Now, the second thing that you need to understand about

1:10 the physics of light is that light has many different wavelengths.

1:14 And the simplest way to conceptualize this is to imagine

1:17 that cover of that Pink Floyd album where there's a prism.

1:19 You have a white beam of light going into that prism and then

1:22 the prism splits that beam of light into what looks like a rainbow.

1:26 So you got your reds, your orange, your greens, your blues, your purples, etc.

1:30 Now the third bullet point to understand about

1:32 the physics of light is that different wavelengths

1:35 of light because of the way that their wave

1:38 travels can penetrate tissues to different depths.

1:43 Every biological function of light has to do with the absorbance

1:48 or the reflectance of light or light passing through that particular thing,

1:53 meaning that particular cell or compartment within a cell.

1:57 I'd like to make it clear how this works by using the three primary

2:00 examples of how you take light

2:03 in your environment and convert it into biological events.

2:07 We have photo receptors in the back of our eyes.

2:10 These photo receptors come in two major types.

2:13 The so-called rods and the cones.

2:15 The rods are very elongated.

2:16 They look like rods.

2:17 And the cones look like little triangles.

2:20 The other place of course where light can impact

2:22 our body is on our surface on our skin.

2:25 In the top layer of skin which is called the epidermis.

2:28 We have caratinosytes and we have melanocytes.

2:32 With light exposure, those melanocytes will turn on genetic programs and other

2:38 biological programs that lead to enhanced pigmentation of the skin,

2:42 which we call tanning.

2:43 And the third example I'd like to provide is that of every cell of your body.

2:47 And what I mean by that is that every cell of your body,

2:50 meaning a cell that is part of your bone tissue

2:54 or your bone marrow or heart tissue or liver or spleen,

2:59 if light can access those cells,

3:01 it will change the way that those cells function for better or for worse.

3:05 For many organs within our body that reside deep to our skin,

3:11 light never arrives at those cells.

3:14 A really good example of this is the spleen.

3:17 Light will never land directly on your spleen,

3:20 but the spleen still responds to light information through indirect pathways.

3:26 Light arriving on the eyes is absorbed by a particular

3:32 cell type called the intrinsically photosensitive ganglen cell.

3:35 It's just a name.

3:36 You don't need to know the name,

3:37 but if you want, it's the so-called intrinsically photosensitive ganglen cell,

3:40 also called the melanopsin cell, because it contains an opsin,

3:43 a photo pigment that absorbs

3:46 shortwavelength light that arrives through sunlight.

3:50 Those cells communicate to particular stations in the brain

3:54 that in turn can connect to your so-called pineal gland,

3:58 which is this little P-sized gland in the middle

4:00 of your brain that releases a hormone called melatonin.

4:04 And the only thing you need to know

4:05 is that light activates these particular cells,

4:08 the intrinsically photosensitive melanopsin cells,

4:11 which in turn shuts down the production of melatonin from the pineal gland.

4:17 So melatonin is a transducer.

4:20 It's a communicator of how much light

4:22 on average is in your physical environment.

4:25 What this means is for people living in the northern hemisphere,

4:30 you're getting more melatonin release in the winter

4:32 months than you are in the summer months.

4:35 So you have a calendar system that is based in a hormone and that hormone

4:42 is using light in order to determine where

4:45 you are in that journey around the sun.

4:48 Now this is beautiful.

4:49 At least to me, it's beautiful because what it means is that the environment

4:53 around us is converted into a signal that changes the environment within us.

4:58 That signal is melatonin.

5:00 And melatonin is well known for its role in making

5:03 us sleepy each night and allowing us to fall asleep.

5:06 Many of you have probably heard before,

5:08 I am not a big fan of melatonin supplementation for a number of reasons,

5:11 but just as a quick aside, the levels of melatonin that are in most supplements

5:15 are far too high to really be considered physiological.

5:18 They are indeed super physiological in most cases.

5:21 And melatonin can have a number of different effects, not just related to sleep.

5:26 But that's supplemented melatonin.

5:28 Here I'm talking about our natural production and release of melatonin

5:32 according to where we are in the 365day calendar year.

5:37 Indogenous melatonin,

5:38 meaning the melatonin that we make within our bodies naturally,

5:40 not melatonin that's supplemented, has two general categories of of effects.

5:46 The first set of effects are so-called

5:48 regulatory effects and the others are protective effects.

5:50 The regulatory effects are for instance

5:52 that melatonin can positively impact bone mass.

5:57 Melatonin is also involved in maturation of the gonads during puberty,

6:01 the ovaries and the testes.

6:03 Although there the effects of melatonin tend to be

6:05 suppressive on maturation of the ovaries and testes.

6:09 meaning high levels of melatonin tend to reduce

6:12 testicle volume and reduce certain functions within the testes

6:17 including sperm production and testosterone production and within

6:20 the ovaries melatonin can suppress the maturation of eggs etc.

6:24 Now, I don't want anyone to get scared if you've been taking melatonin.

6:27 Most of the effects of melatonin on those functions are reversible.

6:31 But I should point out that one

6:33 of the reasons why children don't go into puberty

6:35 until a particular age is that young

6:38 children tend to have chronically high indogenous melatonin,

6:41 and that is healthy to keep them out of puberty

6:43 until it's the right time for puberty to happen.

6:47 I should also mention that melatonin

6:48 is a powerful modulator of placental development.

6:51 So for anyone that's pregnant,

6:53 if you're considering melatonin supplementation, please, please,

6:56 please talk to your OB/GYN, talk to your other doctor as well,

7:00 you want to be very,

7:01 very cautious because of the powerful effects that melatonin

7:04 can have on the developing fetus and placenta.

7:06 So when we think about light impacting our biology,

7:10 the reason I bring up melatonin as the primary example of that is

7:13 a because melatonin impacts so many

7:15 important functions within our brain and body,

7:17 but also because hormones in general, not always,

7:20 but in general are responsible for these slow modulatory effects on our biology.

7:25 And so I'm using this as an example of how light

7:28 throughout the year is changing the way that your the different

7:31 cells and tissues and organs of your body are

7:33 working and that melatonin is the transducer of that signal.

7:37 So in order to get light information to the pineal and thereby

7:42 get the proper levels of melatonin according to the time of year,

7:47 we should all try and get outside as much

7:49 as possible during the long days of summer and spring.

7:53 And in the winter months, it makes sense to spend more time indoors.

7:57 For those of you that suffer from seasonal effective disorder,

7:59 which is a seasonal depression,

8:01 or feel low during the fall and winter months, there are ways to offset this.

8:04 We did an entire episode on mood and circadian rhythms where we describe this.

8:08 So, it does make sense for some people to get more bright light in their eyes

8:11 early in the morning and throughout the day during the winter months as well.

8:15 But nonetheless, changes in melatonin,

8:19 meaning changes in the duration of melatonin

8:21 release across the year are normal and healthy.

8:23 So provided that you're not suffering from depression,

8:26 it's going to be healthy to somewhat modulate

8:28 your amount of indoor and outdoor time across the year.

8:31 The other thing to understand is the very firmly established fact,

8:33 which is that light powerfully inhibits melatonin.

8:37 If you wake up in the middle of the night and you go into the bathroom

8:40 and you flip on the lights

8:42 and those are very bright overhead fluorescent lights, your melatonin levels,

8:46 which would ordinarily be quite high in the middle

8:49 of the night because you've been eyes closed in the dark presumably,

8:52 will immediately plummet to near zero or zero.

8:55 If you do that every once in a while, it's not going to be a problem.

8:58 But if you're doing that night after night,

9:00 you are really disrupting this fundamental signal

9:05 that occurs every night regardless of winter, spring, summer, etc.

9:08 And that is communicating information about where

9:11 your brain and body should be in time.

9:14 In animals such as mice, but also in humans,

9:18 exposure to light, in particular, UV blue light, so short wavelengths of light,

9:24 can trigger increases in testosterone and estrogen and the desire to mate.

9:29 But it is not the exposure of light to the eyes.

9:32 It turns out that it is the exposure of your skin to particular

9:36 wavelengths of light that is triggering

9:39 increases in the hormones testosterone and estrogen.

9:42 I think the results are best understood

9:44 by simply going through the primary data,

9:47 meaning the actual research on this topic.

9:49 And to do so, I'm going to review

9:50 a paper that was published in the journal cell reports,

9:53 cell press journal, excellent journal,

9:55 entitled skin exposure to UVB light induces

9:59 a skin brain gonad axis and sexual behavior.

10:03 And I want to emphasize that this was a paper that focused on mice

10:08 in order to address specific mechanisms because

10:10 in mice you can so-called knock out particular genes.

10:14 You can remove particular genes to understand mechanism.

10:16 You just can't do that in humans in any kind

10:18 of controlled way at least not at this point in time.

10:22 And this study also explores humans and looked

10:25 at human subjects both men and women.

10:28 The basic finding of this study was

10:30 that when mice or humans were exposed to UVB, meaning ultraviolet blue light,

10:36 so short wavelength light of the sort that comes through in sunshine,

10:40 but is also available through various artificial sources.

10:44 If they received enough exposure of that light to their skin,

10:50 there were increases in testosterone that were

10:53 observed within a very brief period of time.

10:56 also increases in the hormone estrogen.

10:59 And I should point out that the proper ratios

11:01 of estrogen and testosterone were maintained in both males and females,

11:04 at least as far as these data indicate.

11:07 And mice tended to seek out mating more and mate more.

11:12 There were also increases in gonatal weight,

11:15 literally increases in testes size and in ovarian size when

11:19 mice were exposed to this UVB light past a certain threshold.

11:23 They did not look at testes size or ovarian size in the human subjects.

11:28 However, because they are humans,

11:30 they did address the psychology of these human beings

11:34 and address whether or not they had increases in, for instance,

11:37 aggressiveness or in passionate feelings and how

11:40 their perception of other people changed

11:44 when they were getting a lot of UVB light exposure to the skin.

11:48 UVB light exposure also changed various aspects of female

11:52 biology related to fertility in particular follicle growth.

11:56 Follicle and egg maturation are well-known indices

12:01 of fertility and of course correlate with the menstrual

12:04 cycle in adult humans and is related

12:07 overall to the propensity to become pregnant.

12:10 UVB light exposure enhanced maturation of the follicle which

12:14 just meant that more healthy eggs were being produced.

12:17 So in terms of thinking about a protocol to increase testosterone and estrogen,

12:21 mood and feelings of passion, the idea is that you would want to get

12:26 this two to three exposures per week minimum of 20

12:31 to 30 minutes of sunlight exposure onto as much

12:34 of your body as you can reasonably expose it to.

12:38 Another set of very impressive effects of UVB light,

12:40 whether or not it comes from sunlight or from an artificial source,

12:44 is the effect of UVB light on our tolerance for pain.

12:47 It turns out that our tolerance for pain varies across the year

12:51 and that our pain tolerance is increased in longer day conditions.

12:56 This is occurring via UVB exposure to the skin and UVB exposure to the eyes.

13:03 I want to just describe two studies

13:04 that really capture the essence of these results.

13:07 The first study is entitled skin exposure to ultraviolet

13:10 B rapidly activate systemic neuroendocrine and immunosuppressive responses.

13:15 Basically what they observed is that even one exposure to UVB light

13:20 change the output of particular hormones and neurochemicals in the body such

13:24 as corticotropen hormone and betaendorphins which

13:28 are these endogenous opioids in order

13:30 to counter pain and act as a somewhat of a psychological soother also.

13:36 What they found was that exposure to UVB

13:39 light increased the release of these beta endorphins.

13:42 Now a second study published in the journal

13:44 Neuron cell press journal excellent journal is entitled

13:48 a visual circuit related to the perryqueductal gray

13:50 area for the anti-nosceptive effects of bright light treatment.

13:54 I'll translate a little bit of that for you.

13:57 The perryqueductal gray is a region of the midbrain

14:00 that contains a lot of neurons that can release indogenous opioids.

14:06 things like beta eneopioid.

14:11 These are all names of chemicals that your body can manufacture

14:14 that act as endogenous painkillers and increase your tolerance for pain.

14:18 They actually make you feel less pain overall

14:21 by shutting down some of the neurons that perceive pain.

14:24 They're not going to block the pain response so

14:26 that you burn yourself unnecessarily or harm yourself unnecessarily,

14:29 but they act as a bit of a painkiller from the inside.

14:33 The key finding of this study is that it is

14:35 light landing on the eyes is captured by these melanopsin cells.

14:41 They absorb that light, translate that light into electrical signals that are

14:45 handed off to areas of the brain to evoke

14:47 the release of these indogenous opioids that soothe

14:50 you and lead to less perception of pain.

14:53 So for those of you that are thinking tools and protocols,

14:56 try to get some UVB exposure, ideally from sunlight.

15:00 I think the 20 to 30 minute protocol two

15:02 or three times per week is an excellent one.

15:04 Even on a cloud covered day, you are going to get far more light energy,

15:10 photons through cloud cover than you are

15:14 going to get from an indoor light source, an artificial light source.

15:17 If you see some sunlight throughout the day,

15:19 you would do yourself a great favor to try

15:22 and chase some of that sunlight and get into that sunlight.

15:25 Never ever look at any light, artificial sunlight or otherwise,

15:28 that's so bright that it's painful to look at.

15:30 It's fine to get that light arriving on your eyes indirectly.

15:34 It's fine to wear eyeglasses or contact lenses.

15:36 In fact, if you think about the biology

15:38 of the eye and the way that those lenses work,

15:40 they will just serve to focus that light onto the very

15:43 cells that you want those light beams to be delivered to.

15:47 Whereas sunglasses that are highly reflective

15:49 or trying to get your sunlight exposure

15:51 through a windshield of a car or through a window simply won't work.

15:55 Most windows are designed to filter out the UVB light.

15:59 And if you're somebody who's really keen on blue

16:02 blockers and you're wearing your blue blockers all day,

16:04 well, don't wear them outside.

16:06 And in fact, you're probably doing yourself a disservice

16:09 by wearing them in the morning and in the daytime.

16:11 There certainly is a place for blue blockers in the evening

16:14 and nighttime if you're having issues with falling and staying asleep.

16:17 But if you think about it, blue blockers,

16:19 what they're really doing is blocking those short wavelength UVB wavelengths

16:23 of light that you so desperately need to arrive at your retina

16:27 and of course also onto your skin in order to get

16:30 these powerful biological effects on hormones and on pain reduction.

16:34 These data also might make you think a little bit about

16:37 whether or not you should wear short sleeves or long sleeves,

16:39 whether or not you want to wear shorts or a skirt or pants.

16:42 But you might take into consideration that it

16:44 is the total amount of skin exposure that is going to allow you to capture

16:48 more or fewer photons depending on, for instance,

16:52 if you're completely cloaked in clothing and you're just,

16:55 you know, exposed in the hands, uh, neck and face such as I am now,

16:59 or whether or not you're outside in shorts and a t-shirt,

17:01 you're going to get very, very different patterns of biological

17:06 signaling activation in those two circumstances.

17:08 Many of you, I'm guessing, are wondering whether or not you should seek out UVB

17:13 exposure throughout the entire year or only in the summer months.

17:16 And that's sort of going to depend on whether

17:18 or not you experience depression in the winter months,

17:23 so-called seasonal effective disorder.

17:25 Some people have mild,

17:26 some people have severe forms of seasonal effective disorder.

17:28 Some people love the fall and winter and the shorter days.

17:31 Really, it has to be considered on a case- by case basis.

17:34 I personally believe,

17:35 and this was reinforced by the director of the chronobiology

17:40 unit at the National Institutes of Mental Health, Samaritar,

17:42 that we would all do well to get

17:44 more UVB exposure from sunlight throughout the entire year,

17:48 provided we aren't burning our skin or damaging our eyes in some way.

17:53 In addition to that, during the winter months,

17:55 if you do experience some drop in energy

17:59 or increase in depression or psychological lows,

18:04 it can be very beneficial to access a sad lamp or if you don't

18:09 want to buy a sad lamp because often times they can be very expensive.

18:12 You might do well to simply get a LED lighting panel.

18:16 Very inexpensive compared to the typical SAD lamp.

18:18 I actually have one and I position on my desk all day long.

18:20 I also happen to have skylights above my desk.

18:23 I'm fairly sensitive to the effects of light, so in longer days,

18:26 I feel much better than I do in shorter days.

18:27 I've never suffered from full-blown seasonal effective disorder,

18:30 but I keep that light source on throughout the day throughout the year.

18:34 But I also make it a point to get outside and get

18:36 sunlight early in the morning and several times throughout the day.

18:39 People that are blind, provided they still have eyes,

18:42 often maintain these melanopsin cells.

18:45 So even if you're low vision or no vision,

18:47 getting UVB exposure to your eyes can be very beneficial for sake of mood,

18:52 hormone pathways, pain reduction and so forth.

18:55 A cautionary note, people who have retinitis pigmentotosa,

19:00 macular degeneration or glaucoma, as well as people who are especially prone

19:04 to skin cancers should definitely consult with your opthalmologist

19:08 and dermatologist before you start increasing the total amount

19:11 of UVB exposure that you're getting from any source, sunlight or otherwise.

19:16 There are additional very interesting and powerful effects

19:18 of UVB light in particular on immune function.

19:23 All the organs of our body are inside our skin.

19:26 And so information about external conditions,

19:29 meaning the environment that we're in, need to be

19:32 communicated to the various organs of your body, such as your spleen,

19:35 which is involved in the creation of molecules and cells that combat infection.

19:40 There are beautiful studies showing that if we get

19:43 more UVB exposure from sunlight or from appropriate artificial sources

19:50 that spleen and immune function are enhanced and there's

19:55 a very logical wellestablished circuit as to how that happens.

19:58 Your brain actually connects to your spleen.

20:02 UVB light arriving on the eyes is known to trigger

20:05 activation of the neurons within the so-called sympathetic nervous system.

20:09 These neurons are part of the larger

20:12 thing that we call the autonomic nervous system,

20:14 meaning it's below or not accessible by conscious control.

20:18 It's the thing that controls your heartbeat, controls your breathing,

20:20 and that also activates or flips on the switch of your immune system.

20:24 When we get a lot of UVB light in our eyes

20:27 or I should say sufficient UVB light in our eyes, a particular channel,

20:32 a particular set of connections within

20:34 the sympathetic nervous system is activated and our spleen deploys immune cells

20:40 and molecules that scavenge for and combat infection.

20:43 In other words, the soldiers of your immune system,

20:45 the chemicals and cell types of your immune system that combat

20:49 infection are in a more ready deployed stance, if you will.

20:54 So, we often think about the summer months

20:56 and the spring months as fewer infections floating around,

21:00 but in fact, there aren't fewer infections floating around.

21:03 We are simply better at combating those infections

21:06 and therefore there's less infection floating around.

21:09 What does this mean in terms of a tool?

21:11 What it means is that during the winter months,

21:13 we should be especially conscious of accessing UVB light to enhance

21:19 our spleen function to make sure

21:22 that our sympathetic nervous system is activated

21:24 to a sufficient level to keep our immune system deploying all those killer

21:28 T- cells and B cells and cytoines so that when we encounter the infections,

21:32 as we inevitably will, we can combat those infections well.

21:36 And as just a brief aside, but I should mention a brief aside that's

21:40 related to tens of thousands of quality studies.

21:43 It is well known that wound healing is

21:45 faster when we are getting sufficient UVB exposure.

21:49 It is known that turnover of hair cells.

21:53 The very cells that give rise to hair cells are called stem cells.

21:56 They live in little so-called niches in our skin with these hair

21:59 stem cells and your hair grows faster in longer days.

22:02 That too is triggered by UVB exposure.

22:06 not just to the skin but to the eyes.

22:09 That's right.

22:10 There was a study published in the proceedings

22:12 of the National Academy of Sciences

22:14 a couple of years ago that showed that the exposure of those melanops

22:18 and ganglin cells in your eyes is

22:20 absolutely critical for triggering the turnover of stem

22:24 cells in both the skin and hair and also it turns out in nails.

22:30 So, if you've noticed that your skin, your hair,

22:32 and your nails look better and turn over more,

22:35 meaning grow faster in longer days, that is not a coincidence.

22:39 That is not just your perception.

22:41 In fact, hair grows more.

22:44 Skin turns over more, meaning it's going to look more youthful.

22:46 You're going to essentially remove older skin

22:49 cells and replace them with new cells.

22:52 and all the renewing cells and tissues

22:54 of our body are going to proliferate are going

22:56 to recreate themselves more when we're getting sufficient UVB

23:00 light to our eyes and also to our skin.

23:03 There's also another time of day or rather I should

23:06 say a time of night in which UVB can be

23:09 leveraged in order to improve mood but it's actually

23:13 the inverse of everything we've been talking about up until now.

23:17 We have a particular neural circuit that originates with those melanopsin cells

23:21 in our eye that bypass all the areas

23:24 of the brain associated with circadian clocks.

23:27 So everything related to sleep and wakefulness that's specifically

23:31 dedicated to the pathways involving the release of molecules like

23:34 dopamine and other molecules as well including serotonin and some

23:37 of those indogenous opioids that we talked about before.

23:40 That particular pathway involves a brain

23:42 structure called the perihabenular nucleus.

23:44 The perihabenular nucleus gets input from the cells in the eye

23:49 that respond to UVB light and frankly to bright

23:53 light of other wavelengths as well because as you recall

23:55 if a light is bright enough even if it's not UV

23:58 or blue light it can activate those cells in the eye

24:01 those cells in the eye communicate to the perihabenular nucleus

24:05 and as it turns out if this pathway is activated

24:09 at the wrong time of each 24-hour cycle mood gets worse.

24:15 Dopamine output gets worse.

24:18 Molecules that are there specifically to make us

24:20 feel good actually are reduced in their output.

24:24 Avoiding UVB light at night is actually a way in which we can

24:30 prevent activation of this eye to perihabular

24:34 pathway that can actually turn on depression.

24:37 to be very direct and succinct about this.

24:39 Avoid exposure to UVB light from artificial sources between the hours of 10 p.m.

24:44 and 4:00 a.m.

24:45 If you view UVB light, you activate those neurons in your eye very potently.

24:50 And if those cells communicate to the perihabular nucleus, which they do,

24:54 you will truncate or reduce the amount of dopamine that you release.

24:59 So if you want to keep your mood elevated,

25:02 get a lot of light, UVB light throughout the day.

25:05 And at night, really be cautious

25:07 about getting UVB exposure from artificial sources.

25:10 Now, I wouldn't want people to become so neurotic about

25:13 UVB exposure that they won't flip on a light at all.

25:16 But you would do well, for instance,

25:18 to put any artificial lights that you have on in the evening,

25:21 kind of low in your physical environment.

25:23 Because these melanopsin cells reside in the lower half of our eyes,

25:26 they view the upper visual field.

25:27 That makes sense because they were designed

25:29 to essentially respond to sunlight coming from above

25:32 us and try and dim those lights as far down as you safely can.

25:37 Now, I'd like to shift our attention to the other end of the spectrum,

25:40 meaning the light spectrum, to talk about red light and infrared light,

25:43 which is long wavelength light.

25:45 So, you're probably asking, or at least you should be asking,

25:47 how is it that shining red light on our skin

25:50 can impact things like acne and wound healing, etc.

25:53 To understand that, we have to think back to the beginning

25:55 of the episode where I described how longwavelength light such

25:59 as red light and near infrared light which is even longer

26:02 than red light can pass through certain surfaces including our skin.

26:07 So our skin has an epidermis which is on the outside

26:10 and the dermis which is in the deeper layers.

26:12 Red light and infrared light can pass down into the deeper layers

26:16 of our skin where it can change the metabolic function of particular cells.

26:21 So let's just take acne as an example.

26:24 Within the dermis, the deep layers of our skin,

26:26 we have what are called sebaceous glands that actually

26:28 make the oil that is present in our skin.

26:32 Those sebaceous glands are often nearby hair follicles.

26:35 So if you've ever had a infected hair follicle,

26:38 that's not a coincidence that hair follicles tend to get infected.

26:41 Part of it is because there's actually

26:43 a portal down and around the hair follicle.

26:45 But the sebaceous gland is where the oil is created

26:48 that is going to give rise to for instance acne lesions.

26:52 Also in the dermis in the deep layers of the skin are the melanocytes.

26:56 They're not just in the epidermis.

26:57 They're also in the deeper layers of the skin.

27:00 And you have the stem cells that give rise to additional skin cells.

27:05 If the top layers of the epidermis are damaged,

27:07 those stem cells can become activated.

27:09 And you also have the stem cells that give rise to hair follicles.

27:13 What happens is the top layers of the skin are basically burned off

27:18 by a very low level of burn andor the cells in the deeper

27:22 layer start to churn out new cells which go and rescue the lesion

27:27 essentially clear out the lesion and replace

27:29 that lesion with healthy skin cells.

27:33 This does work in the context of wound healing getting scars to disappear.

27:38 It also works to remove certain patches of pigmentation.

27:42 Long wavelength light can actually get deep into the skin.

27:46 I mentioned that before,

27:47 but can also get into individual cells and can access the so-called organels.

27:52 In particular, they can access the mitochondria

27:54 which are responsible for producing ATP.

27:57 As cells age, and in particular in very metabolically active cells,

28:03 they accumulate what are called ROS's, reactive oxygen species.

28:08 And as reactive oxygen species go up,

28:12 ATP energy production in those cells tends to go down.

28:15 It's a general statement,

28:16 but it's a general statement that in most cases is true.

28:19 So the way to think about this is that red

28:21 light passes into the deeper layers of the skin, activates mitochondria,

28:25 which increases ATP and directly

28:28 or indirectly reduces these reactive oxygen species.

28:31 These reactive oxygen species are not good.

28:34 We don't want them.

28:35 They cause cellar damage, cellar death,

28:38 and for the most part just inhibit the way that our cells work.

28:42 So, if you've heard of red light

28:44 or near infrared light therapies designed to heal

28:48 skin or improve skin quality or remove lesions

28:50 or get rid of scars or unwanted pigmentation.

28:54 That is not pseudocience.

28:56 That is not woo science.

28:58 That is grounded in the very biology of how

29:00 light interacts with mitochondria and reactive oxygen species.

29:03 The key point here is that light is activating

29:06 particular pathways in cells that can either drive death

29:10 of cells or can make those cells essentially younger

29:14 by increasing ATP by way of improving mitochondrial function.

29:19 And in recent years, there have been some just beautiful examples that exist

29:23 not only in the realm of skin biology, but in the realm of neurobiology,

29:28 whereby red light and near infrared light can actually

29:31 be used to enhance the function of the cells

29:34 that for instance allow us to see better

29:36 and indeed cells that allow us to think better.

29:39 And these are the data from Dr.

29:41 Glenn Jeffrey at University College London who again is a long-standing

29:46 member of the neuroscience community working on visual neuroscience and who over

29:50 the last decade or so has really emphasized the exploration of red

29:54 light and near infrared light for restoration of neuronal function as we age.

30:00 The Jeffrey Lab has published two studies in recent years on humans that looked

30:06 directly at how red light and near infrared light can improve visual function.

30:11 The Jeffrey Lab approached these studies with that understanding

30:14 of how mitochondria and reactive oxygen species and ATP work.

30:18 And what they did is they had people, subjects that were either younger,

30:22 so in their 20s, or 40 years old or older,

30:27 view red light of about 670 nanometers.

30:30 670 nanometers would appear red to you and me.

30:33 They had they had them do that, excuse me,

30:36 at a distance that was safe for their eyes.

30:38 So at about a foot away.

30:40 And they had them do that anywhere from 2 to 3 minutes per day.

30:44 And in one study they had them do

30:45 that for a long period of time of about 12 weeks.

30:48 And in the other study they had them do that just for a couple of weeks.

30:51 The major findings were that in individuals 40 years old or older,

30:57 so in the 40 to 72 year old bracket,

31:01 but not in the subjects younger than 40 years old.

31:05 They saw an improvement in visual function.

31:08 That improvement in visual function was an improvement

31:11 in visual acuity meaning the ability to resolve fine detail

31:15 and using a particular measure of visual function which is

31:19 called the Triton exam tr I tan Triton exam which

31:26 specifically addresses the function of the so-called shortwavelength cones

31:31 the ones that respond to green and blue light they

31:34 saw a 22% improvement in visual acuity which

31:38 in the landscape of visual testing is an extremely exciting result.

31:44 As we age, we tend to lose rods.

31:46 We tend to lose other cells within the retina,

31:48 including the cells that connect the eye to the brain,

31:50 the so-called ganglen cells.

31:52 However, because rods and cones,

31:55 both are not just among the most metabolically active cells in your entire body,

32:00 but the most metabolically active cells in your entire body.

32:04 Those cells tend to accumulate a lot of reactive oxygen species as we age.

32:10 Red light of the sort used in these studies

32:12 was able to reduce the amount of reactive oxygen species in the rods and cones

32:18 and to rescue the function of this particular cone type,

32:22 the short wavelength and medium wavelength cones.

32:23 The important takeaway here is that viewing red light

32:26 and near infrared light at a distance at which it

32:29 is safe for just a couple of minutes each day

32:32 allowed a reversal of the aging process of these neurons.

32:36 So here we're seeing a reversal of the aging

32:38 process in neurons by shining red light on those neurons.

32:42 So a little bit more about the studies from the Jeffrey lab.

32:47 One of the things that they observed was a reduction in so-called dusen duen.

32:52 Dusen are little fatty deposits,

32:56 little cholesterol deposits that accumulate in the eye as we age.

33:00 Our neural retina being so metabolically active requires a lot of blood flow.

33:04 It's heavily vascularized and dusen are a special

33:08 form of cholesterol that accumulate in the eye.

33:10 As it turns out, these red light

33:12 and near infrared light therapies explored by the Jeffrey

33:15 lab were able to actually reduce or reverse some of the accumulation of dusen.

33:21 And so in addition to reducing reactive oxygen species,

33:25 the idea in mind now is that red light may actually reduce

33:29 cholesterol deposits and reactive oxygen species

33:33 in order to improve neuronal function.

33:35 So what should you and I do with these results

33:37 or should we do anything with these results?

33:39 Well, first of all, I want to emphasize

33:41 that even though these studies are very exciting,

33:43 they are fairly recent and so more data as always are needed.

33:47 There's some additional features of these studies

33:49 that I think are also important to consider.

33:51 First of all, the exposure to red light needed to happen early in the day,

33:56 at least within the first 3 hours of waking.

34:00 How would one do that?

34:01 Well, nowadays there are a number of different

34:03 red light panels and different red light sources

34:07 that certainly fall within the range of red

34:09 light and near infrared light that one could use.

34:12 So, if you're somebody who wants to explore red light therapy,

34:15 here's what you need to do.

34:16 You need to make sure that that red light source,

34:19 it's not so bright that you're damaging your eye.

34:21 A good rule of thumb is that something isn't painful to look at.

34:25 And in fact, I should just emphasize that anytime you look at any light source,

34:28 sunlight or otherwise,

34:29 that it's painful and makes you want to squint or close your eyes,

34:32 that means it's too bright to look at without closing your eyes.

34:35 Okay, that's sort of a duh, but I would loathe to think that anyone

34:38 would harm themselves with bright light in any way.

34:40 I don't just say that to protect us.

34:42 I say that to protect you, of course,

34:44 because you are responsible for your health.

34:45 And again, retinal neurons do not regenerate.

34:48 Once they are gone and dead, they do not come back.

34:51 The wavelength of light is important.

34:53 It is red light and near infrared light

34:55 that is going to be effective in this scenario.

34:58 The authors of this study emphasized that it was

35:00 red light of 670 nanometers in wavelength and near

35:04 infrared light of 790 nanometers in wavelength that were

35:10 effective and that those wavelengths could be complimentary.

35:13 A lot of the commercially available red light panels that you'll

35:15 find out there combine both red light and near infrared light.

35:19 However, I want to emphasize that most of the panels that are commercially

35:22 available are going to be too bright to safely look at very close up.

35:28 And in fact, that's why most of those red

35:30 light panels are designed for illumination of the skin

35:32 and oftentimes arrive in their packaging with eye protectors

35:36 that are actually designed to shield out all the red light.

35:39 So take the potential dangers of excessive illumination

35:44 of the eyes with any wavelength of light seriously.

35:47 But if you're going to explore 670 and 790

35:49 nanometer light for sake of enhancing neuronal function,

35:54 set it at a distance that's comfortable to look

35:56 at and that doesn't force you to squint or doesn't make you

35:58 feel uncomfortable physically as if you need to turn away during

36:03 the period of that two to three minute illumination each day.

36:06 So the studies I just described once again involve the use of red light early

36:11 in the day within three hours of waking

36:13 and are for the sake of improving neuronal function.

36:15 Red light has also been shown to be beneficial late

36:19 in the day and even in the middle of the night.

36:22 And when I say middle of the night,

36:24 I'm referring to studies that explored the use of red light for shift workers.

36:28 I realize that many people are doing shift work

36:30 or they have to work certainly past 10 p.m.

36:32 or maybe they're taking care of young children in the middle

36:35 of the night and they have to be up.

36:37 In that case, red light can actually be very beneficial.

36:39 And nowadays, there are a lot of sources

36:40 of red light available just as red light bulbs.

36:43 You don't need a panel.

36:45 So, what I'm basically saying is that it

36:47 can be beneficial to use red lights at night.

36:50 The study I'd like to emphasize in this context is entitled red light,

36:54 a novel non-farmacological intervention to promote alertness in shift workers.

36:59 The takeaway from this study is very clear.

37:01 If you need to be awake late at night for sake

37:04 of shift work or studying or taking care of children, etc.,

37:07 Red light is going to be your best

37:09 choice because if the red light is sufficiently dim,

37:15 it's not going to inhibit melatonin production

37:17 and it's not going to increase cortisol at night.

37:21 Cortisol should be high early in the day or at least should

37:24 be elevated relative to other times of day if you are healthy.

37:27 A late shifted increase in cortisol, however, 9M cortisol, 10 p.m.

37:31 cortisol is well known to be associated

37:33 with depression and other aspects of mental health, rash, as a mental illness.

37:38 So, if you do need to be awake at night or even all night,

37:42 red light is going to be the preferred light source.

37:46 And in terms of how bright to make it, well,

37:48 as dim as you can while still being able

37:51 to perform the activities that you need to perform.

37:53 That's going to be your best guide.

37:54 Today I covered what I would say is a lot of information.

37:58 My goal was to give you an understanding of how

38:01 light can be used to change the activities of cells,

38:05 organels within those cells, entire organs,

38:08 and how that can happen locally and systemically.

38:12 So, thank you once again for joining me

38:14 today for this deep dive discussion into phototherapies,

38:17 meaning the power of light to modulate our biology and health.

38:21 And as always, thank you for your interest in science.