Infant Feeding

The newborn’s diet must supply calories and nutrients, including carbohydrates, proteins, fats, vitamins, and minerals needed to support the rapid growth and development that occurs in early life. During the first few months of life, nutritional needs can be met by either breast milk or commercially prepared cow's milk–based formula.

Alright, let's look at the composition of breast milk, which differs with each of the three phases of milk production, also known as lactogenesis.

Phase I of lactogenesis starts during pregnancy and continues through the first few days of postpartum. During this phase, the breasts produce an early version of breast milk called colostrum which is a thick, yellowish fluid, high in protein, vitamins, minerals, and immunoglobulins like IgA, which protect the infant’s gastrointestinal tract from infections and aids in establishing normal flora in the infant’s digestive tract. Colostrum is low in fat and carbohydrates. It also has a laxative effect, which promotes the passage of the infant’s first bowel movement called meconium.

Next, Phase II of lactogenesis starts two to three days postpartum. The milk produced during this phase is called transitional milk. Compared to colostrum it contains less immunoglobulins and proteins, but has more vitamins, fats, and lactose.

The last phase of lactogenesis is Phase III, when mature milk is produced. Mature milk is the ideal food for infants, though it’s low in vitamin D, so a daily supplement of 400 international units, or IUs, is recommended until the baby starts eating solid foods. Mature milk is also low in iron, but since the iron found in breast milk is easily absorbed, supplementation is not needed.

Now, the nutritional content of mature breast milk will vary during the course of the feeding session. So, foremilk, which is the first milk that flows from the breast, is rich in protein and carbohydrates, and low in fat and calories. It is also quite watery, so it quenches the infant’s thirst. On the flip side is hindmilk, which is the milk near the end of feeding, is rich in fat and higher in calories.

Alright, now let’s switch gears and discuss infant formulas. Standard infant formulas are based on cow’s milk that’s been modified by decreasing the protein content, replacing the butterfat with vegetable oil, and adding carbohydrates and essential nutrients such as vitamins and minerals, especially iron.

There are also other formulas for infants with special needs. For example, there are hydrolyzed formulas, where the protein has been broken down into smaller sized proteins than those found in standard cow's milk-based formula. This type of formula is used when milk protein allergy is suspected, because the hydrolyzed proteins are less likely to stimulate antibody production.