Not all the properties of [[breast milk]] are understood, but its [[nutrient]] content is relatively stable. Breast milk is made from nutrients in the mother's bloodstream and bodily stores. Because breastfeeding uses an average of 500 calories a day it helps the mother lose weight after giving birth.<ref>Dewey KG, Heinig MJ, Nommwen LA. Maternal weight-loss patterns during the menstrual cycle. Am J Clin Nutr 1993;58: 162-166</ref> The composition of breast milk changes depending on how long the baby nurses at each session, as well as on the age of the child.
Research shows that the milk and energy content of breastmilk actually decreases after the first year.<ref name="WHO_breastfeeding" /> Breastmilk adapts to a toddler's developing system, providing exactly the right amount of nutrition at exactly the right time.<ref name="Gartner_2005" /> In fact, research shows that between the ages of 12 and 24 months, 448 milliliters of human milk provide these percentages of the following minimum daily requirements:<ref>[http://www.mothering.com/articles/new_baby/breastfeeding/extended-breastfeeding.html]</ref>
