Vitamin D deficiency linked to allergies in kids

A new study reveals that children with low vitamin D levels are more likely to suffer from both food allergies and inhalant allergies.

Researchers found a link between allergies to ragweed, oak, dogs, cockroaches, shrimp and six other allergens and vitamin D deficiencies. There was a strong relationship to peanut allergy, one of the most common food allergies and one which causes significant problems for children due to hidden traces of peanut proteins in many foods.

In this large scale epidemiological study a team of American researchers analysed blood samples from 3,136 children and adolescents and 3,454 adults to look for any links between serum vitamin D levels and sensitivity to 17 different allergens. Confounding factors such as milk consumption, obesity and socio-ecomonic status, which could affect the results, were also taken into account. The results of the study are published in the Journal of Allergy and Clinical Immunology.

The researchers found that vitamin D deficiency in children and adolescents was associated with a higher risk of IgE-mediated sensitivity to 11 of the 17 allergens tested. The increased risk was of greatest significance for peanut, ragweed, and oak allergies. Interestingly, no association was found between vitamin D status and allergy risk in the adults tested.

For the purposes of the study those participants with a serum vitamin D (25(OH)D ) level of less than 15 nanograms per millilitre of blood were considered to be deficient.

Michal Melamed, Assistant Professor of Medicine and of Epidemiology and Population Health at Albert Einstein College of Medicine in New York, and one of the researchers on the study, was careful to note that the study is correlational and does not in itself prove that a deficiency of vitamin D causes childhood allergies.  It may be that there is another factor that increases a child's risk of both allergies and vitamin D deficiency, thus making them more likely to both occur in the same child. Further studies would be required that look at causation to confirm that vitamin D deficiency is a specific risk factor for allergies in children.

However, Melamed recommends that children consume sufficient amounts of vitamin D. "The latest [US] dietary recommendations calling for children to take in 600 IU of vitamin D daily should keep them from becoming vitamin D deficient," she said in a press release. 

A previous study reported that the number of people who visit hospital due to acute allergic reactions to food rises in the winter, the researchers said, suggesting a possible link to vitamin D. Vitamin D levels naturally drop during the winter months, particularly in very northerly latitudes, since sunlight is necessary for the production of the vitamin in the skin. 

It is well known that the production of vitamin D in the skin on exposure to sunlight is much more efficient at improving blood vitamin D status than dietary consumption so it may be that playing sports or taking part in other outdoor activities may benefit kids in more ways than simply burning excess calories.

Source: Sharief S Jariwala S Kumar J Muntner P Melamed M (2011) Vitamin D levels and food and environmental allergies in the United States: Results from the National Health and Nutrition Examination Survey 2005-2006 Journal of Allergy and Clinical Immunology DOI: 10.1016/j.jaci.2011.01.017