In addition, health experts suggest that mothers continue breast-feeding as a primary food source after introducing solid foods and other liquids to their babies. Breast-feeding should continue as an important part of your baby’s diet until he is at least one year old. In Sweden, it is considered unethical to feed infants anything but human milk. To support this belief, a woman is given time off from work for 16 months to nurse her baby, and there are banks of human milk available for those who cannot nurse.
Becky, Emi, and Mari
Mothers produce a unique kind of milk that meets all the nutritional requirements of a newborn baby. Every mammal species is biologically equipped to make milk for babies that support survival in a particular environment for specific developmental needs. For example, mother seals produce milk high in fat because their pups need a plentiful amount of body fat to survive in cold water. For human babies, mental development is key to evolutionary success, so human milk provides nutrients for babies’ rapid brain growth.
In a fascinating example of evolution and physiological intelligence, the composition of breast milk changes to correspond with a growing baby’s needs. The first milk a mother produces is colostrum, which is especially rich in immunity-building cells and antibodies to protect against infections in vulnerable areas such as the nose, throat, ears, lungs, and digestive tract. Colostrum is low in fat, rich in sugars and proteins, and easy for a newborn baby to digest. It is a natural laxative that helps pass your baby’s first stools. Colostrum also helps eliminate bilirubin, which can cause jaundice.
Colostrum is only produced during the first couple of days after giving birth. Milk then changes to transitional milk, which is yellowish in color and contains more lactose, a specific kind of milk sugar that converts easily into energy. Transitional milk is followed by mature milk several days later, which may be bluish in color.
Mature milk undergoes changes during any single nursing session. At the beginning, you produce foremilk, which has a watery, free-flowing consistency that encourages your baby to start nursing. By the end of the session, the breast produces hindmilk, which is a more filling and satisfying milk that is three times richer in fat and higher in protein than foremilk. The proteins, fats, carbohydrates, hormones, vitamins, and minerals in mother’s milk are uniquely proportioned to promote the growth and development of a human infant. As long as your baby is nursing for a full cycle (which is about 15 to 20 minutes), there is no need to wonder if your baby is getting enough nutrients.
Breast milk contains lactose, the carbohydrate that provides energy for a growing baby. It also breaks down into lactic acid, helping to protect him from harmful bacteria.
Milk proteins fall into two categories, curds and whey. The curd portion—the casein protein—appears as white clots, and the liquid is the whey. Human milk has more whey than curd, and the curds are softer and digested more efficiently than the curds in cow’s milk. Comparatively, cow’s milk is mostly casein protein, which forms a rubbery, hard-to-digest curd in a human baby’s stomach. Calves double their birth weight in less than fifty days because they need to grow quickly and walk on their own to forage and eat. To accommodate this growth rate, cow’s milk is significantly higher in protein compared to breast milk. Humans do not need the high concentration of protein in cow’s milk. Breast milk is naturally equipped with healthy protein levels and all of the key amino acids, such as taurine, which plays a critical role in the development of your baby’s brain and eyes.
More than 50 percent of the calories in breast milk come from fat, and much of it contains the cholesterol and saturated fatty acids, or omega-3 fatty acids, necessary for growth and healthy brain development. In addition, breast milk fats contain enzymes that help break down nutrients for absorption. Most fats in breast milk exist in hindmilk, and complete nursing sessions produce more fat-rich hindmilk. Therefore, going through a full cycle in one session when pumping creates whole milk with both foremilk and hindmilk, which includes all the nutrients for healthy development.
Vitamins and Minerals
Although mother’s milk and infant formula may contain the same vitamins and minerals, the micronutrients found in breast milk are more bioavailable than those found in formula. For example, formula has higher levels of calcium, phosphorus, and iron than natural breast milk. However, the bioavailability of these important minerals in breast milk enables your baby to absorb them in just the right dosages. Your baby absorbs 50 to 75 percent of the iron contained in breast milk, while with fortified formula, he absorbs as little as 4 percent of the iron. Manufacturers increase vitamins and minerals to make up for the low bioavailability of these nutrients in formula, making it hard on your baby’s immature intestines and other organs to absorb and dispose of the excess nutrients. Some of that excess—especially iron—can upset the normal balance of his gut and interfere with the growth of healthy bacteria. This can result in constipation and hard, strong-smelling stools.
Breast milk contains hormones that shape brain development and behavior. Researchers have found that the breasts extract hormones from the blood, concentrate them into milk, and generate hormones. A cow’s hormones offer specific nutrients that may align with human babies’ developmental needs in some ways, but cannot provide the necessary hormones that a mother’s milk can. Some of the hormones found in human breast milk are listed below.
- Melatonin helps regulate your baby’s circadian rhythms, including his appetite.
- Oxytocin promotes the experience of a loving bond between mother and child, and helps your baby relax and let go of anxiety.
- Thyroid hormones protect against symptoms of congenital hypothyroidism.
- Bradykinin helps your baby recognize pain.
- Endorphins protect against pain and elevate mood.
- Insulin-like growth factors promotes brain and nervous system development, and healthy skin.