Unit 2: Health Effects of Complementary Feeding

The World Health Organization states that the introduction of complementary foods is necessary when

"breast milk (or infant formula) alone is no longer sufficient to meet the nutritional requirements of infants and therefore other foods and liquids are needed, along with breast milk.”
(WHO 2003)

On the basis of current evidence, both too early (< 12 to 17 weeks) and too late (>26 weeks) introduction of complementary foods, can have undesirable health consequences. Exclusive breastfeeding for about 6 months according to the WHO is a desirable goal, and complementary feeding should be introduced after the 17th week and no later than the 26th week while continuing to breastfeed as the child requests (Agostoni et al. 2008; Bührer et al. 2014; Koletzko et al. 2013; EFSA 2009; Fewtrell et al. 2017). During that period, complementary foods are intended to 'complement' ongoing breastfeeding and enable the transition from milk feeding to family foods (Przyrembel 2012).

The timing of the introduction of complementary foods varies amongst infants; however six months of exclusive breastfeeding is a desirable goal for most healthy term infants. Complementary foods are intended to 'complement' ongoing breastfeeding and enable the transition from milk feeding to family foods (Przyrembel 2012).

Breast feeding and complementary feeding can have short and long term effects on health. Possible short term health effects include growth (weight gain) and infections, and possible long term effects include obesity, atopic disease and diabetes mellitus. However, based on the current available evidence, it is difficult to determine the exact age when the introduction of complementary foods poses the highest or lowest risk on these health effects (Przyrembel 2012).

In contrast to the large literature on breast feeding, less attention up to today has been paid to the complementary feeding period and whether this period is associated with later health and development outcomes (Agostoni et al. 2008). The current knowledge on the health effects of the introduction of complementary foods is based mainly on observational studies, however, further research is needed (Przyrembel 2012). The following figure demonstrates the complexities and challenges of understanding the relationship between infant feeding and health outcomes.

On the basis of current evidence, both too early (< 12 to 17 weeks) and too late (>26 weeks) introduction of complementary foods, can have undesirable health consequences. Exclusive breastfeeding for about 6 months is a desirable goal, and complementary feeding should be introduced after the 17th week and no later than the 26th week while continuing to breastfeed as outlined in Unit 1 of this module (Agostoni et al. 2008).

Figure 1: Complexity and challenges of understanding the strength of relationship/causality between timing and outcomes. Too early or too late introduction, can have adverse health consequences/bear an increased risk of disease: theoretical 'window' (unshaded area) and current feeding practices (curves, shapes and percentages are approximate). Dotted curve = formula feeding, solid curve = liquids other than breast milk or formula.

Source: Przyrembel 2012, reprinted with permission of S. Karger AG, Basel