Nutrient adequacy of exclusive breastfeeding for the term infant during the first six months of life
This review, which was prepared as part of the background documentation for a WHO expert consultation, evaluates the nutrient adequacy of exclusive breastfeeding for term infants during the first 6 months of life. Nutrient intakes provided by human milk are compared with infant nutrient requirements. To avoid circular arguments, biochemical and physiological methods, independent of human milk, are used to define these requirements.
The review focuses on human-milk nutrients, which may become growth limiting, and on nutrients for which there is a high prevalence of maternal dietary deficiency in some parts of the world; it assesses the adequacy of energy, protein, calcium, iron, zinc and vitamins A, B6 and D. This task is confounded by the fact that the physiological needs for vitamins A and D, iron, zinc - and possibly other nutrients - are met by the combined availability of nutrients in human milk and endogenous nutrient stores.
In evaluating the nutrient adequacy of exclusive breastfeeding, infant nutrient requirements are assessed in terms of relevant functional outcomes. Nutrient adequacy is most commonly evaluated in terms of growth, but other functional outcomes, e.g. immune response and neurodevelopment, are also considered to the extent that available data permit.
This review is limited to the nutrient needs of infants. It does not evaluate functional outcomes that depend on other bioactive factors in human milk, or behaviours and practices that are inseparable from breastfeeding, nor does it consider consequences for mothers. In determining the optimal duration of exclusive breastfeeding in specific contexts, it is important that functional outcomes, e.g. infant morbidity and mortality, also are taken into consideration.