PURPOSE OF THE STUDY.
In light of epidemiologic studies that show increased prevalence of food allergy in populations who reside farther from the equator, investigators sought to determine the association between vitamin D and food allergy.
From 2007 to August 2011, a total of 7134 infants between 11 and 15 months of age (inclusive) were approached during immunization visits at 120 locations throughout Australia.
A total of 5120 infants underwent skin-prick testing (SPT) to peanut, egg, sesame, and cow’s milk or shrimp. Infants with a detectable wheal ≥1 mm as well as a random sample of infants with negative SPT were referred to a food allergy center for oral food challenge and repeat SPT using an extended panel of foods. Infants were deemed food allergic if they had both positive food challenge by objective criteria and an SPT wheal size ≥2 mm or a specific IgE ≥0.35 kUA/L. For foods on the extended spectrum SPT, a wheal size ≥8 mm was considered indicative of food allergy. Infants were labeled food-sensitized tolerant if they had negative oral food challenge despite a wheal size ≥2 mm or a specific IgE ≥0.35 kUA/L. Blood samples were obtained for measurement of 25-hydroxyvitamin D3 levels and were seasonally adjusted. Vitamin D deficiency was defined as a serum level ≤25 nmol/L (<10 ng/mL), insufficiency as 25 to 50 nmol/L (10–20 ng/mL), and sufficiency as >50 nmol/L (equivalent to 20 ng/mL). Associations between vitamin D and food allergy were analyzed by using multiple logistic regression, adjusting for potential risk factors and confounding variables.
A total of 928 (85%) of the infants with positive SPT test and 197 (20%) controls visited the food allergy referral center. Complete data were available for a total of 481 infants. Among those classified as food sensitized (361), infants with vitamin D insufficiency were 3 times more likely to have food allergy than to be food-sensitized tolerant. For infants of Australian-born parents (271), vitamin D–insufficient infants were 3 times more likely to have any food allergy (P = .032), 10 times more likely to have multiple food allergies (≥2) (P = .014), 11 times more likely to have peanut allergy (P = .006), and 3 times more likely to have egg allergy (P = .025). The relationship between vitamin D status and food allergy was not significant for infants of foreign-born parents. Vitamin D insufficiency did not increase odds of the infant having eczema.
This is the first study to demonstrate an association between challenge-proven food allergy and vitamin D levels at 12 months, particularly among infants with allergic sensitization.
This study provides supporting evidence for the hypothesis that vitamin D insufficiency is a risk factor for development of food allergy. It adds to the growing body of literature suggesting that vitamin D modifies risk of allergic diseases such as asthma, allergic rhinitis, and food allergy, although, notably, the investigators did not find an association between vitamin D levels and eczema. Further study is needed to determine whether correction of vitamin D insufficiency would result in decreased food allergy and increased tolerance among those sensitized.
- Copyright © 2013 by the American Academy of Pediatrics