D is for Defense! Vitamin D and the Immune System

posted on October 23, 2011

It`s that time of year again; cold and flu season...and the kids are coming home with more than homework.  An optimal immune system is your best defence against any bug and recent research is highlighting a key role for Vitamin D. 

Vitamin D has long been known as a regulator of calcium and, thus, is an important vitamin for bone health.  But vitamin D has far reaching benefits including boosting your immune function.  New research suggests that Vitamin D directly interacts with multiple immune cell types to modulate their function in an immune response1-2.  For our T (killer) cells, essential in the fight against serious infections, Vitamin D is responsible for changing them from dormant to activated fighter cells.  This confirms why those lacking in vitamin D face an increased risk of infectious disease and why supplementing is actually protective3.

Being that the main source of vitamin D is from sun exposure, deficiency is a very real issue for us Canadians.  It is during these cold and dark months that we get minimal sun exposure.  Even on sunny winter days, our skin exposure is inadequate to absorb enough D.  In 2010 Statistics Canada published results of a population-wide survey on Vitamin D status of Canadians.  It revealed that greater than half of Canadians do not have adequate levels known to prevent chronic diseases (like cancer) and 4% were at risk for serious deficiency syndromes such as rickets (causing serious bone deformities)4

Vitamin D is a fat-soluble vitamin.  This means that it can accumulate in your body so, although it is rare, overdosing is potentially an issue. 

So, what can you do?  Most adults are safe to supplement Vitamin D at a level of 500-1000IU per day. However, it is more important to find out your own Vitamin D status so you can supplement appropriately to obtain optimal levels.  The current recommended daily intake of 600IU will not replete a deficiency.  Sometimes short-term high dosing is necessary to get your body back on track. 

Talk to your Naturopath about getting your sunshine vitamin to boost your defenses.  They can provide Vitamin D testing and guide you on how to achieve adequate levels. 

  1. Bikle D. Vitamin D and the immune system: role in protection against bacterial infection.  Curr Opin Nephrol Hypertens. 2008 Jul;17(4):348-52.
  2. Baeke F, Takiishi T, Korf H, Gysemans C, Mathieu C. Vitamin D: modulator of the immune system. Curr Opin Pharmacol. 2010 Aug;10(4):482-96. Epub 2010 Apr 27.
  3. Urashima M, Segawa T, Okazaki M et al. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 Mar 10
  4. Langlois K, Greene-Finestone L, Little J, Hidiroglou N, & Whiting S. Vitamin D status of Canadians as measured in the 2007 to 2009 Canadian Health Measures Survey. StatsCan  Health Reports 2010:21(1)


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