Low Vitamin D Status Could Boost Children's Allergy Risk
Lee Swanson Research Update
Lead researcher Michal Melamed, MD, MHS, assistant professor of medicine and epidemiology and population health said: "It is one link in the puzzle, or a first step. It is not the definitive study to show this link but one of the first large studies that shows that this association exists. There are many other reasons to make sure that children and adolescents receive the daily recommended intake of vitamin D—including, importantly, bone health."
Melamed and her team examined serum vitamin D levels in blood collected from a nationally representative sample of more than 3,100 children and adolescents and 3,400 adults in 2005-2006. The study defined children and adolescents as participants aged one to 21.
The samples were derived from the National Health and Nutrition Examination Survey (NHANES), a program of studies designed to assess the health and nutritional status of adults and children across the U.S. One of the blood tests assessed was sensitivity to 17 different allergens by measuring levels of Immunoglobulin E (IgE), a protein made when the immune system responds to allergens.
No link was found between vitamin D levels and allergies in adults. But, for children and adolescents, low vitamin D levels could be linked to sensitivity to 11 of the 17 allergens tested. Those included both environmental allergens, such as ragweed, oak, dog, and cockroach, and food allergens such as peanuts.
Children who had vitamin D deficiency—defined as fewer than 15 nanograms of vitamin D per milliliter of blood—were 2.4 times as likely to have a peanut allergy than were children with sufficient levels of vitamin D—defined as more than 30 nanograms of vitamin D per milliliter of blood.
"The latest dietary recommendations calling for children to take in 600 IU of vitamin D daily should keep them from becoming vitamin D deficient," Melamed confirmed.
The researchers are unsure why vitamin D could enhance children’s susceptibility to developing allergies but not for adults. One reason may be that most allergic sensitization may happen in childhood.
"When we measure an adult’s vitamin D level it probably is not reflective of what that person’s vitamin D level was when they were a child and became sensitized. There may also be different mechanisms for allergic sensitization in adults and children," said Melamed.
Melamed’s study measured vitamin D and the IgE levels at the same time. "The next study should measure vitamin D levels at a baseline time and then follow high-risk kids for the development of allergies," she said. "Eventually, a randomized, placebo-controlled clinical trial in high-risk individuals will provide definitive evidence."
Journal of Allergy and Clinical Immunology Published online ahead of print
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March 2011