Here Comes the Sun: Vitamin D, Allergies, and Asthma

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Every few years there’s a hot new allergy topic that’s going to explain and/or cure the growing problem of allergies.  Several years ago it was the so-called Hygiene Hypothesis which basically said that fewer childhood infections meant more allergies.  It made some sense immunologically, too, but results of studies looking at it have been mixed.  The new hot topic is Vitamin D deficiency.  Let’s take a look, shall we?

Back in the day, I did my internal medicine training at the University of Virginia.  UVa is known for several things: mostly for being Mr. Jefferson’s university, but also for being Ralph Samson’s alma mater and for being the home of the finest bagel shop on the planet, Bodo’s Bagels.  In the allergy world, it is known as the home of Dr. Thomas A.E. Platts-Mills, a leader in our field, and the father of dust mite allergy.  I had the opportunity to spend some time in residency working with Dr. Platts-Mills and he is a brilliant man.  Like all truly brilliant people, however, he’s thinking on a different plane from the rest of us and some of his ideas seemed a bit out there.  That, coupled with his inscrutable British demeanor often left me wondering whether I was being mocked or instructed, laughed at or laughed with.  In any event, one of Dr. Platts-Mills pet peeves was television.  The man could not stand TV and one of the first tings he would tell parents of allergic children was to throw away their TV and get their kids outside.  If the growing body of literature on Vitamin D is correct, he was probably right.

Humans get Vitamin D from 2 sources: sunlight and diet.  Historically, over 90% of our Vitamin D has come from exposure to sunlight which, in simplest terms, kick starts the reaction that leads to Vitamin D production.  Vitamin D is relatively scarce in our natural diet, but is added many common foods like milk and sugary breakfast cereals, so we now obtain a higher percentage through diet.  Even with supplementation, however, as we spend more time indoors watching Spongebob, playing on the Wii or blogging, our natural source for Vitamin D is waning.  Recent research suggests that around 1 in 10 kids is Vitamin D deficient and that an additional 60% of kids may have Vitamin D insufficiency!

So how does this relate to allergies and asthma?  Most studies looking at this are merely observational  and therefore show correlation, but not causation.  That is, low Vitamin D might be a marker for allergies and asthma, but not a root cause.  When you look at Vitamin D’s effects on the immune system and on other cells in the body, there is enough there to make a reasonable hypothesis that Vitamin D deficiency may be a contributing factor to allergies and asthma and that Vitamin D supplementation could be a potential treatment for people with deficient or insufficient levels.

Of course, you could always just throw away your TV and get outside……..

Important note on Vitamin D Supplementation: Vitamin D is one of the fat soluble vitamins, along with A, E, and K.  This means that your body stores it up rather than just getting rid of it through the urine, like it does with Vitamins B’s and C.  Thus, over time, if you take too much of a Vitamin D supplement, you can develop Vitamin D toxicity.  If you do use Vitamin D supplements, be sure to follow the recommended doses.

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