The longstanding debate over the optimal duration of exclusive breastfeeding has centered on the so-called “weanling’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 requirements beyond 4 months of age. The debate over whether to recommend exclusive breastfeeding for 4–6 months vs “about 6 months” has recently become more intense.

The optimal duration of exclusive breastfeeding. A systematic review, 2002.

The optimal duration of exclusive breastfeeding. Report of the expert consultation on the optimal duration of exclusive breastfeeding.
Geneva, Switzerland 28–30 march 2001, 2002

Nutrient adequacy of exclusive breastfeeding for the term infant during the first six months of life, 2002