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 the Nutrition Evidence Systematic Review team 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 and beverages and micronutrient status?
Moderate evidence suggests that introducing complementary foods and beverages at 4 months of age compared to 6 months of age offers no long term advantages or disadvantages in terms of iron status among healthy, full-term infants who are breastfed, fed iron fortified formula, or both. (Grade: Moderate – Iron Status). There is not enough evidence to determine the relationship between timing of introduction of complementary foods and beverages and zinc, vitamin D, vitamin B12, folate, or fatty acid status. (Grade: Grade Not Assignable - Zinc, Vitamin D, Vitamin B12, Folate, and Fatty Acid Status).
The systematic review was conducted by a team of staff from the Nutrition Evidence Systematic Review 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 March 2016 that examined the age when complementary foods and beverages (CFB) were first introduced and micronutrient status. CFB were defined as foods and beverages other than human milk or infant formula provided to an infant or young child. Micronutrient status outcomes included iron, zinc, vitamin B12, folate, vitamin D, and/or folate status. 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, risks of bias were assessed, and both were checked for accuracy. 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.
Nine studies published from 1/1980 to 3/2016 met the inclusion criteria for this systematic review, with most studies examining the relationship between timing of introduction of CFB and iron status. Few studies examined zinc, vitamin D, vitamin B12, folate, and/or fatty acid status. The majority of studies reported no significant associations between timing of CFB introduction and micronutrient status. Additional factors that need to be considered in examining the relationship between the age at which CFB are introduced and micronutrient status include: birth weight, post-natal growth, type of feeding (breast, formula, or mixed feedings), iron stores at birth, and intake and absorption of iron from sources other than human milk, including types and amounts of CFB being consumed.
