Delaying solid foods increased risk for allergies

Current recommendations favoring exclusive breast-feeding to prevent allergic sensitization during the first six months of an infant’s life may not be beneficial, findings suggested.

“Late introduction of solid foods was associated with increased risk of allergic sensitization to food and inhalant allergens,” the researchers wrote.

They assessed breast-feeding information, age at introduction of solid foods and allergen-specific immunoglobulin E levels at age 5 years in a prospective birth cohort that included 994 children with human leukocyte antigens–conferred susceptibility to type 1 diabetes. All participated in the Finnish Type 1 Diabetes Prediction and Prevention nutrition study.

At baseline, the researchers determined 17% of children had allergic sensitization to any food allergen, and 23% were sensitized to any inhalant allergen.

Using a backward, stepwise logistic regression analysis, the researchers found that delaying eggs, oat and wheat was most often associated with food allergy sensitization. Other related foods included potato, meat and fish. Similar trends for inhalant allergy sensitization were also observed, with delayed introduction of potato and fish leading the way for those types of allergies. Other foods implicated in inhalant sensitization included oats, rye and meat.

These trends remained after the researchers performed reverse causality analyses and adjusted for confounding factors including season of birth, delivery hospital, sex, number of siblings, parental asthma, parental allergic rhinitis, maternal age, maternal basic education, maternal smoking during pregnancy, mode of delivery, ponderal index and pets in the home during the first year of life.

“Although the advantages of breast milk as the optimal form of feeding for children in the first months of life cannot be overemphasized, the role of exclusive breast-feeding in the prevention of allergic diseases is not clear,” the researchers wrote.

Nwaru BI. Pediatrics. 2010;125:47-56.

PERSPECTIVE

This prospective cohort study attempts to determine if duration of exclusive breast-feeding and timing of solid food introduction influences allergic sensitization to food or pollen. Present recommendations from the American Academy of Pediatrics suggests a protective effect against development of certain allergic disease is associated with breast-feeding exclusively for a minimum of 4-6 months, and do not support delaying sold food introduction beyond 4 months.

The findings in this study do suggest a significant relationship between delayed introduction of egg, wheat, and oat, with increased risk of developing specific IgE against these foods at age 5.

Similarly, delayed introduction of potato and fish increased the risk of developing specific pollen sensitization at age 5. While the associations were statistically significant, the criteria used to determine allergic sensitization was set at a serum IgE level >0.35 kU/L (class I or higher). This is an exceptionally low cut-off point and may over-estimate the rate of sensitization, given that specific IgE levels between 0.35 kU/L and 0.70 kU/L are not considered indicative of a significant sensitization. Other factors, such as symptoms attributable to these foods in sensitized individuals, were not examined. This calls into question the relevance of the sensitization, which may not necessarily be indicative of having an actual allergy to that item.

Overall, while this study attempts to find a relationship between exclusive breast-feeding, timing of solid introduction, and the development of allergic sensitization, caution must be taken in interpreting the author’s conclusions due to the use of very low cut-offs to determine sensitization, and the absence of clinical correlation between the positive sensitization and symptoms of allergy.

— Matthew Greenhawt, MD,

Clinical Lecturer

Division of Allergy and Clinical Immunology

University of Michigan Medical School

University of Michigan Health Systems