What is the question?

• The question is: What is the relationship between shorter versus longer durations of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, and asthma?

What is the answer to the question?

• There is insufficient evidence to determine the relationship between shorter versus longer durations of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, and asthma throughout the lifespan. 

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? 

• The population of interest was generally healthy infants and toddlers (ages 0-24 months) who were in studies examining food allergies, allergic rhinitis, and atopic dermatitis throughout the lifespan and asthma from childhood through adulthood (ages 2 years and up).

What evidence was found? 

• This review includes 1 article, which was not enough evidence to draw any conclusions about the relationship between the duration of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, or asthma.

How up-to-date is this systematic review? 

• This review includes literature from 01/1980 to 03/2016.

Background

• This systematic review was conducted 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 examine the following question: What is the relationship between shorter versus longer durations of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, and asthma?
• This systematic review examines comparisons of infants who were fed human milk exclusively for shorter durations with infants who were fed human milk exclusively for longer durations prior to being introduced to infant formula. The question examines exclusive human milk feeding preceding the introduction of infant formula, only, to avoid overlap with another systematic review that examined the timing of the introduction of complementary foods and beverages and its relationship with food allergies, allergic rhinitis, atopic dermatitis, and asthma.
• Exclusive human milk feeding was defined as feeding human milk alone and not in combination with infant formula and/or complementary foods or beverages such as cow’s milk. This definition is inclusive of the World Health Organization definitions of exclusive and predominant breastfeeding, which permit limited quantities of (a) drops or syrups containing vitamins, minerals, or medicines, (b) water and water-based drinks such as sweetened water and teas, (c) fruit juice, (d) oral rehydration salts solution, and (e) ritual fluids . Human milk was defined as mother’s own milk provided at the breast (i.e., nursing) or expressed and fed fresh or after refrigeration or freezing. Donor milk (e.g., banked milk) was not examined in this review. 
• This systematic review examines available evidence related to food allergies, allergic rhinitis, and atopic dermatitis from birth through adulthood and asthma from childhood through adulthood (outcomes prior to childhood may represent transient recurrent wheeze).

Conclusion Statement and Grade

• There is insufficient evidence to determine the relationship between shorter versus longer durations of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, and asthma throughout the lifespan. 
  
  Grade: Grade Not Assignable

Methods 

• The systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review in collaboration with a Technical Expert Collaborative.
• A single literature search was conducted to identify literature for several related systematic reviews that examined infant milk-feeding practices and different outcomes. The search was conducted in CINAHL, Cochrane, Embase, and PubMed, and used a search date range of January 1980 to March 2016. A manual search was done to identify articles that may not have been included in the electronic databases searched. 
• Articles were screened independently by 2 NESR analysts to determine which articles met predetermined criteria for inclusion.
• Data from the included article were extracted, risks of bias were assessed, and both were checked for accuracy. 
• 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.

Summary of Evidence 

• This review includes 1 article, which provided insufficient evidence to draw any conclusions about the relationship between the duration of exclusive human milk feeding prior to the introduction of infant formula and food allergies, allergic rhinitis, atopic dermatitis, or asthma.
• There may be a large degree of overlap between current literature examining the duration of exclusive human milk feeding (which may terminate with complementary feeding) and the timing of the introduction of complementary foods and beverages (which may immediately follow a period of exclusive human milk feeding). Yet, the degree of overlap is difficult to ascertain; infant-feeding research does not often specify whether exclusive human milk feeding is followed by complementary feeding or formula feeding or both, and complementary feeding research does not often specify whether complementary foods and beverages are introduced to infants fed human milk exclusively or fed infant formula in some amount. It would be beneficial for future researchers to be mindful about this potential ambiguity when designing and conducting research about the duration of exclusive human milk feeding or the timing of the introduction of complementary foods and beverages, and strive to help clarify any unique contributions of each of the two feeding practices on atopic disease and other outcomes.