How Our Bodies Make Vitamin D | Corporis
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How Our Bodies Make Vitamin D | Corporis

December 22, 2019

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. Also, all of these videos go out a few days
earlier for Patrons, if you’re into that, click here. Otherwise, subscribe and hit the bell for
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here. Have fun, be good.

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  1. The public health message clearly went too far on the sun avoidance message and led to a lot of vitamin D deficiency and everyone got started on supplements but now as far as I understand there's been little evidence it's really helped with anything. Basically this shitty place has too little sun.

  2. So interesting! Be getting my Texas sunshine by the pool tomorrow after taking my Vitamin D supplement.. good stuff!

  3. Welcome to Canada – where 40% of the population is deficient all winter, but only 25% through the summer. I bet quite a bunch of the billion people who are deficient are in latitudes where even on clear days in the winter, there's just not enough UVB for the very limited amount of time most people spend outside and the necessity of keeping maximum skin heavily covered.

  4. You can get almost all of that with prescription or otc meds/vitamins too. VitD helps with pretty much everything.

  5. My husband used to work third shift. His levels were too low, so the doctor put him on a vitamin D prescription. I guess that's common for third shift workers.

    Thanks for the great video!

  6. As an Irish person I would like to ask, what is this "Sun" you speak of? Sincerely, a nation with a combined Vitamin D intake of 3micrograms a year.

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