Nutrition Science and Everyday Application - beta v 0.1

NUTRITION IN EARLY INFANCY 591
Nutrient Composition of Breast Milk
The first milk, called colostrum, is produced immediately after birth and continues for the
first two to five days after the arrival of the baby. Colostrum is yellowish in color, thicker than
mature breast milk, and produced in small quantities. It is low in fat and easily digestible, yet
rich in protein, fat-soluble vitamins, and minerals. Colostrum is also a concentrated source of
immunoglobulins that pass from the mother to the baby and provide immune protection to
the newborn. The stomach capacity of newborns is small, so they only consume a teaspoon
or two of colostrum per feeding in the first few days of life, but they need to feed often.
Frequent, on-demand feeding (whenever the baby is hungry, not on a schedule) helps to
promote full milk production. 5
After a couple of days, colostrum is replaced by transitional milk, which is produced in
much greater volume and lasts through 7 to 14 days postpartum. Compared with colostrum,
transitional milk has more fat and lactose, and less protein and immunoglobulins, and it is
also more calorie-dense. Finally, women begin to produce mature milk and will continue to
make this type of milk through the end of lactation. Mature milk contains about 87% water,
4% fat, 1% protein, and 7% lactose. Together, these meet infants’ macronutrient and caloric
requirements. 9
However, there is variability even within mature milk. In a given feeding, the milk secreted
at the beginning of the feeding (called foremilk) is thinner and higher in lactose than the milk
at the end of the feeding (called hindmilk). The higher levels of fat in the hindmilk helps to