For the better half
of the last century we have been told that the sun is our enemy. It gives us
skin cancer and that the smartest thing we could do was slather on thick layers
of sunscreen, wear a hat, and avoid sunburn. Unfortunately, as often happens in
our society, the pendulum now seems to have swung too far. Research definitely
tells us that sunburn is a bad bad thing. Even just one severe sunburn in
childhood can raise your risks of developing skin cancer as an adult by a
significant amount. But in our "go big or go home" rush to avoid the
sun we have inadvertently caused most of us to become vitamin D deficient.
You have probably
heard that we get vitamin D from the sun. Actually, it's a little more
complicated than that. Vitamin D starts as a molecule called
7-dehydrocholesterol (yes, it's based on that same cholesterol you hear all the
hype about). When 7-dehydrocholesterol gets into the blood vessels just under
your skin, and you happen to be out in the sun, the UV rays trigger a reaction
to produce cholecalciferol (coal-aay-cal-sif-fur-awl). This reaction takes
about 10 minutes to really get underway and a whole day's worth of vitamin D
can be produced in about 15-20 minutes of moderate sun exposure (this rate
varies based on skin type- faster for lighter skin, longer for darker), but
after too long in the sun your body does a very smart thing. Vitamin D in high
doses can be toxic so your body naturally starts limiting the reaction. This
means that more than 20 minutes is no longer beneficial in raising your vitamin
levels and can actually start destroying more than is being made. When you get
tan you make this reaction take longer by absorbing more of the light in higher
layers of your skin with the pigment melanin. So tanning (among other things)
is your body's natural way of protecting you from too much vitamin D if you are
someone who spends a lot of time in the sun. For most of us in the US it would
be easy to get our daily allotment of Vitamin D from the sun during the summer,
but in the winter things get a little more tricky. Not only are the days super
short, but if you live above about the 30th parallel (which includes most of
the US except Southern Florida and Hawaii) the sun doesn't even get high enough
in the sky during the winter to penetrate the atmosphere with enough strength
to trigger the reaction in the skin. So even if you live in a sunny area and
get out there naked in the freezing cold you sadly won't be producing enough
Vitamin D to qualify for a day's allotment.
So back to our story
of how your body actually makes Vitamin D. After the sun hits your skin and
makes cholecalciferol it then travels to your liver where another reaction
happens which changes it ever so slightly into a molecule called (boringly)
25-hydroxycholecalciferol. This then goes to the kidney where it undergoes yet
another change to become 1,25-dihydroxycholecalciferol. Woohoo! We made it to
the active form of the vitamin! This form only lasts approximately 2-4 hours in
circulation before it begins to break down and you have to start the process
all over. As you can imagine, with this kind of complicated path there are a
whole host of things that can go wrong! So besides not getting enough sun,
people can be low on vitamin D if they are missing any of the pieces of this
puzzle.
The primary function
that has been conventionally assigned to vitamin D is in bone formation. You
need proper amounts of Vitamin D in order to even absorb, let alone use calcium
and all the other fabulous bone building minerals. Vitamin D actually turns on
a gene which makes protein in your gut that binds to calcium to allow your body
to absorb it. Vitamin D has also been shown to protect against cavities (for
some of the same great reasons why it's so good for your bones). In fact, in
one study looking at over 3000 children from 1920-1980 researchers found a 50%
reduction in cavities in the kids with adequate Vitamin D.
For thousands of
years people in colder latitudes have eaten traditional foods that supply
Vitamin D during the cold winter months. Vitamin D is a fat soluble vitamin
which means.... surprise... that you find it in fats! Cod liver oil, lard,
whale fat, dairy, meat (not lean and
often organ in nature) all these yummy (?) favorites are great
traditional sources of Vitamin D. If you've read my fats blog then you'll know
how fabulous fat soluble vitamins are, and Vitamin D is no exception! Among
other things it acts as an anti-oxidant (yes, just like blueberries) and helps
to protect your tissues from those nasty free radicals. It is also considered
a "prohormone" which then gets
converted into... you guessed it.. a hormone! Researchers have found vitamin D
receptors on virtually all of the body's cells. You wouldn't expect to see that
many receptors if it wasn't a pretty important thing! You don't have to look
far to see what happens when your body lacks Vitamin D. The disease rickets,
where your bones fail to form normally, is the manifestation of a severe
Vitamin D deficiency, but Vitamin D deficiency has been associated with a host
of other diseases like multiple sclerosis (MS), diabetes type I (the autoimmune
version), and the biggie: cancer. Not surprisingly, 84% of patients who go to
the Cancer Treatment Centers of America are deficient in Vitamin D.
Like I said above,
we know that severe sunburn can increase your risk of skin cancer. In fact, sun
exposure in general increases your risk of skin cancer simply because those
same UV rays that convert the vitamin D also can hit things like your DNA and trigger
mutations which then lead to cancer. However, medicine is now starting to find
out how much protection the sun gives us from cancer via..... Vitamin D! Among
the cancers that Vitamin D has been shown to protect against: breast, prostate,
ovarian, colon... the list goes on.... and these are not minor cancers! These
are the biggies that require intense treatment and often come back again and
again. Skin cancer, on the other hand is easily treated by removal (duh, skin
is a lot easier to reach than your ovary) and is much more sensitive to
conventional cancer treatments (you can see it, therefore radiation can too).
Plus you can easily observer skin cancer and therefore it is much more
frequently found in routine screenings or by the person themselves and is
caught at earlier stages (which means it's easier to treat). These differences
in cancer types and treatability are significant and have everything to do with
figuring out the cost-benefit ratio for sun exposure. One recent study
concluded that the protection that Vitamin D gave against some of those nasty
internal cancers listed above far outweighed the related increased risk of skin
cancer from moderate sun exposure (not counting those nasty burns)! Let me say
that again because I know it took me re-reading it a few times before it sunk
in. With moderate sun exposure, your risks of all sorts of nasty internal
cancers goes way down and your risk of skin cancer only rises slightly. Wow!
Ahhhh... this is making me crave a little sunshine... too bad it's midnight in
Portland!
So how does Vitamin
D do all this cancer magic? Does anyone know? Yes! There have been multiple
studies looking at the so called "mechanism of action" of this
fabulous vitamin and it largely has to do with it's hormonal function (remember
I told you it was a hormone). Not only does it turn on the genes that cancer
turns off (mainly those that stop the cell from self-destructing when it
realizes things have gone awry), it also turns on anti-cancer genes
(specifically one called p53). Vitamin D also helps to keep your whole cell
cycle functioning properly. This is the
grow-->divide-->grow-->divide....die cycle of your cells. If this
malfunctions and things start to grow, and grow, and GROW you get tumors, so
keeping the cycle turning properly is very important. Vitamin D also has that
great little quality of being an antioxidant like I mentioned above and helps
to knock out nasty free-radicals in fatty tissues. Despite your thoughts about
your belly fat not mattering if the free radicals invade, you do actually have
some very important fatty tissue like the insulation around your nerves (called
a myelin sheath), oh... and this little old thing called your brain! If free
radicals get out of control (you mean get radical?) they can cause widespread
destruction of your DNA which... you guessed it, leads to cancer! So keeping
them in check is definitely a good idea.
Oh yeah! Vitamin D
also helps to regulate the production of a protein in your body called
cathelicidin. This protein is part of your body's innate immune system which is
the first part of your immune system to get activated any time you have an
infection. It helps to "nip it in the bud" as they say. Having
adequate Vitamin D helps ensure that your body is ready and armed to fight the
bugs, be they bacteria or be they viral.
So, in summary:
Vitamin D is made beginning with a reaction triggered by the sun. It is
naturally found in fat (and is commonly supplemented into dairy and other
foods) and meat to some degree. It has some very important functions in your
body (remember the receptor is found on virtually every cell in your body!) and
protects you against all sorts of nasty cancers, autoimmune diseases, helps
support your bones and teeth, and helps your immune system be ready to fight.
You cannot get adequate vitamin D in the winter months in the US (unless you
live in Florida or Hawaii- call me I need a sunny vacation!) and
supplementation is generally recommended (always good to get your values
checked to see how much is needed). The current recommended daily allowance was
raised in 2010 to 600 IU for pretty much everyone (special rates for those
under 1 and over 70). Since it's winter up here in Oregon and trying to snow I
will be including my vitamin D in my regimen today and every day until the sun
comes back in the spring.... ahhh.... daydreams of sun.... and Vitamin D!
One last note! I
forgot to talk about D2 vs D3. Vitamin D2 is a molecule called
ergocholecalciferol which your body can then convert into cholecalciferol, but
only does so at about 33% efficiency, so it's considered 1/3 as bioactive as D3
which is straight cholecalciferol ready to go to your liver. D2 is often the
form that will be naturally occurring in dairy products as it is made when hay
is left to dry in the sun, then the cows eat the hay, and magic! Vitamin D
enhanced dairy! The downside, other than the poor bioavailability is that it is
much easier to build up toxic levels of supplemented vitamin D2, hence why you
rarely see it marketed as a supplement any more.
Here are a couple
references from which I pulled some of this information:
The Huffington Post (huffingtonpost.com) - Vitamin D Might Protect Against Tooth
Decay: Study -By
Annie Hauser - (Friday, December 07, 2012) -
The Wall Street Journal (wsj.com) - Multiple Sclerosis Linked to Vitamin
D Levels, Study Says -By Jennifer Corbett Dooren
- (Monday, November 19, 2012)
Vit. D
and Diabetes type I
Vitamin
D and Cancer
I also included
information I learned last summer in my Integrative Oncology Research Course
and the basic biochem came right out of my biochem lecture on Vitamins from
last year.
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