Vitamin D deficiency is a really common problem worldwide.
About a billion people around the world don’t get enough Vitamin D, which is weird because
the main way that we get Vitamin D is through sunlight.
Big picture: Vitamin D is what's called an essential nutrient, a nutrient that the body
doesn’t make entirely on its own, so it has to get it from some other source.
And there are two types: Vitamin D2 that we need to eat and Vitamin D3 which we get from
sunlight or from foods like salmon or fortified milk.
Neither of these previtamins actually do anything before being metabolized by the liver and
kidneys, but we’ll get to that.
Either way, we can make Vitamin D, but we have to work for it.
So let’s shed some light on the situation.
Couldn’t resist the pun.
Okay, we don’t care about visible light from the sun, we care about the higher energy
ultraviolet radiation, or UV light.
Specifically, this part of UV called UVB.
This is the same type that causes sunburns and skin cancer, but in small doses it’s
fine.
Which sound a lot like my attempts at humor.
When UVB hits your skin, it stimulates a molecule in your skin called 7-dehydrocholesterol.
This guy transforms into D3.
You could also eat a bunch of fatty fish and get D3, but either way, at this step, you’ve
got a molecule called cholecalciferol, which doesn’t do anything yet.
It has to go to the liver where its metabolized into a more useful form called 25-hydroxyvitamin
D3, then the kidney converts it into a hormone called calcitriol which is the form that can
actually do stuff.
Some studies show that the vascular wall within blood vessels can do these conversions too,
but at a much smaller level.
But we end up with a vitamin D hormone, which is what throws people off.
Remember, a hormone is just a chemical that's secreted by a gland that travels through the bloodstream
that have an effect somewhere else.
And as a hormone, it subject to feedback loops and increased or decreased production when
it’s needed, which it’s actually really good at.
And you’ve probably heard of one of its biggest uses in the body — calcium absorption.
Ever notice that milk always has vitamin D in it?
That’s to help your body absorb calcium.
Here’s the thing though, Hormone D has receptors on most of the cells in your body.
So it’s way more useful that just helping you with calcium absorption.
According to a 2010 article in the journal Diabetes, people with low amounts of Vitamin
D had a 60% higher chance of heart disease than people with higher concentrations.
Same goes for high blood pressure.
Lower Vitamin D is heavily correlated with increased blood pressure.
Vitamin D also has a role in brain function and might help against depression.
One study in 2008 found that a year of Vitamin D supplementation significantly improved symptoms
of depression.
This was in pill form, not sunlight, so any improved mood wasn’t from lifestyle changes.
Point is, Vitamin D is so much more useful than just helping with calcium absorption.
It can help make insulin, stimulate our immune system, it’s involved in gene regulation,
and can even help in preventing certain cancers.
Which is ironic considering the whole sunlight and skin cancer thing.
A couple things to keep in mind though.
Like as you get older, your ability to crank out D3 from sunlight goes down.
So if you’re an older adult, you may need a bit more sun to get their vitamin D.
Luckily, that’s not a problem in America.
Looking at you Florida.
Plus, if you have darker skin, you have more of a pigment called melanin.
This pigment absorbs UVB, which is good news because your skin has a naturally higher sun
protection factor, but it also means you’re more likely to have vitamin D deficiency.
So folks with darker skin have to balance the D3 they get from diet along with sun exposure
making sure they’re not overdoing it on either.
Exposure to sunlight is still our most efficient way of making Vitamin D, and that process
starts in our skin, which is something I wanted to underline.
Because oftentimes we see our skin as just like, a protective layer.
When in reality it’s the largest organ in our body and it’s really active in homeostasis.
I’ve got a bunch of traditional anatomy and physiology learning videos scheduled for
the fall.
I’m still writing those.
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Have fun, be good.