This topic has become one of the most debated areas of infant nutrition in the past few years. The optimal duration of exclusive breastfeeding is often equated with the optimal age for introduc- tion of solid foods. However, because CFs are defined by the WHO as any fluid or food other than breast milk, breast milk substitutes are regarded as CFs, and formula-fed infants are deemed to have received CF from the point at which they receive formula. Current WHO recommendations focusing on the intro- duction of CF in the context of the optimal duration of exclusive breastfeeding are therefore difficult to apply to formula-fed in- fants, yet this group constitutes a significant proportion of healthy term infants in many industrialized countries. The debate has become highly politicized. Inthisreview,wefirstdiscusstheavailablescientificevidence relevant to the question of whether exclusive breastfeeding for 6 mo results in benefits to mother and infant compared with exclusive breastfeeding for between 4 and 6 mo. We will also discuss available data relating to the situation in formula-fed infants.Wewillthenputthisinthecontextofthepoliticsofinfant feeding and the development of public health policy. THE SCIENCE Duration of exclusive breastfeeding and infant outcome Before 2001, the WHO recommended that infants be exclu- sively breastfed for 4–6 mo before the introduction of CF (2). Limited evidence from a prospective study in Dundee (7) sug- gested that the introduction of solid foods before 12 wk was associated with increased respiratory symptoms and greater fat- ness at 7 y of age, and 4 mo had been generally adopted as the earliest recommended age for introducing solid foods in most countries. The longstanding debate over the optimal duration of exclusive breastfeeding has centered on the so called “wean- ling’s dilemma” in developing countries: “the choice between the known protective effect of exclusive breastfeeding against infectious morbidity and the (theoretical) insufficiency of breast milk alone to satisfy the infant’s energy and micronutrient re- quirementsbeyond4moofage.”Toassesstheissue,asystematic review commissioned by the WHO was undertaken by Kramer and Kakuma (5) and subsequently published (8). The aim of the review was to consider whether mother and infant outcomes differed with exclusive breastfeeding for a minimum of 4 mo compared with 6 mo. The authors identified 20 studies compar- ing exclusive breastfeeding for 6 mo versus 3–4 mo. Only 2 studies were randomized intervention trials of different exclu- sive breastfeeding recommendations, both of which were con- ducted in a developing world setting (Honduras). All the trials from the developed world were observational. The authors made the following statements: “Neither the trials nor the observational studies suggest that infants . . . exclusively breastfed for 6 months show deficits in weight or length gain, although larger sample sizes would be required to rule out small increases in the risk of undernutrition.”
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- Fall '18