Vitamin D Defiency Linked to Allergies

There is hardly any "nutrient" (actually, vitamin D is rather a hormone, cf. Normann. 2008) that is so frequently investigated in contemporary nutrition and medical science as vitamin D. No wonder that almost every day studies suggest new beneficial effects of vitamin D on whatever medical condition you might imagine. The hypothesis of Vassallo and Carmargo, which is available online since 10 July 2010, is yet particularly interesting (Vasallo & Carmargo. 2010). The scientists propose

a “multiple-hit” model in which VDD [vitamin D deficiency] in a developmentally critical period increases susceptibility to colonization with abnormal intestinal microbial flora and gastrointestinal infections, contributing to abnormal intestinal barrier permeability and excess and inappropriate exposure of the immune system to dietary allergens. A compounding effect (and additional “hit”) of VDD is the promotion of a pro-sensitization immune imbalance that might compromise immunologic tolerance and contribute to FA. 

While this is only a model based on epidemiological studies, it is not without appeal. The main idea of the way vitamin D deficiency in early childhood virtually triggers an abnormal immune reaction is visualized in the following diagram (Vasallo & Carmargo. 2010. Fig 1)

So, in case you have a food allergy, go and ask your parents if you got sufficient amounts of sun exposure in your childhood or if they trusted in dermatological advice and tared you with sun-screen ;-)

If you want more information on the relation of vitamin D and (gut-)bacteria, have a look at Jun Sun's study (Sun. 2010) on the influence of vitamin D on the mucosal immune function.