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Jen Oliver: Welcome to the So that's
Why Podcast, where we unpack the

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science behind everyday questions.

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I'm Jen.

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Chris Smith: I'm Chris.

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Matt Edmundson: And I'm Matt.

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Jen Oliver: So today's question
is why do we need vitamin D?

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And I don't mean the vague,
it's good for your bones answer.

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I mean, what is it actually
doing inside your body that

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makes it absolutely essential?

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Chris Smith: So vitamin D really
is a super vitamin as we'll today.

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In fact, it's not just a vitamin.

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It also functions as a hormone.

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'cause your body produces it.

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It regulates genes and it has receptors
in virtually every cell in our body.

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Matt Edmundson: So vitamin
D is actually a hormone.

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Chris Smith: Yeah.

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So it is still considered as a vitamin,
but as you, your body can produce it and

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it has hormone activity and function.

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Many scientists now classify
it as a hormone too.

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Jen Oliver: So in this episode
we'll discuss why vitamin D is

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essential for everything from calcium
absorption to immune function.

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Why deficiency is so widespread despite
us being able to make it from sunlight and

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what happens when you don't get enough.

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Matt Edmundson: Yeah.

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'cause I've read right that nearly half.

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Half of the global population is
deficient in vitamin D. I mean, that's

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a, that's a big old market right there.

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You know, billions of people not having
enough of something that their body

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desperately needs to function properly.

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So it does beg the question, doesn't it?

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If we can make vitamin D from
sunshine, why are almost half of

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us on the planet still deficient?

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Which is Sure.

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Uh, I'm sure actually something that.

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You guys are gonna get into.

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Jen Oliver: So vitamin D deficiency
isn't just about weak bones, it's

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about why you might feel constantly
exhausted, catch every bug going around

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and struggle with muscle weakness.

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It affects far more than people realize.

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Chris Smith: Yeah, it's true.

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And the consequences
range from the obvious.

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So bone diseases in children and
adults, but to also to things we don't

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traditionally think of in relation
to vitamin D. So immune system

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problems, as you mentioned, muscle
weakness and increased infection risk.

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Matt Edmundson: Okay, so let's start with
the, the fundamental question here then.

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What is vitamin D doing
that makes it so crucial?

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For me,

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Chris Smith: its primary job is regulating
calcium absorption, so your intestines

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needed to effectively absorb that calcium,

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Jen Oliver: and then you've got
its role in the immune system.

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Vitamin D controls, antimicrobial
peptides, which are your first

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defense against bacteria and viruses.

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Matt Edmundson: So in mat language
it gives your immune cells better

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weapons to deal with it all.

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Chris Smith: I like that.

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Yeah.

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E exactly.

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Better weapons.

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Sounds good.

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Um, but cleverly it also prevents
immune overreaction, so it promotes

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regulatory cells that stop your immune
system from attacking your own tissues.

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That's why deficiency links
to autoimmune disease risk.

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Matt Edmundson: And again, my language.

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So what this is doing is making your
immune system more effective against

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threats whilst preventing friendly fire.

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Jen Oliver: Perfect description.

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Matt Edmundson: Thank you.

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Jen Oliver: It's about
balance, not just strength.

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Chris Smith: Absolutely.

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And then we think about other things.

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So if you think about
muscles for a moment.

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So vitamin D strength,
vitamin D deficiency causes

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proximal muscle weakness.

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So those big muscles in your thighs
and upper arms get notably weaker.

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Matt Edmundson: So basically what
you're saying is if we want big guns.

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I need to take my vitamin D.

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Jen Oliver: Exactly.

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Matt Edmundson: There's another
marketing slogan right there.

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Jen Oliver: But in terms where that
people might to relate, be able to

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relate to better deficiency, can affect
things like stair climbing, standing

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up from chairs, you know, any movement
that those big muscle groups need to do.

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Chris Smith: It can.

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And when it comes to healthy bones, we,
we already know there's the link with

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calcium absorption, but vitamin D also
regulates what we call bone remodeling.

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So this is the constant process
of breaking down old bones and

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building new bone without it.

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Bones don't mineralize properly.

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They're structurally there,
but they're soft and weak.

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Matt Edmundson: Mm. So is this where
bowed legs and rickets come from?

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Jen Oliver: Yeah.

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Yeah, it does.

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You know, bones deform under
natural stress because they

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haven't mineralized correctly.

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They're not strong enough, are they?

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Matt Edmundson: Okay.

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So what then are the other issues
associated with vitamin D deficiency

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that we need to think about?

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Chris Smith: There are loads and
the implications are serious.

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So without adequate Vitamin D, your body
can only absorb about half the amount

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of that dietary calcium that it should.

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Matt Edmundson: So years of drinking
milk for strong bones without checking,

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maybe the vitamin D status might
not be as effective as we think.

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Chris Smith: Mm, absolutely.

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It is essential to check that
there is sufficient Vitamin D too.

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And now a lot of milks, including
plant milks, are typically

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fortified with vitamin D for that.

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Jen Oliver: Also the consequences of
low vitamin D extend beyond calcium

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and bone health too, don't they?

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You know, vitamin D deficiency increases
the risk of respiratory infections

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and also contributes to tiredness.

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Chris Smith: Yeah, it's always amazing how
these things are all connected, isn't it?

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So vitamin D manages all of these
factors you mentioned simultaneously.

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Matt Edmundson: So then how
does you know, how does sunshine

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actually make Vitamin D then?

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That is something I'm curious about.

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Chris Smith: So your skin
contains a cholesterol derivative,

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and what happens is when.

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Ultraviolet light from
the sun hits the skin.

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It causes a conversion process that
ultimately produces vitamin D three

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that then travels to your liver and then
to your kidneys as part of its journey

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to become fully active in the body.

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Jen Oliver: So it's a three stage
production line, skin, liver,

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kidneys, all driven by UV light.

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And it's tightly regulated, isn't it,
based on your, your body's calcium

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needs, just like other hormones.

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Matt Edmundson: So why is then.

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As I said earlier, half the
world's population is deficient.

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Why is that?

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If we can make vitamin D from
sunlight, because half the world is

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not, you know, deprived of the sun.

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Significant, not

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Jen Oliver: significant, is it?

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Yeah.

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Yeah.

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Chris Smith: No, that's it.

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And there are multiple
factors coming to play here.

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So vitamin D synthesis, it
needs UV radiation, uh, but it's

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gotta be at the right angle.

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So we're typically
talking about midday sun.

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So if you live above, I think it's
35 degrees latitude, which is.

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Effectively north of Los, Los
Angeles, or of Southern Spain.

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Winter sun never gets high enough,
so your skin physically can't produce

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vitamin C, uh, vitamin D, sorry,
for several months of the year.

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Matt Edmundson: So everyone in the UK
basically, uh, Scandinavia, Canada,

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these sorts of countries, they're
at risk of not getting enough sun

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to produce sufficient Vitamin D.

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Is that right?

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Chris Smith: It's true.

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In fact, there was a bizarre stat for.

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UK listeners only that apparently if
you live north of Milton Keynes on

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the average year, you don't get enough
UV for the entirety of the year.

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Matt Edmundson: Oh, wow.

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Chris Smith: Wow.

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Just to consistently Well, that

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Matt Edmundson: that would be me.

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I

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live

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north of

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Milton Keyes.

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Jen Oliver: Yeah, me too.

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Chris Smith: Although we're
had some sunny years recently.

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Mm-hmm.

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So maybe it's better.

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Um, but it's more about your
lifestyle actually, than anything.

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Because even Sunny climates
show high vitamin D deficiency

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rates among their populations.

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So if you look at the Middle East,
for example, they've got a 65%.

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Deficiency rate and that's
due to staying indoors.

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Mm-hmm.

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Or covering up to escape
the heat of the sun.

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Even Australia, we think it's pretty
sunny normally in Australia, right?

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But their deficiency rates are really
high and, and some areas of India

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equally, they show near a hundred
percent of the population in some

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local areas to be vitamin D deficient.

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Jen Oliver: And skin pigmentation
matters as well, doesn't it?

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'cause you've got melanin in your
skin, which is your natural sun

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protection chemical, and it helps.

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Protect against sun damage, but it
means darker skinned individuals

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need more sun exposure to then
produce the same amount of vitamin D.

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Matt Edmundson: And I guess if
you've got darker skin and you

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live in a northern climate, that's
like a double jeopardy, right?

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Yeah.

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Double challenge going on.

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Jen Oliver: Exactly.

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It's a genuine health equity issue that
doesn't get enough attention, really.

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Chris Smith: No, that's right.

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And, and of course, age affects it too.

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Uh, but what, what you might
not realize is that someone in

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their seventies would produce.

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On average, only about a quarter
of the vitamin DA 20-year-old would

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make from the identical sun exposure.

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Mm.

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Matt Edmundson: So if you think then
about, well, I think about the Aussies,

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their vitamin D, they're deficient,
they've got a lot of sunshine.

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The thing that I hear banded
about all the time is that's

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because they wear sunscreen.

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Is that a myth or is that true?

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Chris Smith: So this notion that vitamin
D is blocked by sunscreen wearing.

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It's a complete myth.

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So sunscreens do block a high percentage
of that ultraviolet, BUVB raise, but not

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all of them, which means enough of that
UV gets through to our skin to allow it

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to produce Vitamin D. And this is such
an important topic because obviously

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skin cancer is incredibly serious.

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Mm-hmm.

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So please do not believe rubbish
spreading online that we shouldn't

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wear sunscreen because of vitamin D.

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It.

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I, I, I appreciate it's a bigger topic,
but please, please, if you're spending

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time in the sun during the, the spring and
summer months, wear sunscreen full stop.

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You don't need to worry about vitamin
D production in, in that situation.

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So when it comes to the sun and avoided
sun damage, the safest solution is

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to cover up and stay outta the sun.

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And of course, just take
vitamin D supplements.

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Matt Edmundson: So speaking then
of the, the supplements that,

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uh, we we're gonna be taking.

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I see it more and more, you
know, fortification, fortified

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with vitamin D. Um, it seems to
become a bigger and bigger thing.

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Right?

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Because I guess we've had to
admit that our modern diets don't

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naturally provide enough vitamin D.

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Is that right?

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Jen Oliver: Yeah.

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I mean, many countries fortify milk
and cereals, but you know, often

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they still use vitamin D two because
it's seen as the vegetarian option.

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Um, because vitamin D three is usually
from animals, but at Vegetology we wanted

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an effective vitamin D three As D three
is nearly 90% more effective than D two.

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Um, but we wanted a vegan source, so
that's why we developed our plant source D

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three, which is one of our hero products.

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Chris Smith: Oh, it sure is.

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And importantly, testing has shown
that our plant source vitamin D three.

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Is directly equivalent to animal
derived vitamin D three and just

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as bioavailable, which means it
does just the same job in the body.

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The body basically can't
tell the difference.

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Matt Edmundson: Okay, so the source
then of our vitamin D supplementation,

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the D three, isn't as important
as the molecular structure.

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Jen Oliver: Exactly.

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Plant derived, animal
derived, or fish derived.

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Vitamin D three is vitamin D three.

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The key point is looking for vitamin
D three from your supplement or

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fortified food, not vitamin D two.

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Matt Edmundson: Okay, that's very useful.

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Uh, so let's get practical.

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How much vitamin D three do we need?

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Chris Smith: Yeah.

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So this is frustrating because the
figures are all over the place.

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Um, in Europe, we now use what's
known as the nutrient reference value

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or NRV, which was previously the
recommended daily amount, or RDA.

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And that is in Europe is 200 international
units per day of vitamin D. However,

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many health institutes recommend
more, they'll recommend 400 to 800

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international units per day of vitamin
D with some arguing even more than that.

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So kind of 1000 to 2000 IU per day of
vitamin D. So it really is all over the.

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Jen Oliver: And I guess the recommended
intakes are so varied because they,

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they're in different places and they
take into account average sun exposure,

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age skin tones, and medical factors
that can impact vitamin D level.

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So it's a complicated picture.

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Matt Edmundson: Okay.

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So I guess the recommended daily
amount, what did you call it?

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The NRV?

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I wish they'd just stick to one.

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It just,

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Jen Oliver: yeah,

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I

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know.

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Chris Smith: I dunno
what was wrong with RDA?

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Everyone knew Recommended daily amount.

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RDA.

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Matt Edmundson: Yeah.

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Makes sense.

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Why change it?

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Why change it Europe?

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I have more questions for
you, but that's one of them.

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So I guess if the amounts is
varied, my question would be,

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can I take too much Vitamin D?

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Chris Smith: Yeah.

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So in Europe there is an established
upper safe limit when it comes

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to vitamin D and it's 4,000 IU
or international units per day.

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So that seems the maximum
amount considered safer, ongoing

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and continuous daily intake.

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Matt Edmundson: Okay, so
find a supplement then.

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Of course the next problem is remember
to take that supplement, right?

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That can be the harder part.

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Like, you know, gym memberships
are great, aren't they?

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They start well in January, but by
March it's, it's not being used.

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And I guess vitamin D is one of those
where it could just be a bottle gathering

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dust, uh, on the side of the counter.

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Jen Oliver: Yeah.

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But the good news is.

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Vitamin D is fat soluble,
so it's stored in your body.

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So you do have a little bit of a
buffer, but I don't think you can rely

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on the summer sun, especially in the
UK to carry you through the winter.

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Matt Edmundson: Fair enough.

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Okay, so we've talked about supplement
centers a, a really sensible option,

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um, especially if we're thinking
about sensibly staying out of the sun.

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What about food sources
that can give us vitamin D.

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Chris Smith: Yeah, so food
sources really are limited.

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So oily fish, egg yolk, and some
meats contain a little vitamin

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D, but even then, the levels are
hit and miss and sometimes zero.

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So it's challenging for everyone
to get meaningful vitamin

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D levels from food alone.

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Especially, of course,
vegans are vegetarians that

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won't consume those items.

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So plant sources in our diets are
really limited in vitamin D levels.

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So really we're looking at
either fortified foods or for

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most people, supplementation
is the most reliable option.

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Matt Edmundson: Okay, and this
for us is where plant source

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D three really matters, right?

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Jen Oliver: Yeah, absolutely.

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Especially for those that don't eat meat.

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Plant source Vitamin D three
means that nobody needs to

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compromise either by missing out
or using a less effective DD two.

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Chris Smith: Yeah.

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And it's worth pointing out that when
you've got meats and dairy with vitamin

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D, they've often been fortified.

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So it's just the meat's taking
a supplement rather than you,

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I

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Matt Edmundson: suppose
that's what fortified means.

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Jen Oliver: Yeah, yeah, yeah, yeah.

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With added extras.

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Chris Smith: Well, going back to the,
the sun, obviously it's very important

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for us, you know, sun exposure remains
incredibly valuable for our health, but

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it shouldn't be our only strategy when
it comes to vitamin D. Um, especially in

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those tima winter months, as I mentioned.

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You're just not gonna
get enough intensity.

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Matt Edmundson: Yeah.

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So the best strategy, I guess is whatever
you'll actually stick to, like exercise,

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just what can you do consistently?

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Right,

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Jen Oliver: exactly.

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Daily supplement, weekly high dose or
fortified foods plus supplementation.

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You know, consistency beats perfection.

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Chris Smith: Yep, it's true.

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And um, if we look at how things connect,
you've got sleep quality, for instance.

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00:14:52,488 --> 00:14:56,478
So vitamin D receptors exist in
the brain areas, regulated sleep,

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wake cycles, deficiency links to
poor sleep and difficulty falling

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00:15:00,978 --> 00:15:02,898
asleep and reduced deep sleep.

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00:15:03,378 --> 00:15:05,448
Jen Oliver: And the immune
connection affects both fighting

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infections, preventing autoimmune
conditions where your body basically

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attacks its healthy tissue.

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Chris Smith: That's it.

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And if we go all the way back to muscle
function that we talked about earlier.

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00:15:15,378 --> 00:15:17,448
Deficiency means muscles
can't work optimally.

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00:15:17,658 --> 00:15:19,428
And that's regardless of
the training that you do.

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00:15:19,728 --> 00:15:20,268
Jen Oliver: Exactly.

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00:15:20,268 --> 00:15:22,518
Fighting a handicap you
might not know about.

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00:15:22,518 --> 00:15:22,728
Chris Smith: Yeah.

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00:15:23,568 --> 00:15:23,808
Yeah.

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00:15:23,838 --> 00:15:26,928
So vitamin D functions as the
ultimate regulator in our body.

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00:15:26,958 --> 00:15:32,538
So it's constantly coordinating multiple
biological systems, but these things

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have a huge impact on our health.

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Mm-hmm.

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00:15:34,158 --> 00:15:35,088
So it is so important.

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00:15:35,598 --> 00:15:35,868
Matt Edmundson: Yeah.

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And it explains.

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00:15:37,683 --> 00:15:39,573
There's sort of the varied
symptoms, doesn't it?

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00:15:39,573 --> 00:15:43,713
Fatigue, muscle weakness, free
frequent infections, mood changes.

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00:15:44,103 --> 00:15:48,603
In effect, there are multiple systems
we have running below capacity,

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Jen Oliver: and with nearly half
the world's population deficient.

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00:15:52,413 --> 00:15:55,263
This means that billions of
people are at risk of conditions

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00:15:55,293 --> 00:15:56,523
that could be prevented.

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00:15:57,393 --> 00:15:57,663
Chris Smith: Yep.

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And when it comes to vitamin
D, supplementation's, one of

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00:16:00,123 --> 00:16:03,663
the most cost effective health
interventions available anywhere.

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00:16:04,398 --> 00:16:06,078
If I, I mean, let's be honest, I dunno.

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00:16:06,108 --> 00:16:09,168
Anyone that works in the healthcare sector
that doesn't take vitamin D supplements

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00:16:09,168 --> 00:16:13,758
themselves and no one that, uh, would
not push the importance of vitamin D.

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00:16:13,818 --> 00:16:14,118
Jen Oliver: Mm-hmm.

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00:16:14,598 --> 00:16:17,508
Matt Edmundson: And understanding the
why helps prioritize it, isn't it?

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00:16:17,508 --> 00:16:22,578
Because it's fair to say, traditionally
the daily vitamin focus has always

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00:16:22,578 --> 00:16:26,388
been on vitamins like vitamin
C rather than vitamin D three.

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00:16:27,108 --> 00:16:29,478
Jen Oliver: So why do we need vitamin D?

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00:16:29,913 --> 00:16:34,023
Because it's a vitamin and a hormone
that regulates over a thousand genes.

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00:16:34,023 --> 00:16:38,853
It coordinates calcium absorption,
it manages immune function, it helps

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00:16:38,853 --> 00:16:44,013
maintain muscle strength and influences
cellular processes throughout your body.

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00:16:44,613 --> 00:16:44,943
Matt Edmundson: Yeah.

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And nearly half of us don't have
enough of this master regulator,

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00:16:51,363 --> 00:16:55,263
uh, but we keep calling it a
vitamin, like it's just another

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00:16:55,263 --> 00:16:58,173
supplement when actually maybe it's.

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00:16:58,548 --> 00:16:58,968
I don't know.

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00:16:58,968 --> 00:17:01,278
Conducting your cellular orchestra.

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00:17:02,118 --> 00:17:03,198
Chris Smith: Cellular orchestra.

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00:17:03,198 --> 00:17:03,708
I like that.

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00:17:03,708 --> 00:17:04,908
That's one I've never heard before.

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00:17:04,968 --> 00:17:06,588
Matt Edmundson: Yeah,
I'm, I'm trademarking it.

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00:17:06,588 --> 00:17:07,218
I just want you to know,

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00:17:08,598 --> 00:17:13,338
Jen Oliver: so that's why we need vitamin
D. Checking levels and supplementing

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00:17:13,338 --> 00:17:15,288
when's needed isn't optional.

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It's actually essential.

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That's it for this week.

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Hit subscribe.

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00:17:19,638 --> 00:17:23,028
We're unpacking science behind
everyday questions weekly.

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Tell us in the comments what
you'd like us to explore.

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Thanks for geeking out with us.

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00:17:27,978 --> 00:17:28,848
That's it from me.

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Matt Edmundson: That's it

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00:17:29,508 --> 00:17:29,898
Chris Smith: from me.

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00:17:30,258 --> 00:17:31,188
Matt Edmundson: And that's it from me.

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Jen Oliver: Bye for now.