Jen Oliver: Welcome to the So that's Why Podcast, where we unpack the
science behind everyday questions.
I'm Jen.
Chris Smith: I'm Chris.
Matt Edmundson: And I'm Matt.
Jen Oliver: So today's question is why do we need vitamin D?
And I don't mean the vague, it's good for your bones answer.
I mean, what is it actually doing inside your body that
makes it absolutely essential?
Chris Smith: So vitamin D really is a super vitamin as we'll today.
In fact, it's not just a vitamin.
It also functions as a hormone.
'cause your body produces it.
It regulates genes and it has receptors in virtually every cell in our body.
Matt Edmundson: So vitamin D is actually a hormone.
Chris Smith: Yeah.
So it is still considered as a vitamin, but as you, your body can produce it and
it has hormone activity and function.
Many scientists now classify it as a hormone too.
Jen Oliver: So in this episode we'll discuss why vitamin D is
essential for everything from calcium absorption to immune function.
Why deficiency is so widespread despite us being able to make it from sunlight and
what happens when you don't get enough.
Matt Edmundson: Yeah.
'cause I've read right that nearly half.
Half of the global population is deficient in vitamin D. I mean, that's
a, that's a big old market right there.
You know, billions of people not having enough of something that their body
desperately needs to function properly.
So it does beg the question, doesn't it?
If we can make vitamin D from sunshine, why are almost half of
us on the planet still deficient?
Which is Sure.
Uh, I'm sure actually something that.
You guys are gonna get into.
Jen Oliver: So vitamin D deficiency isn't just about weak bones, it's
about why you might feel constantly exhausted, catch every bug going around
and struggle with muscle weakness.
It affects far more than people realize.
Chris Smith: Yeah, it's true.
And the consequences range from the obvious.
So bone diseases in children and adults, but to also to things we don't
traditionally think of in relation to vitamin D. So immune system
problems, as you mentioned, muscle weakness and increased infection risk.
Matt Edmundson: Okay, so let's start with the, the fundamental question here then.
What is vitamin D doing that makes it so crucial?
For me,
Chris Smith: its primary job is regulating calcium absorption, so your intestines
needed to effectively absorb that calcium,
Jen Oliver: and then you've got its role in the immune system.
Vitamin D controls, antimicrobial peptides, which are your first
defense against bacteria and viruses.
Matt Edmundson: So in mat language it gives your immune cells better
weapons to deal with it all.
Chris Smith: I like that.
Yeah.
E exactly.
Better weapons.
Sounds good.
Um, but cleverly it also prevents immune overreaction, so it promotes
regulatory cells that stop your immune system from attacking your own tissues.
That's why deficiency links to autoimmune disease risk.
Matt Edmundson: And again, my language.
So what this is doing is making your immune system more effective against
threats whilst preventing friendly fire.
Jen Oliver: Perfect description.
Matt Edmundson: Thank you.
Jen Oliver: It's about balance, not just strength.
Chris Smith: Absolutely.
And then we think about other things.
So if you think about muscles for a moment.
So vitamin D strength, vitamin D deficiency causes
proximal muscle weakness.
So those big muscles in your thighs and upper arms get notably weaker.
Matt Edmundson: So basically what you're saying is if we want big guns.
I need to take my vitamin D.
Jen Oliver: Exactly.
Matt Edmundson: There's another marketing slogan right there.
Jen Oliver: But in terms where that people might to relate, be able to
relate to better deficiency, can affect things like stair climbing, standing
up from chairs, you know, any movement that those big muscle groups need to do.
Chris Smith: It can.
And when it comes to healthy bones, we, we already know there's the link with
calcium absorption, but vitamin D also regulates what we call bone remodeling.
So this is the constant process of breaking down old bones and
building new bone without it.
Bones don't mineralize properly.
They're structurally there, but they're soft and weak.
Matt Edmundson: Mm. So is this where bowed legs and rickets come from?
Jen Oliver: Yeah.
Yeah, it does.
You know, bones deform under natural stress because they
haven't mineralized correctly.
They're not strong enough, are they?
Matt Edmundson: Okay.
So what then are the other issues associated with vitamin D deficiency
that we need to think about?
Chris Smith: There are loads and the implications are serious.
So without adequate Vitamin D, your body can only absorb about half the amount
of that dietary calcium that it should.
Matt Edmundson: So years of drinking milk for strong bones without checking,
maybe the vitamin D status might not be as effective as we think.
Chris Smith: Mm, absolutely.
It is essential to check that there is sufficient Vitamin D too.
And now a lot of milks, including plant milks, are typically
fortified with vitamin D for that.
Jen Oliver: Also the consequences of low vitamin D extend beyond calcium
and bone health too, don't they?
You know, vitamin D deficiency increases the risk of respiratory infections
and also contributes to tiredness.
Chris Smith: Yeah, it's always amazing how these things are all connected, isn't it?
So vitamin D manages all of these factors you mentioned simultaneously.
Matt Edmundson: So then how does you know, how does sunshine
actually make Vitamin D then?
That is something I'm curious about.
Chris Smith: So your skin contains a cholesterol derivative,
and what happens is when.
Ultraviolet light from the sun hits the skin.
It causes a conversion process that ultimately produces vitamin D three
that then travels to your liver and then to your kidneys as part of its journey
to become fully active in the body.
Jen Oliver: So it's a three stage production line, skin, liver,
kidneys, all driven by UV light.
And it's tightly regulated, isn't it, based on your, your body's calcium
needs, just like other hormones.
Matt Edmundson: So why is then.
As I said earlier, half the world's population is deficient.
Why is that?
If we can make vitamin D from sunlight, because half the world is
not, you know, deprived of the sun.
Significant, not
Jen Oliver: significant, is it?
Yeah.
Chris Smith: No, that's it.
And there are multiple factors coming to play here.
So vitamin D synthesis, it needs UV radiation, uh, but it's
gotta be at the right angle.
So we're typically talking about midday sun.
So if you live above, I think it's 35 degrees latitude, which is.
Effectively north of Los, Los Angeles, or of Southern Spain.
Winter sun never gets high enough, so your skin physically can't produce
vitamin C, uh, vitamin D, sorry, for several months of the year.
Matt Edmundson: So everyone in the UK basically, uh, Scandinavia, Canada,
these sorts of countries, they're at risk of not getting enough sun
to produce sufficient Vitamin D.
Is that right?
Chris Smith: It's true.
In fact, there was a bizarre stat for.
UK listeners only that apparently if you live north of Milton Keynes on
the average year, you don't get enough UV for the entirety of the year.
Matt Edmundson: Oh, wow.
Chris Smith: Wow.
Just to consistently Well, that
Matt Edmundson: that would be me.
I
live
north of
Milton Keyes.
Jen Oliver: Yeah, me too.
Chris Smith: Although we're had some sunny years recently.
Mm-hmm.
So maybe it's better.
Um, but it's more about your lifestyle actually, than anything.
Because even Sunny climates show high vitamin D deficiency
rates among their populations.
So if you look at the Middle East, for example, they've got a 65%.
Deficiency rate and that's due to staying indoors.
Mm-hmm.
Or covering up to escape the heat of the sun.
Even Australia, we think it's pretty sunny normally in Australia, right?
But their deficiency rates are really high and, and some areas of India
equally, they show near a hundred percent of the population in some
local areas to be vitamin D deficient.
Jen Oliver: And skin pigmentation matters as well, doesn't it?
'cause you've got melanin in your skin, which is your natural sun
protection chemical, and it helps.
Protect against sun damage, but it means darker skinned individuals
need more sun exposure to then produce the same amount of vitamin D.
Matt Edmundson: And I guess if you've got darker skin and you
live in a northern climate, that's like a double jeopardy, right?
Yeah.
Double challenge going on.
Jen Oliver: Exactly.
It's a genuine health equity issue that doesn't get enough attention, really.
Chris Smith: No, that's right.
And, and of course, age affects it too.
Uh, but what, what you might not realize is that someone in
their seventies would produce.
On average, only about a quarter of the vitamin DA 20-year-old would
make from the identical sun exposure.
Mm.
Matt Edmundson: So if you think then about, well, I think about the Aussies,
their vitamin D, they're deficient, they've got a lot of sunshine.
The thing that I hear banded about all the time is that's
because they wear sunscreen.
Is that a myth or is that true?
Chris Smith: So this notion that vitamin D is blocked by sunscreen wearing.
It's a complete myth.
So sunscreens do block a high percentage of that ultraviolet, BUVB raise, but not
all of them, which means enough of that UV gets through to our skin to allow it
to produce Vitamin D. And this is such an important topic because obviously
skin cancer is incredibly serious.
Mm-hmm.
So please do not believe rubbish spreading online that we shouldn't
wear sunscreen because of vitamin D.
It.
I, I, I appreciate it's a bigger topic, but please, please, if you're spending
time in the sun during the, the spring and summer months, wear sunscreen full stop.
You don't need to worry about vitamin D production in, in that situation.
So when it comes to the sun and avoided sun damage, the safest solution is
to cover up and stay outta the sun.
And of course, just take vitamin D supplements.
Matt Edmundson: So speaking then of the, the supplements that,
uh, we we're gonna be taking.
I see it more and more, you know, fortification, fortified
with vitamin D. Um, it seems to become a bigger and bigger thing.
Right?
Because I guess we've had to admit that our modern diets don't
naturally provide enough vitamin D.
Is that right?
Jen Oliver: Yeah.
I mean, many countries fortify milk and cereals, but you know, often
they still use vitamin D two because it's seen as the vegetarian option.
Um, because vitamin D three is usually from animals, but at Vegetology we wanted
an effective vitamin D three As D three is nearly 90% more effective than D two.
Um, but we wanted a vegan source, so that's why we developed our plant source D
three, which is one of our hero products.
Chris Smith: Oh, it sure is.
And importantly, testing has shown that our plant source vitamin D three.
Is directly equivalent to animal derived vitamin D three and just
as bioavailable, which means it does just the same job in the body.
The body basically can't tell the difference.
Matt Edmundson: Okay, so the source then of our vitamin D supplementation,
the D three, isn't as important as the molecular structure.
Jen Oliver: Exactly.
Plant derived, animal derived, or fish derived.
Vitamin D three is vitamin D three.
The key point is looking for vitamin D three from your supplement or
fortified food, not vitamin D two.
Matt Edmundson: Okay, that's very useful.
Uh, so let's get practical.
How much vitamin D three do we need?
Chris Smith: Yeah.
So this is frustrating because the figures are all over the place.
Um, in Europe, we now use what's known as the nutrient reference value
or NRV, which was previously the recommended daily amount, or RDA.
And that is in Europe is 200 international units per day of vitamin D. However,
many health institutes recommend more, they'll recommend 400 to 800
international units per day of vitamin D with some arguing even more than that.
So kind of 1000 to 2000 IU per day of vitamin D. So it really is all over the.
Jen Oliver: And I guess the recommended intakes are so varied because they,
they're in different places and they take into account average sun exposure,
age skin tones, and medical factors that can impact vitamin D level.
So it's a complicated picture.
Matt Edmundson: Okay.
So I guess the recommended daily amount, what did you call it?
The NRV?
I wish they'd just stick to one.
It just,
Jen Oliver: yeah,
I
know.
Chris Smith: I dunno what was wrong with RDA?
Everyone knew Recommended daily amount.
RDA.
Matt Edmundson: Yeah.
Makes sense.
Why change it?
Why change it Europe?
I have more questions for you, but that's one of them.
So I guess if the amounts is varied, my question would be,
can I take too much Vitamin D?
Chris Smith: Yeah.
So in Europe there is an established upper safe limit when it comes
to vitamin D and it's 4,000 IU or international units per day.
So that seems the maximum amount considered safer, ongoing
and continuous daily intake.
Matt Edmundson: Okay, so find a supplement then.
Of course the next problem is remember to take that supplement, right?
That can be the harder part.
Like, you know, gym memberships are great, aren't they?
They start well in January, but by March it's, it's not being used.
And I guess vitamin D is one of those where it could just be a bottle gathering
dust, uh, on the side of the counter.
Jen Oliver: Yeah.
But the good news is.
Vitamin D is fat soluble, so it's stored in your body.
So you do have a little bit of a buffer, but I don't think you can rely
on the summer sun, especially in the UK to carry you through the winter.
Matt Edmundson: Fair enough.
Okay, so we've talked about supplement centers a, a really sensible option,
um, especially if we're thinking about sensibly staying out of the sun.
What about food sources that can give us vitamin D.
Chris Smith: Yeah, so food sources really are limited.
So oily fish, egg yolk, and some meats contain a little vitamin
D, but even then, the levels are hit and miss and sometimes zero.
So it's challenging for everyone to get meaningful vitamin
D levels from food alone.
Especially, of course, vegans are vegetarians that
won't consume those items.
So plant sources in our diets are really limited in vitamin D levels.
So really we're looking at either fortified foods or for
most people, supplementation is the most reliable option.
Matt Edmundson: Okay, and this for us is where plant source
D three really matters, right?
Jen Oliver: Yeah, absolutely.
Especially for those that don't eat meat.
Plant source Vitamin D three means that nobody needs to
compromise either by missing out or using a less effective DD two.
Chris Smith: Yeah.
And it's worth pointing out that when you've got meats and dairy with vitamin
D, they've often been fortified.
So it's just the meat's taking a supplement rather than you,
I
Matt Edmundson: suppose that's what fortified means.
Jen Oliver: Yeah, yeah, yeah, yeah.
With added extras.
Chris Smith: Well, going back to the, the sun, obviously it's very important
for us, you know, sun exposure remains incredibly valuable for our health, but
it shouldn't be our only strategy when it comes to vitamin D. Um, especially in
those tima winter months, as I mentioned.
You're just not gonna get enough intensity.
Matt Edmundson: Yeah.
So the best strategy, I guess is whatever you'll actually stick to, like exercise,
just what can you do consistently?
Right,
Jen Oliver: exactly.
Daily supplement, weekly high dose or fortified foods plus supplementation.
You know, consistency beats perfection.
Chris Smith: Yep, it's true.
And um, if we look at how things connect, you've got sleep quality, for instance.
So vitamin D receptors exist in the brain areas, regulated sleep,
wake cycles, deficiency links to poor sleep and difficulty falling
asleep and reduced deep sleep.
Jen Oliver: And the immune connection affects both fighting
infections, preventing autoimmune conditions where your body basically
attacks its healthy tissue.
Chris Smith: That's it.
And if we go all the way back to muscle function that we talked about earlier.
Deficiency means muscles can't work optimally.
And that's regardless of the training that you do.
Jen Oliver: Exactly.
Fighting a handicap you might not know about.
Chris Smith: Yeah.
Yeah.
So vitamin D functions as the ultimate regulator in our body.
So it's constantly coordinating multiple biological systems, but these things
have a huge impact on our health.
Mm-hmm.
So it is so important.
Matt Edmundson: Yeah.
And it explains.
There's sort of the varied symptoms, doesn't it?
Fatigue, muscle weakness, free frequent infections, mood changes.
In effect, there are multiple systems we have running below capacity,
Jen Oliver: and with nearly half the world's population deficient.
This means that billions of people are at risk of conditions
that could be prevented.
Chris Smith: Yep.
And when it comes to vitamin D, supplementation's, one of
the most cost effective health interventions available anywhere.
If I, I mean, let's be honest, I dunno.
Anyone that works in the healthcare sector that doesn't take vitamin D supplements
themselves and no one that, uh, would not push the importance of vitamin D.
Jen Oliver: Mm-hmm.
Matt Edmundson: And understanding the why helps prioritize it, isn't it?
Because it's fair to say, traditionally the daily vitamin focus has always
been on vitamins like vitamin C rather than vitamin D three.
Jen Oliver: So why do we need vitamin D?
Because it's a vitamin and a hormone that regulates over a thousand genes.
It coordinates calcium absorption, it manages immune function, it helps
maintain muscle strength and influences cellular processes throughout your body.
Matt Edmundson: Yeah.
And nearly half of us don't have enough of this master regulator,
uh, but we keep calling it a vitamin, like it's just another
supplement when actually maybe it's.
I don't know.
Conducting your cellular orchestra.
Chris Smith: Cellular orchestra.
I like that.
That's one I've never heard before.
Matt Edmundson: Yeah, I'm, I'm trademarking it.
I just want you to know,
Jen Oliver: so that's why we need vitamin D. Checking levels and supplementing
when's needed isn't optional.
It's actually essential.
That's it for this week.
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Thanks for geeking out with us.
That's it from me.
Matt Edmundson: That's it
Chris Smith: from me.
Matt Edmundson: And that's it from me.
Jen Oliver: Bye for now.