Why is vitamin D so important to your body?
Maybe you've heard it helps with your bone health, your immune system, even calcium getting
involved and yes, we'll definitely talk about the sun and your skin getting involved in
the story about vitamin D but did you know that your liver and kidneys play a huge role
with vitamin D synthesis?
So, we'll take a look at those organs as well as answer some questions like, why are many
people deficient with this vitamin and how do you get adequate amounts inside of your
body?
It's going to be a fun one.
So, Let's do this.
[Intro]
Now, one of the characteristics of vitamin D is that it's a fat soluble vitamin.
Fat soluble vitamins dissolve in fats and tend to accumulate more in the body as compared
to say like the water soluble vitamins like vitamin C. Now, since we love our video quiz
questions, our video quiz question of the day is, can you name the four fat soluble
vitamins?
We already got the first one with vitamin D but if you can list the rest, post them
in the comments below and we'll pin the correct answer at the top of the comments.
Now, there are many compounds that belong to the vitamin D family and they all have
similar functions but by far the most important is vitamin D3 also known as Cholecalciferol.
Now, this can be synthesized in the skin but we need UV light to do it.
So, let's use this example down here on this skin dissection we have.
Where I'm tracing with the probe is the top layer of the skin called the epidermis and
this cut edge there, the majority of that is actually the second layer down called the
dermis but in the epidermis, we're going to see this other compound called 7-Dehydrocholesterol
and when the UV light comes down hits the epidermis, that 7-Dehydrocholesterol within
the epidermis gets converted to vitamin D3 and so, in theory, we could get all the vitamin
D3 that we needed from UV exposure.
We can also get it from our diet granted there's not a ton of foods that are just packed with
vitamin D but you find it in like fatty fish or fish oils and also in some of our fortified
products like we've fortified a lot of dairy products like milks and even fortified like
orange juice and you can even get it through supplementation but what's crazy to think
about is that there are still many people who are deficient with vitamin D3 or Cholecalciferol
and when you think about it from this perspective, say you live in the Northern Hemisphere and
you're one of those people that is exposed to those gnarly winters where the days get
shorter and you're inside more and you don't get a ton of sun exposure.
There are many situations with people where gutaneous synthesis or synthesis of vitamin
D in the skin ceases in the winter.
And so in that case, you'd have to get it through the diet or supplementation.
Now, another thing that I think is really interesting is if the skin pigment is darker
or I should say the darker the skin pigment, the longer it takes or the more some exposure
is needed to have that conversion process to take place and so, we're also seeing risk
factors in people who are elderly, if they're staying inside more, you also don't convert
things as efficiently when you're getting older in life.
I know it's a shame but one of the things to think about is how do I know if I'm deficient
because you don't really get symptoms until you get really severely deficient.
People with mild to moderate deficiency won't even know it and the answer to that, to knowing
this is you pretty much just gotta get tested which gives me a nice shameless segway to
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So, we've got this vitamin D3 or Cholecalciferol that was either synthesized in the skin or
ingested through our diet through food or supplementation but this is still not considered
the activated form of vitamin D3 and so, we need to actually have it go through a couple
conversion processes and that vitamin D3 whether it was ingested or synthesized in the skin,
it's going to be circulating throughout the blood and it will eventually pass through
this amazing organ here called the liver and I'm tracing the bottom portions of the liver
here and I'm just reflecting this muscle called the diaphragm that's draped over the liver
but once that vitamin D3, again known as Cholecalciferol makes it into the liver, it will start converting
it into something called 25 hydroxycholecalciferol and this is a really cool thing too that happens.
The liver has this feedback mechanism as the levels of that conversion go up as it's making
more 25 hydroxycholecalciferol, eventually it's going to shut off conversion even if
there's more vitamin D3 and this is a really cool way that the liver regulates the blood
levels of that new 25 hydroxycholecalciferol and the excess vitamin D that wasn't converted
can get stored in the liver.
So, that kind of creates this mechanism that if you ingest a high amount of vitamin D,
you can store the extra in that liver and so now you might be thinking okay, we've converted
it, totally active, right?
Nope, we still have other place and another conversion step that has to happen.
So now, this 25 hydroxycholecalciferol that was converted in the liver from the vitamin
D3 is going to go through the bloodstream again and eventually make it to another set
of organs called the kidneys.
If you take a look at this cool dissection here, we've got this frontal section through
this kidney and that 25 hydroxycholecalciferol is going to go through the bloodstream here
and eventually you can see those blood vessels branching and will eventually make it out
to the outer portion of the kidney referred to as the renal cortex and within that renal
cortex, there's this tiny little tubules called proximal convoluted tubules.
And inside those tubules under the direction of this hormone called parathyroid hormone,
the kidney will complete the final conversion into something called 125 dihydroxycholecalciferol.
The name just keeps getting longer but we're finally to this fully active form of vitamin
D and so it can start to its main effects but I do want to go back to that parathyroid
hormone that I mentioned, if I go to this other dissection here, this is a trachea or
your windpipe and here is your larynx which we nickname your Adam's apple.
So, me touching right there is the same as me touching here but I want to reference below
the larynx or the Adam's apple.
This structure or little organ called the thyroid gland.
And within the thyroid gland, you can't really see 'em but they're embedded in here are the
parathyroid glands.
The parathyroid glands, surprise surprise, secrete parathyroid hormone and parathyroid
hormone is all about regulating calcium levels in the blood.
So, in a way we can kind of think of this; parathyroid hormone is telling the kidney
"Hey, we need the final conversion of this vitamin D3 to its activated version so we
can get more calcium into the bloodstream".
Now you may have heard of this link before between vitamin D3 and calcium and here's
exactly what's going on here.
It's super cool. that converted 125 dihydroxycholecalciferol, you know it's kind of fun to say, will have
an effect on the digestive tract, specifically the small intestine but let me reflect this
fatty apron called the greater omentum and then you can see the small intestine in the
abdominal cavity here.
Now, again, the small intestine is a hollow tube where food is going to pass through and
be absorbed but again, keep in mind this is a hollow tube and the inside lining of that
tube has the cells that are going to be absorbing nutrients and in this case, we're going to
be talking calcium.
That 125 dihydroxycholecalciferol causes these intestinal cells to make more calcium binding
proteins so it'll bind the calcium and bring it into the body from the things that you've
ingested.
It's super amazing and calcium is so important to body functions.
Bone health is so important with calcium.
Also, for proper functioning, nervous tissue and muscle tissue calcium is important.
So, you can see this vitamin D3 going through this activation process so it can absorb this
calcium is so important and frankly quite amazing and because it is so amazing, I want
to take the chance to do a whiteboard session to make sure we're clear on all the steps
we just talked about.
So, we've got this area this box representing our skin and inside our skin we have the 7
dehydrocholesterol and as the beautiful rays of the sun shine upon our skin, that 7 dehydrocholesterol
gets converted into vitamin D3.
Now, this is one pathway.
We also ingest vitamin D3 through our diet, put it in our mouth, swallow it down, and
poof, both of these pathways will end up in the same place by going to the liver.
So, vitamin D3 once it's in the liver will get converted into the 25 hydroxycholecalciferol.
Now, I did mention there's this cool feedback mechanism with the liver that as the levels
of 25 hydroxycholecalciferol increase, eventually, the liver is going to be like, "Okey, let's
shut this conversion process from here to here down because we've got enough of this"
and any of the extra vitamin D3, say we're getting lots of sun exposure or we're ingesting
a lot in our diet, any of that extra vitamin D3 can be stored in the liver for later conversion
to start this process again when needed.
Now, once this is converted, it will eventually make it down into the kidneys and under the
direction of parathyroid gland, it secretes parathyroid hormone because again, parathyroid
gland is all about regulating calcium levels in the bloodstream, we'll get this conversion
of 25 hydroxycholecalciferol into the 125 dihydroxycholecalciferol.
Again, totally fun to say.
And the reason there's cute little stars here is because this is when we've got kind of
our activated form here.
This is where we're going to have some of the magic happen because this will then move
into the small intestine and that 125 dihydroxycholecalciferol will increase the number of calcium binding
proteins in the cells of the intestine - those cells that absorb nutrients.
And if we increase those proteins, we increase the amount of absorption and that's one of
our main functions of vitamin D. It's all about getting more calcium into the bloodstream
and like we said earlier, it's pretty amazing and if the effects of vitamin D on calcium
aren't amazing enough, there's some other potential effects that vitamin D can have
throughout your body.
I say "potential" because there's a need for more research and more information about how
these mechanisms work through vitamin D. For example, many of your immune cells have the
receptor for the activated form of vitamin D. So, it's thought that it may promote your
immune system, help with infections as well as inflammation.
There's also some laboratory studies that show that vitamin D may also inhibit the growth
of cancer cells.
So, some pretty cool things that we can look into through this amazing vitamin and let
me just come back to this discussion about vitamin D deficiency.
As we mentioned earlier, people with mild to moderate deficiencies often don't know
because they're asymptomatic.
Again, the only way to know in that situation is through proper testing.
But as the deficiency becomes more prolonged or more severe, then things can start to manifest
as symptoms and it most often manifest with the bones and because remember, when we have
vitamin - when we don't have vitamin D, we're not going to be able to absorb calcium into
the bloodstream but what happens is it gets pulled from the storage in the bone and then
bones can become weaker, you can get bone pain even easier fractures and sometimes people
can develop something called osteomalacia which is the softening of bone tissue.
Rickets is the kids version of osteomalacia and luckily because of our knowledge of this
and ability to supplement, we don't see that as much anymore but again, kind of this cool
thing to think about with vitamin D and I can get it from the sun if I want to and I
just have to mention one thing about that because I'm one of those people who burns
pretty easily and so I layer up with sunscreen which will inhibit vitamin D formation because
that sunscreen blocks out UV rays and so, it's kind of a mean trick I feel like it's
like this catch 22 where you're supposed to get some sun exposure but if you get too much
you're at a risk of cancer if you have lighter skin but luckily we've got those supplements.
Thanks for watching our video on vitamin D and Jeffrey the Skeleton, if you haven't noticed,
is extremely concerned about bone health and he thinks you should be too.
So, if you're interested in testing your vitamin D levels, be sure to check out that link in
the description below with today's sponsor LetsGetChecked and I'll give you guys 30%
off the vitamin D test as well as the other test that they offer.
Liking and subscribing definitely helps the channel, so we appreciate any of that and
we've got that quiz question you can answer in the comments below and I think I've covered
everything, so, we'll see you in the next video.