Vitamin D deficiency may be a factor in development of allergies

THE QUESTION Too little Vitamin D can lead to bone problems and diseases. Might it also play a role in the development of allergies?

THIS STUDY analyzed data on 6,590 people, roughly half of them 21 years of age and younger and half older. The group was deemed representative of the U.S. population. Vitamin D levels were determined by blood tests, as was sensitivity to 17 common allergens. Among the youths, food and environmental allergies were greater in those with lower levels of Vitamin D. Young people deficient in Vitamin D were about twice as likely as those with higher levels of the nutrient to have peanut or ragweed allergies and nearly five times as likely to be allergic to oak. Allergies to dogs, cockroaches, shrimp, ryegrass, Bermuda grass, birch, certain fungi and thistle also were more common in youths with the lowest Vitamin D levels. In adults, however, no link was found between Vitamin D levels and allergen sensitivity.

WHO MAY BE AFFECTED? People with low levels of Vitamin D. For most people, exposure to 15 minutes of sunshine three times a week enables the body to produce a sufficient amount of Vitamin D. It's also available in some foods (dairy products and fortified cereals, for example) and in supplements. The amount needed varies by age, with current guidelines suggesting that people need 600 international units (IU) daily up to age 70 and 800 IU thereafter. Some experts, though, say those amounts are not sufficient.

CAVEATS The study did not test whether increasing Vitamin D levels through supplements or other means would affect allergy symptoms, nor did it determine why the association found in children was not replicated among the adults.

FIND THIS STUDY Feb. 17 online issue of the Journal of Allergy and Clinical Immunology (www.jacionline.org/inpress).

LEARN MORE ABOUT Vitamin D at www.hsph.harvard.edu/nutritionsource and www.ods.od.nih.gov.

- Linda Searing

The research described in Quick Study comes from credible, peer-reviewed journals. Nonetheless, conclusive evidence about a treatment's effectiveness is rarely found in a single study. Anyone considering changing or beginning treatment of any kind should consult with a physician.

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