Sunday, May 22, 2011

Vitamin D and Allergic Diseases

Low levels of vitamin D have been increasingly associated with the presence of an allergic disease (atopic dermatitis, allergic rhinitis, asthma) and obesity.  These observations have been noted in many studies.  The most recent I'd like to highlight is by Sharief S et al in the May 2011 issue of the Journal of Allergy and Clincial Immunology 2011; 127: 1295-1202.  The title is "Vitamin D level and food and environmental allergies in the United States: Results from the National Health and Nutrition Examination Survey 2005-2006".  Children, not adults, were found to be 2-3x more likely to have an allergic disease.  The nature of the association is unclear, meaning there is not sufficient proof yet that low vitamin D levels cause or contribute to development of allergic diseases.  The mechanism is unclear also.  The general hypothesis is that vitamin D some how interacts with the immune system and improves its normal functioning, leaving the person less likely to have abnormal immune functioning and so less allergic or autoimmune diseases.
So you can see where this is going.  Should we take more vitamin D to prevent or treat allergic diseases?  There is no definitive answer yet.  Researchers are working on this.

The same issue [Journal of Allergy and Clinical Immunology 2011; 127: 1294-6.] also had a study by Majak P et al entitled "Vitamin D supplementation in children may prevent asthma exacerbation triggered by acute respiratory infection".  The study gave one group a dose of vitamin D for children of 500 I.U., which is slightly more than the the Institute of Medicine's recommended daily dose of 400 I.U. The control group did not receive vitamin D.  They found, they state for the first time in the published literature, that vitamin D supplementation did significantly reduce the number of asthma exacerbations.  The study was very small, 48 subjects total, and will have to be repeated in multiple other studies, but it is a hopeful sign.

What's your Allergy Dude's take on all of this?  There have been a lot more studies and discussion that I have not highlighted here as of yet.  I am closer to the tipping point of recommending further vitamin D supplementation, but right now I am sticking with my recommendation for all of my patients to have a balanced, very low salt, low animal fat diet that should contain vitamins and minerals.  If people are unsure of the content, it would not hurt them to take a daily multivitamin.  This was also recommended by the Institute of Medicine to the U.S. and Canadian governments.

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