Regulation of Milk Synthesis Secretion and Ejection

Milk volume production is a primary indicator of lactational function; the most precise methods for measuring the volume of milk produced involve weighing infants before and after each feed for 24 h or longer or using an isotope dilution technique with stable isotopes. Clinically, the amount of milk that can be expressed with a breast pump or the change in infant weight after a single feed can be used as a rough index. The volume of milk secreted by women exclusively breast-feeding a single infant at 6 months postpartum is remarkably constant at approximately 800 ml/day in populations throughout the world. Mothers of twins, and occasionally even triplets, are able to produce volumes of milk sufficient for complete nutrition of their multiple infants,

5 Months postpartum

Figure 3 Changes in milk volume during weaning and in response to increased feeding frequency. (A) Milk volume transfer as a function of time postpartum. (B) Relation between feeding frequency (feeds/day) and the milk volume. Data are from five breast-feeding dyads; each symbol represents an individual dyad. (Reproduced with permission from Neville MC et al. (1991) American Journal of Clinical Nutrition 54: 81-92.)

Figure 3 Changes in milk volume during weaning and in response to increased feeding frequency. (A) Milk volume transfer as a function of time postpartum. (B) Relation between feeding frequency (feeds/day) and the milk volume. Data are from five breast-feeding dyads; each symbol represents an individual dyad. (Reproduced with permission from Neville MC et al. (1991) American Journal of Clinical Nutrition 54: 81-92.)

and studies of wet nurses indicate that at least some women are capable of producing up to 3.51 of milk per day. On the other hand, if infants are supplemented with foods other than breast milk, milk secretion is proportionately reduced. This point is illustrated in Figure 3, which shows that milk volumes gradually decline during weaning and increase as feeding frequency increases. These observations illustrate the important principle that the volume of milk secretion in lactating women is regulated by infant demand. If milk cannot be removed from the breast, local mechanisms bring about an inhibition of milk secretion and downregulation of milk synthetic machinery. With partial removal of milk on a consistent basis, these local factors adjust milk secretion to a new steady-state level. If milk removal ceases for extended periods, involution sets in and the gland loses its competency to secrete milk.

New Mothers Guide to Breast Feeding

New Mothers Guide to Breast Feeding

For many years, scientists have been playing out the ingredients that make breast milk the perfect food for babies. They've discovered to day over 200 close compounds to fight infection, help the immune system mature, aid in digestion, and support brain growth - nature made properties that science simply cannot copy. The important long term benefits of breast feeding include reduced risk of asthma, allergies, obesity, and some forms of childhood cancer. The more that scientists continue to learn, the better breast milk looks.

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