3.1. New information

In the last few years, there have been many studies of breast milk output with doubly-labelled water and test-weighing procedures that take better account of cultural factors in the family. The main conclusions are:

1. Contrary to existing belief, if allowance is made for the weight of the baby, the milk output of women in developing countries, or of socioeconomically disadvantaged women, is as great as that of more privileged women, i.e., 750-800 mL/d.

2. Except in very high parity women, there is no evidence that milk output is limited by the secretory capacity of the breast.

3. In the populations that have been studied, there is no evidence that altering the energy intake of the mother affects the total energy output in breast milk.

4. One of the most important variables controlling milk output is the infant's weight.

5. It can no longer be assumed that maternal fat stores laid down during pregnancy are available or drawn upon for the support of lactation.