December 17, 2009 — Late introduction of solid foods into the infant diet is associated with an increased risk for allergic sensitization to food and inhalant allergens at age 5 years, according to the results of a prospective, birth cohort study reported online in the December 7 issue of Pediatrics.
"The recommendation of exclusive breastfeeding for the first 6 months for the prevention of allergic diseases may lack strong scientific evidence," write Bright I. Nwaru, MPhil, MSc, from University of Tampere in Tampere, Finland, and colleagues. "Conversely, increased risk for atopic dermatitis, eczema, and allergic sensitization (with or without symptoms) has been associated with delayed introduction of egg, milk, cereals, and other solids....In the present study, we aimed to assess the association between age at the introduction of different solid foods during the first year of life and food and inhalant allergic sensitizations in a cohort of 5-year-old children with HLA [human leukocyte antigen]-conferred susceptibility to type 1 diabetes, taking into account reverse causality."
The investigators analyzed data regarding breast-feeding, age when solid foods were introduced, and allergen-specific immunoglobulin E (IgE) levels at 5 years from 994 children with HLA-conferred susceptibility to type 1 diabetes mellitus who were enrolled in the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) nutrition study. Logistic regression allowed analysis of the association between age at the introduction of solid foods and allergic sensitization.
Median duration of exclusive breast-feeding was 1.8 months (range, 0 -10 months). Late dietary introduction of potatoes (> 4 months), oats (> 5 months), rye (> 7 months), wheat (> 6 months), meat (> 5.5 months), fish (> 8.2 months), and eggs (> 10.5 months) was directly and significantly associated with sensitization to food allergens, after adjustment for potential confounders.
Late introduction of potatoes, rye, meat, and fish was significantly associated with sensitization to any inhalant allergen.
Eggs, oats, and wheat were the most important foods related to sensitization to food allergens, in models that included all solid foods that were significantly related to the endpoints. For sensitization to inhalant allergens, potatoes and fish were the most important foods. When parental allergic rhinitis and asthma were considered, the investigators found no evidence of reverse causality.
"Late introduction of solid foods was associated with increased risk of allergic sensitization to food and inhalant allergens," the study authors write. "Our observations in the present study are in accordance with reports showing that delayed introduction of solid foods may not prevent the development of allergic diseases in children."
Limitations of this study include short median duration of exclusive breast-feeding in the study population and selection of birth cohort based on HLA-conferred susceptibility to type 1 diabetes, limiting generalizability. In addition, the endpoints were sensitization against food and inhalant allergens, so these results may not indicate the effects of timing of the introduction of solid foods on actual asthma, atopic eczema, or other clinical allergic outcomes. The number of these endpoints was small, resulting in insufficient statistical power for any meaningful analysis.
"Extended follow-up monitoring of our study cohort will clarify whether our present observations can be translated into clinical allergic outcomes," the study authors conclude. "These findings challenge the current recommendations regarding infant feeding for the prevention of allergic diseases."
Pediatrics. Published online December 7, 2009. Abstract
Although exclusive breast-feeding for the first 6 months of life and introduction of solid foods thereafter are currently recommended to prevent allergic diseases in children, evidence to support this advice is limited. Among the few studies that have attempted to address this issue, the results are inconsistent.
Reverse causality must also be considered in assessing the relationship between the timing of the introduction of solid foods and the development of allergic diseases. Families in which there is positive family history of allergic diseases, or in whom infants have early signs of allergy, may delay introducing solids into the infant diet, thereby masking any temporal relationship between the introduction of solid foods and the development of allergies.
Ages at which dietary introduction was considered to be late was older than 4 months for potatoes, older than 5 months for oats, older than 7 months for rye, older than 6months for wheat, older than 5.5 months for meat, older than 8.2 months for fish, and older than 10.5 months for eggs.