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What Is Vitamin D & Vitamin D Deficiency? | Nutritionist Explains... | Myprotein
Jan 30, 2025
Our expert nutritionist breaks down everything you need to know about vitamin D, including how much vitamin D you need and the dangers of vitamin D deficiency.
Nutritional consultant and PhD researcher, Richie Kirwan, is back with another bite-sized nutrition session for you, all about the powers of that sunshine vitamin everyone could probably do with a bit more of.
It’s an essential vitamin that plays a role in so many vital functions of the body, from your immune system to muscle function, so it’s pretty important you’re getting your recommended daily dose.
Watch the video to find out more.
Still got questions? Let us know in the comments below.
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Chapters:
00:00 – Intro
00:50 – How do we make vitamin D?
03:27 – Food sources of vitamin D
04:33 – What is vitamin D deficiency?
04:55 – Why is vitamin D important?
07:21 – Do you need a vitamin D supplement?
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0:00
vitamin d what can't it do right well
0:02
actually
0:03
what does it do in this video i'm going
0:04
to tell you exactly what you need to
0:06
know
0:06
about the sunshine
0:08
[Music]
0:14
how's it going guys my name is richie
0:15
kerwin and i'm a nutritionist and
0:16
nutrition researcher
0:18
at liverpool john moores university and
0:19
you're watching the my protein youtube
0:21
channel
0:21
this is a channel that brings you need
0:23
to know info on how to fuel your body
0:24
and train
0:25
to be your strongest self today we're
0:27
going to talk all about a vitamin that i
0:28
think
0:29
most people should consider
0:30
supplementing with vitamin d i'll tell
0:32
you how we make it
0:33
why we don't make enough what it does
0:36
and how much you should consider taking
0:38
as always i want to point out that i'm
0:39
not recommending
0:40
any particular vitamin d supplements
0:42
what i am going to do
0:44
is talk about how vitamin d works and
0:46
what to look out for
0:47
when looking for a supplement let's
0:48
start with the basics vitamin d is a fat
0:51
soluble vitamin which means it dissolves
0:53
and can be stored in fat
0:54
that makes it different from
0:55
water-soluble vitamins like b and c
0:57
because they can't be stored in our
0:58
bodies and any excess that we eat
1:00
gets peed out fat soluble vitamins can
1:03
be stored in our bodies this is good
1:04
because it means we can store any extra
1:06
vitamin d we make or we get from the sun
1:08
but it does have one negative side
1:09
effect
1:10
if we eat way more than we need we can
1:12
store so much that it can become toxic
1:14
in the body and have some serious
1:15
negative health effects this is called
1:17
hypervitaminosis
1:18
d and you do not want it to happen to
1:20
you just to give you all an
1:22
easy reference value the recommended
1:23
daily intake for vitamin d3 in the uk
1:26
is 10 micrograms as there are some
1:28
different forms of vitamin d we also
1:30
measure using
1:30
international units which standardize
1:32
the effects of the different forms of
1:34
the vitamin
1:34
10 micrograms of vitamin d is the same
1:37
as 400
1:38
international units vitamin d is a very
1:41
interesting vitamin because we can make
1:42
it in
1:43
our skin when we're exposed to sunlight
1:45
specifically ultraviolet b
1:46
or uvb rays in our body we use
1:49
cholesterol to form a substance called
1:50
seven dehydrocholesterol when our skin
1:53
is exposed to sunlight the seven
1:54
dehydrocholesterol just under our skin
1:57
gets converted to pre-vitamin d3 which
1:59
then
2:00
gets converted to colicle this then gets
2:03
converted to calcidial in the liver
2:05
otherwise known as 25
2:06
ohd tree which is what we use to measure
2:09
serum vitamin d levels
2:11
finally this gets converted to the
2:12
active form calcitriol
2:14
in the kidneys try dropping that into
2:16
dinner conversation sometimes
2:17
you are guaranteed to never get invited
2:19
back the great thing about producing
2:20
vitamin d in our skin
2:22
is that our body has a feedback system
2:23
in place that stops you producing too
2:25
much vitamin d from sunlight
2:27
so there's no worries of producing too
2:28
much from sun alone the problem with
2:30
producing vitamin d from sun is we just
2:32
don't get enough of it you see someone
2:34
could
2:34
probably make enough vitamin d from
2:36
sunshine if they get up to 30 minutes of
2:38
sun exposure
2:39
twice a week over their face arms and
2:41
legs if they're very fair-skinned
2:43
and if they're relatively young do you
2:45
meet all those criteria the problem is
2:47
we all spend a lot of times indoors or
2:49
pretty much
2:49
all of 2020 and when we do leave the
2:51
house we're usually fully clothed at
2:52
least i hope you are
2:53
we often travel around in cars glass
2:55
filters out uvb rays so you're not
2:57
producing any in the car
2:58
and if you live far from the equator
2:59
like in ireland or the uk we only get
3:01
enough uvb
3:02
rays to produce vitamin d in the summer
3:05
on top of that
3:06
if someone has a darker complexion like
3:08
someone of sub-saharan african or
3:10
south indian origin the melanin in your
3:12
skin makes producing vitamin d
3:14
much harder compared to people with
3:16
lighter skin especially for those living
3:18
far away from the equator
3:19
and if you're older we know that older
3:21
people aren't able to produce vitamin d
3:23
from sunlight
3:23
as well as younger people so getting it
3:25
from sunlight isn't easy what about from
3:27
food
3:27
well that's an even worse story
3:29
unfortunately there are very few good
3:31
sources of vitamin d in our diet
3:33
it's found in meat eggs or dairy but not
3:35
in high amounts to give you an idea of
3:37
how much is in meat depending on the cut
3:40
and the animal's feed
3:41
beef steak has around 5 micrograms of
3:43
vitamin d per kilo
3:45
which means you'd need to eat two
3:46
kilograms of steak just to get your
3:48
daily amount of vitamin d dairy products
3:50
often have
3:51
less and that's why they are often
3:53
fortified with vitamin d
3:54
to prevent deficiency egg yolks are a
3:56
little better but you'd still need
3:58
around 250 grams of pure egg yolk
4:00
just to meet your daily dose now animal
4:03
liver can be a good source of vitamin d
4:06
as can some oily fish and fish liver but
4:08
not many people are willing to eat fish
4:10
liver to get enough vitamin d as for
4:12
non-animal sources
4:13
you can get mushrooms that are grown
4:14
under special uv lamps that increases
4:16
their vitamin d content
4:18
but that's about it in fact the form of
4:20
vitamin d produced in mushrooms and used
4:22
in some supplements
4:22
is called ergocalciferol or vitamin d2
4:25
and while it still is a form of vitamin
4:26
d
4:27
it's not as efficiently converted to the
4:28
active form as vitamin d3 and this is
4:31
why vitamin d deficiency is so
4:33
common insufficient vitamin d is
4:34
considered to be serum levels below
4:36
50 nanomoles per liter so if you have
4:38
above that you're considered to be
4:40
vitamin d sufficient the problem is
4:42
more than 40 of europeans have levels
4:45
below that
4:45
and actually 13 have levels below
4:49
30 nanomoles per liter vitamin d
4:51
deficiency is actually considered to be
4:53
a global health
4:54
problem so we don't get enough why does
4:56
that even matter well like i said
4:58
vitamin d is a very special vitamin and
5:00
one of the reasons for that is something
5:01
called the vitamin d
5:03
receptor the vitamin d receptor is a
5:05
nuclear receptor which means that
5:06
vitamin d
5:07
binds with it and then regulates the
5:08
expression of specific genes
5:10
that's important because the vitamin d
5:12
receptor is found in virtually every
5:14
tissue in the body which means that
5:15
vitamin d has a big
5:17
role to play in our health one of
5:18
vitamin d's most famous roles is in
5:21
bone health and this is because of its
5:23
regulation of our blood calcium levels
5:25
vitamin d helps to increase the
5:26
absorption of calcium from our gut
5:28
when blood calcium levels drop it helps
5:30
to absorb more calcium from our kidneys
5:32
before we pee it out and can even take
5:34
calcium from our bones if we need it
5:36
this is because
5:36
the level of calcium in our blood needs
5:38
to be maintained at a specific level
5:40
and it's essential to many processes in
5:43
our body
5:44
like nerve transmission and muscle
5:45
contraction because of its role
5:47
in calcium metabolism vitamin d is
5:48
essential for building a strong skeleton
5:50
and lower vitamin d levels are
5:51
associated with lower bone mineral
5:53
density
5:54
and a greater risk of fractures in both
5:56
younger and older people but vitamin d
5:58
is
5:58
so much more than bone health it's so
6:01
important that low levels of vitamin d
6:02
are associated with higher rates of
6:04
cardiovascular disease high blood
6:06
pressure diabetes
6:07
and other cardiometabolic conditions
6:09
this is because vitamin d has an
6:10
important role to play in both
6:11
insulin sensitivity how we process
6:13
glucose and the health of our body's
6:15
fat stores on top of that vitamin d has
6:18
a massive role to play in our body's
6:20
immune system
6:21
helping us to fight off disease and low
6:23
vitamin d levels are even associated
6:25
with greater risk of autoimmune disease
6:26
you've all probably heard of vitamin d
6:28
being really good for upper respiratory
6:30
tract infections this
6:32
is true as supplementing is associated
6:34
with lower rates of infection but many
6:35
of these studies aren't based around
6:37
covet infection just respiratory tract
6:39
infections in general here's an
6:40
important aspect of nutrition science
6:42
we can say very little for definite when
6:44
we talk about the effect of a specific
6:46
nutrient on a specific disease
6:48
we can only talk about risk so for
6:50
example we can't say that
6:51
having sufficient vitamin d levels would
6:52
prevent someone from getting a disease
6:55
but we can say that it reduces their
6:57
chances of getting
6:58
it reduces the potential risk but it's
6:59
not a guaranteed protection that's
7:01
something people get wrong with
7:02
nutrition science
7:04
all the time vitamin d also has a major
7:06
role to play in
7:07
muscle growth and higher levels of
7:09
vitamin d are associated with higher
7:11
levels of testosterone
7:12
greater muscle mass strength and
7:14
physical function because of all this
7:16
higher levels of vitamin d are also
7:18
associated with a lower risk of death as
7:20
we age
7:21
so it sounds like vitamin d is pretty
7:23
important right and seeing as we don't
7:24
get much from our diet or sunlight
7:26
especially in ireland and the uk
7:27
supplementing is probably a good idea
7:30
here's the thing
7:31
a lot of vitamin d supplement trials
7:33
don't show any benefits and that's
7:35
probably because they don't supplement
7:37
enough to raise serum levels remember
7:39
vitamin d insufficiency is when serum
7:42
levels are below 50 nanomoles per liter
7:44
so getting your levels above that is
7:46
important if your vitamin d levels are
7:48
quite low
7:48
that might take some time that's why
7:50
many people like to get their vitamin d
7:52
levels tested so they know what their
7:53
current levels are
7:55
and then they can retest after a year to
7:57
see if their supplementation has worked
7:59
that's also a really good way to make
8:01
sure you don't get too
8:02
much vitamin d which can be really bad
8:05
for your health
8:06
from a dosage perspective the current uk
8:08
recommendation of 400
8:09
international units is probably not
8:11
going to increase your serum levels much
8:12
at all
8:13
to be honest most multivitamins contain
8:15
this amount and hoping that this will
8:17
raise serum vitamin d levels is like
8:19
hoping to put out a forest fire by
8:21
peeing on it
8:23
you can try but you won't get very far
8:25
that's why higher doses of vitamin d3
8:27
may be better up as far as the upper
8:29
recommended dosage of 4
8:31
000 international units in fact if you
8:33
get a blood test and your serum vitamin
8:35
d levels are very low
8:37
your doctor may even prescribe you an
8:39
even higher dose vitamin d supplement
8:41
until your serum levels increase like i
8:43
said the best way to know your vitamin d
8:45
level is to get tested
8:46
in the meantime supplementing with a
8:47
daily dose as much as the upper uk limit
8:50
of 4 000 international units of d3
8:52
may be enough to help prevent
8:55
insufficiency so what do you think
8:56
did that clear things up for you about
8:58
vitamin d as always if you have any
9:00
questions let me know in the comments
9:01
below and remember to like and subscribe
9:03
to my protein youtube channel
9:04
for more great evidence-based
9:06
information
9:08
[Music]
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