What is the question?

• The question is: What is the relationship between the timing of introduction of complementary foods and beverages and food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis?

What is the answer to the question?

• Moderate evidence suggests that there is no relationship between the age at which complementary feeding first begins and risk of developing food allergy, atopic dermatitis/eczema, or asthma during childhood.
• There is insufficient evidence to determine the relationship between the age at which complementary foods or beverages are first introduced and risk of developing allergic rhinitis during childhood. 

Why was this question asked? 

• This important public health question was identified and prioritized as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.

How was this question answered? 

• A team of Nutrition Evidence Systematic Review staff conducted a systematic review in collaboration with a group of experts called a Technical Expert Collaborative

What is the population of interest? 

• Generally healthy infants and toddlers who were fed complementary foods and beverages from ages 0-24 months and had food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis examined through 18 years of age.

What evidence was found? 

• This review includes 31 studies.
• These studies looked at the age when a complementary food or beverage was first introduced to the infant were first introduced and food allergy, atopic dermatitis/eczema, asthma, or allergic rhinitis. 
• Complementary foods and beverages are foods and beverages other than human milk or infant formula provided to an infant or young child.
• Most evidence reported no relationship between age of complementary food or beverage introduction and outcomes.
• There are limitations in the evidence as follows: use of less reliable methods to measure outcomes, only a few studies were done for some types of foods and/or outcomes, and other factors that may have had an impact on results were not always accounted for.

How up-to-date is this systematic review? 

• This review includes literature from 01/1980 to 02/2017.

Background

• Complementary feeding is the process that starts when human milk or infant formula is complemented by other foods and beverages, beginning during infancy and typically continuing to 24 months of age.
• This systematic review was conducted by a team of Nutrition Evidence Systematic Review (NESR) staff as part of the U.S. Department of Agriculture and Department of Health and Human Services Pregnancy and Birth to 24 Months Project.
• The goal of this systematic review was to answer the following research question: What is the relationship between timing of introduction of complementary foods/beverages and food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis?

Conclusion Statement and Grade

• Moderate evidence suggests that there is no relationship between the age at which complementary feeding first begins and risk of developing food allergy, atopic dermatitis/eczema, or asthma during childhood. 
• There is insufficient evidence to determine the relationship between the age at which complementary foods or beverages are first introduced and risk of developing allergic rhinitis during childhood.
  
  Grade: Moderate – Food allergy, atopic dermatitis/eczema, asthma; Grade Not Assignable – Allergic rhinitis

Methods 

• This systematic review was conducted by a team of staff from NESR in collaboration with a Technical Expert Collaborative. 
• A literature search was conducted using 4 databases (CINAHL, Cochrane, Embase, and PubMed) to identify articles published from January 1980 to February 2017 that examined the age when complementary foods and beverages (CFB) were first introduced and food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis. CFB were defined as foods and beverages other than human milk or infant formula provided to an infant or young child. Outcomes included incidence and prevalence of food allergy, atopic dermatitis/eczema, asthma, and allergic rhinitis. A manual search was done to identify articles that may not have been included in the electronic databases searched. Articles were screened in a dual manner, independently by 2 NESR analysts, to determine which articles met predetermined criteria for inclusion.
• Data from each included article were extracted, risk of bias was assessed. The body of evidence was qualitatively synthesized, a conclusion statement was developed and the strength of the evidence (grade) was assessed using pre-established criteria including evaluation of the internal validity/risk of bias, adequacy, consistency, impact, and generalizability of available evidence. Research recommendations were identified.

Summary of Evidence

• Thirty-one observational studies are included in this systematic review, having examined the relationship between the age of first introduction to a CFB and risk of food allergies, atopic dermatitis/eczema, asthma, and allergic rhinitis occurring during childhood through 18 years of age. 
  • The studies included in this review examined the timing of introduction to CFB, or the age at which infants were first introduced to any foods or beverages other than human milk or infant formula were first introduced to an infant. (Note: Studies that examined the timing of introduction of specific types of CFB, including common allergenic foods, such as peanuts, eggs, and fish, are addressed in a separate review).
  • These studies did not specify what food or beverage was first introduced. However, highly allergenic foods are not typically the first CFB introduced into an infant’s diet; therefore, it is likely that the studies in this body of evidence reflect the first introduction of cereals, fruits, and vegetables.
  • Nine studies examined risk of food allergy, 20 studies examined risk of eczema or atopic dermatitis, eight studies examined risk of asthma, and four studies examined risk of allergic rhinitis. 
• Most evidence reported no significant associations between age of CFB introduction and risk of food allergy. While some evidence suggested that earlier first introduction of CFB may be associated with increased risk of developing food allergy, confidence in the results was restricted by methodological limitations.
• The ability to draw stronger conclusions about the relationship between the timing of first introduction to CFB and the risk of atopic disease is due to several limitations:
  • Use of non-validated or unreliable measures to assess risk of atopic disease (e.g., parent report of a physician diagnosis or the child’s symptoms), and assessment of outcomes later in childhood (through 10 years of age), when some atopic diseases, such as eczema, may have already resolved, or very early in childhood (3-4 months), before some atopic diseases may have occurred.
  • Lack of adjustment for key confounders such as consumption of human milk and/or human milk substitutes (e.g., cow’s milk formula, hydrolyzed infant formula, or fluid cow’s milk), parental smoking, and exposure to household pets
• Potential for reverse causality due to baseline atopic disease risk status impacting both the timing and types and amounts of CFB introduced, and risk of developing atopic disease.