Latest / So That's Why / Why Does Hair Turn Grey?

Transcript

Why Does Hair Turn Grey? · So That's Why

• 0:04
  Jen Oliver: welcome to the, so that's Why podcast, where we unpack the
• 0:08
  science behind everyday questions.
• 0:10
  I'm Jen.
• 0:11
  Chris Smith: I'm Chris.
• 0:12
  Jamie Eynon: And I'm Jamie.
• 0:13
  Jen Oliver: Okay, so hands up if you've ever pulled out a single strand of hair.
• 0:19
  Held it up to the light and thought, when did that happen?
• 0:23
  Why does our hair turn grey?
• 0:26
  Because it's one of the most visible changes our bodies go through, and
• 0:29
  yet most of us have no idea what's actually going on beneath the surface.
• 0:35
  Jamie Eynon: It
• 0:35
  really is.
• 0:36
  And can we talk about the universal panic of finding your first grey hair?
• 0:40
  You spot one in the mirror and suddenly you're doing a full scalp inspection
• 0:44
  like you're searching for contraband.
• 0:47
  Then you are texting your mates asking when they started trying
• 0:50
  to work out if you are ahead of schedule or behind schedule.
• 0:53
  Jen Oliver: I remember my first grey hair.
• 0:55
  I was convinced it was just a trick of the light, and so I actually moved to
• 0:58
  about three different mirrors before I accepted that it was well and truly white.
• 1:03
  Chris Smith: And here's something that might surprise you, that your
• 1:06
  hair doesn't actually turn grey.
• 1:08
  It grows grey.
• 1:10
  So every single strand of hair starts off completely white
• 1:13
  before pigment gets added.
• 1:14
  So when we say our hair turns grey, what we actually mean is the pigment
• 1:19
  system has stopped doing its job.
• 1:21
  Jen Oliver: So it's such a good distinction that be So the color
• 1:24
  we see is essentially being painted on during the growth process.
• 1:28
  Chris Smith: Exactly right.
• 1:29
  So we have specialized cells called melanocytes, and they sit inside
• 1:33
  each hair follicle and they inject pigment into the hair as it grows.
• 1:38
  And there are two types of pigment.
• 1:39
  We've got you melanin, which gives you the black and brown
• 1:42
  shades and fear melanin, which is responsible for blonde and red tones.
• 1:47
  Your unique combination of those two determines your natural hair color.
• 1:51
  Jamie Eynon: Hold on.
• 1:52
  That's actually kind of amazing.
• 1:53
  Thousands of tiny cells are just deciding what color our hair should be,
• 1:59
  Chris Smith: exactly a hundred thousand of them to be exact on the average head,
• 2:02
  Jen Oliver: I wonder who actually counted them.
• 2:05
  Each of them goes through repeated growth cycles as well.
• 2:08
  Melanin, it's regenerated at the start of each new cycle, but after roughly seven
• 2:13
  to 15 of those cycles, the production starts slowing down, doesn't it?
• 2:16
  So there's almost a built-in limit to the coloring.
• 2:20
  Jamie Eynon: 15 cycles.
• 2:21
  Sounds like a lot though.
• 2:22
  How long is each cycle?
• 2:24
  Chris Smith: So it's anywhere between two to seven years, depending on the person.
• 2:28
  So the maths is different for everyone, but eventually the pigment
• 2:31
  production starts winding down.
• 2:33
  Jen Oliver: Now, here's where a recent research has changed
• 2:36
  our understanding significantly.
• 2:38
  So there was a study published in Nature that revealed something incredible about
• 2:42
  the stem cells responsible for hair color.
• 2:45
  Why don't you tell us more, Chris?
• 2:47
  Chris Smith: Yeah, so this really was an important piece of research and
• 2:50
  what it told us was that melanocyte stem cells, which are the parent
• 2:53
  cells that produce your pigment making melanocytes, are uniquely mobile.
• 2:58
  They normally shuttle back and forth between different compartments within
• 3:02
  the hair follicle in one follicle compartment called the bulge.
• 3:05
  They sit dormant in another, uh, called the hair germ.
• 3:09
  They receive chemical signals from proteins that tell them to mature
• 3:13
  and start producing pigments.
• 3:14
  Jen Oliver: And the key finding was that as hair ages and the cycles repeatedly,
• 3:19
  these stem cells start getting physically stuck in the dormant compartments.
• 3:24
  So they start migrating to where the make pigment signals are.
• 3:28
  So they never get the instruction to actually produce the color.
• 3:32
  Jamie Eynon: So it's not that the cells actually die, they're
• 3:35
  just stuck in the wrong place.
• 3:37
  That's like having all the ingredients for dinner sitting in the cupboard,
• 3:40
  but nobody's walking to the kitchen to actually start cooking.
• 3:43
  Chris Smith: Yeah, that's a fair way to look at it actually.
• 3:45
  Um, and it's been described as those stem cells losing
• 3:47
  their chameleon-like function.
• 3:49
  And this is actually encouraging though because stuck cells
• 3:52
  are potentially fixable.
• 3:54
  Dead cells aren't, of course,
• 3:56
  Jen Oliver: but there's a second mechanism at work who isn't there.
• 3:59
  And this one involves something you'd normally associate with bleach in your
• 4:02
  hair, and that's hydrogen peroxide.
• 4:04
  Chris Smith: Absolutely.
• 4:05
  Right.
• 4:05
  And your hair follicles contain, um, and produce small amounts of this
• 4:10
  hydrogen peroxide naturally as a byproduct of normal cell activity.
• 4:14
  So under healthy conditions, an enzyme called catalyze, breaks it
• 4:18
  down into harmless water and oxygen.
• 4:20
  But as we age, catalyze levels decline so that hydrogen peroxide
• 4:24
  builds up and starts interfering with the pigment production process.
• 4:28
  Jen Oliver: And researchers at the University of Bradford, they
• 4:30
  confirm this when they analyzed pigmented hair versus grey hair.
• 4:35
  So the grey and white hair samples contained high
• 4:38
  levels of hydrogen peroxide.
• 4:40
  Whereas the pigmented hair had none, so effectively, your hair
• 4:44
  is being bleached from the inside,
• 4:46
  Jamie Eynon: so your own body is giving you highlights without your permission.
• 4:50
  That explains why grey hair often has a slightly different texture too.
• 4:54
  It's been chemically altered at its source.
• 4:56
  Mm,
• 4:57
  Chris Smith: it does.
• 4:57
  And the hydrogen peroxide doesn't just block pigment production.
• 5:00
  It also damages the repair mechanisms that would normally fix the problem.
• 5:04
  So it's created a compounding effect over time.
• 5:07
  Jen Oliver: Now one of the most interesting areas of research has
• 5:10
  been around stress and greying.
• 5:11
  So we've all heard that phrase, or you're giving me grey hair or
• 5:14
  you're gonna tear my hair grey.
• 5:16
  But there's actually science behind it, isn't there?
• 5:19
  Chris Smith: There is, and it's a fascinating piece of work here.
• 5:22
  So in 2020, researchers at Harvard published a study that provided.
• 5:27
  The first definitive, uh, mechanism linking psychological stress to grey hair.
• 5:32
  Jamie Eynon: So stress generally does make your hair go grey faster.
• 5:36
  Chris Smith: Yep, it does.
• 5:37
  And what the Harvard team found was that under acute stress, the
• 5:40
  sympathetic nervous system, that's your fight or flight system,
• 5:43
  releases a burst of norepinephrine directly into the hair follicle.
• 5:47
  And this causes a dormant melanocyte stem cells to activate prematurely,
• 5:52
  rapidly, use themselves up, and then they're gone permanently.
• 5:56
  Jen Oliver: And genetics play a huge role too, don't they?
• 5:58
  Of course.
• 5:59
  In how quickly you go grey.
• 6:01
  There was a study of over 6,000 people with diverse Latin American
• 6:05
  ancestry, and they identified a gene called the IRF four as the first gene,
• 6:10
  specifically associated with hair greying.
• 6:13
  So that gene is estimated to account for about 30% of greying with the remaining
• 6:18
  70% down to age stress environment.
• 6:22
  Jamie Eynon: So nearly a third of your grey hair timeline is written
• 6:25
  in your DNA before you are even born.
• 6:27
  That's reassuring or deeply annoying depending on your family photos.
• 6:31
  Jen Oliver: Yeah, there's nothing quite like a family album to give you
• 6:33
  a preview of the coming attractions.
• 6:36
  Chris Smith: Yeah.
• 6:36
  There are ethnic patterns too.
• 6:37
  So people of European descent tend to start greying in their mid thirties.
• 6:42
  Um, those of Asian descent.
• 6:44
  In their late thirties and people of African descent a bit later.
• 6:47
  So typically in their mid forties.
• 6:49
  Jen Oliver: And then there's premature greying, and that
• 6:51
  varies as well, doesn't it?
• 6:52
  So before 20 for Caucasians, before 25 for Asians, and before
• 6:57
  30 for people of African descent,
• 7:00
  Jamie Eynon: right?
• 7:01
  So going grey at 28 might be premature in one group and
• 7:04
  completely normal in another.
• 7:06
  It's another example of why universal health benchmarks don't always work.
• 7:11
  Chris Smith: Yeah, definitely.
• 7:11
  And for premature greying, specifically, nutritional deficiencies are a
• 7:15
  factor that's often overlooked.
• 7:16
  So, uh, vitamin B12 is particularly important 'cause that supports
• 7:21
  melanocyte function and deficiencies one of the most common nutritional
• 7:24
  causes of early greying.
• 7:25
  So studies have found significantly lower B12 levels in people
• 7:29
  experiencing premature greying.
• 7:32
  Jen Oliver: I wonder how many people are now adding B12 to
• 7:34
  their, their shopping basket.
• 7:36
  Copper's another one, isn't it?
• 7:38
  It's a co-factor for Ty Roese, and that's the key enzyme in melanin production.
• 7:43
  So if you've got low copper levels, that's been directly linked.
• 7:46
  With premature grey in iron and zinc and even vitamin D and calcium have
• 7:51
  also been flagged for research too.
• 7:53
  Jamie Eynon: So if you are going grey earlier than expected, it might be worth
• 7:57
  checking your nutrient revels rather than just blaming your grandparents.
• 8:01
  Chris Smith: Yeah, that's right.
• 8:02
  And, and in some cases, addressing the deficiency through diet
• 8:05
  or supplementation may help.
• 8:07
  Slow further greying.
• 8:09
  It's worth noting that reversing existing grey hair through
• 8:11
  nutrition alone is uncommon.
• 8:13
  The biggest benefit is in preventing further progression.
• 8:16
  Yeah,
• 8:16
  Jen Oliver: but the practical side of this, it's actually quite
• 8:19
  encouraging though, isn't it?
• 8:20
  Because while we can't change our genetics, we can absolutely
• 8:24
  influence the nutritional and lifestyle choices that we make.
• 8:27
  So making sure we're getting enough B12, maintaining good iron and copper levels,
• 8:33
  managing stress, getting enough sleep.
• 8:35
  I mean, these are all things within our control that affect the
• 8:38
  biology we've been chatting about.
• 8:40
  Jamie Eynon: Yeah, so basically eat well.
• 8:42
  Sleep well, stress less and your hair might.
• 8:45
  Thank you for it.
• 8:46
  Simple said no when living in the real world ever.
• 8:49
  But knowing the reasons behind it does make you take it a bit more seriously.
• 8:53
  Jen Oliver: Yeah.
• 8:53
  And there are some other factors that can accelerate things.
• 8:56
  So smoking's been associated with premature greying.
• 8:59
  Um, thyroid disorders can disrupt the melanocyte function.
• 9:03
  And there's also some autoimmune conditions that attack
• 9:06
  the melanocytes directly.
• 9:07
  Jamie Eynon: So what about reversing grey hair?
• 9:10
  Is it actually possible or are we firmly in the wishful thinking territory?
• 9:14
  Chris Smith: So it's not as far fetched as it once sounded.
• 9:17
  The NYU finding that GE mentioned earlier that stem cells get stuck
• 9:21
  rather than die is significant because it suggests that if we could persuade
• 9:25
  those cells to start moving again, pigment production could theoretically.
• 9:30
  Jen Oliver: There have been documented cases of individual grey hairs naturally
• 9:33
  re darkened into which shows that the process, it isn't always a one-way street.
• 9:39
  There was a small study in 2025 and they explored rose stem cell
• 9:44
  derived exosomes as a treatment, and a hundred percent of those patients
• 9:49
  achieve significant improvement.
• 9:51
  But the research is still in its very early stages, so.
• 9:54
  So what's this space?
• 9:56
  Jamie Eynon: So, so we're not there yet, but the door is open.
• 9:58
  Uh, that's more hopeful than you would've thought.
• 10:01
  Jen Oliver: Yep.
• 10:02
  And some medications used in cancer treatment, they've also been observed
• 10:05
  to trigger hair re pigmentation as a side effect, which has given
• 10:09
  researchers additional clues about which biological pathways are involved.
• 10:13
  Chris Smith: Yeah, that's right.
• 10:14
  And the, the closest someone is to the early stage of greying
• 10:17
  before that stem cell pool is fully depleted, the better the chances
• 10:20
  of any future treatment working.
• 10:22
  So there is a reason to be optimistic.
• 10:24
  Jen Oliver: Indeed, there is.
• 10:25
  So to answer our question, why does our hair turn grey?
• 10:30
  Chris Smith: So hair turns grey because the melanocyte stem cells responsible
• 10:34
  for producing pigment gradually lose their ability to function.
• 10:38
  They can become physically stuck in the wrong parts of the follicle
• 10:43
  hydrogen peroxide buildup and disrupt pigment making machinery.
• 10:47
  Stress can deplete the stem cell reservoir through the fight or flight response.
• 10:51
  And genetics set the overall pace of this greying process.
• 10:55
  Jamie Eynon: So your grey hairs aren't a sign of failure.
• 10:58
  They're a sign that roughly a hundred thousand tiny pigment operations have
• 11:02
  been running successfully for decades, and some of them are finally coming to an end.
• 11:08
  Jen Oliver: So that's why your hair turns grey.
• 11:11
  It's a combination of stem cell biology, oxidative chemistry, your nervous
• 11:16
  system, your genes, and even your nutritional status all working together.
• 11:21
  And the exciting part is that researchers are closer than ever to understanding
• 11:26
  whether some of it might be reversible.
• 11:30
  That's it for this week.
• 11:31
  Make sure you hit that subscribe button.
• 11:33
  We're unpacking the science behind everyday questions each week.
• 11:37
  Tell us in the comments what you'd like us to explore.
• 11:40
  Thanks for geeking out with us, but for now, that's it from me.
• 11:44
  Jamie Eynon: That's it from me.
• 11:45
  Chris Smith: And that's it from me.
• 11:46
  Jen Oliver: Bye for now.