Why should we insist on breastfeeding?

After millions of years of evolution, breast milk has become a perfect multifunctional liquid, and its importance to infant growth is indisputable. Breast milk is called the gold standard of infant nutrition because it can provide all the nutrients and vitamins needed for the development of breastfeeding infants. Breastfeeding can effectively reduce infant mortality and the incidence of infectious diseases.

Dr. Thierry Hennet and Dr. Lubor Borsig of the University of Zurich in Switzerland summarized the six major functions of breast milk, pointing out that breastfeeding can protect infants and mothers. The multiple bioactive factors provided by breast milk work together to strengthen the infant's mucosal immune system, cultivate intestinal flora, promote the infant's physical development, and regulate the mother's hormone levels and birth interval.

Breastfeeding protects babies and mothers

Recent studies have highlighted the benefits of breastfeeding - reducing infant mortality and morbidity in the short term, reducing the risk of obesity in the long term , and even helping mothers protect against breast and ovarian cancer . Given the impact of breastfeeding on children's health, the World Health Organization (WHO) recommends exclusive breastfeeding for the first six months of an infant's life, and supplementing solid foods with breast milk for at least a year thereafter.

Provides nutrients and energy as food

Breast milk is an excellent nutrient for rapidly growing newborns. In particular, colostrum—the milk secreted by the mother before or immediately after birth—contains high concentrations of protein and beneficial carbohydrates. In human breast milk, race and maternal age have little effect on the overall composition of breast milk, but the maximum amount of nutrients varies at different stages of lactation. Generally speaking, colostrum has the highest content of active proteins and oligosaccharides, while mature breast milk has a correspondingly higher content of lipids and casein. Lipids provide 40%-50% of the dietary energy in breast milk and are the largest source of calories.

Fertilizer for beneficial bacteria in infants' guts Human breast milk contains more than 200 different sugar molecules, far more than the average of 30-50 found in mouse or cow milk, making it the most complex of all mammals. Breast milk helps support the growth of healthy bacteria in infants' guts.

At birth, babies only have the flora they get from their mothers. To protect themselves, babies need more flora to build a healthy microbiome. The large amount of sugars in breast milk are essential nutrients for the survival and growth of these flora. "Babies don't have the mechanism to digest these sugars, so they are first used by the flora," said Thierry Hennet. "It's like a sowing field, and breast milk is the fertilizer."

Protective umbrella for baby's immune system

Breast milk contains biologically active proteins such as physiological immunoglobulins, cytokines, defensins and lactoferrin that help infants with immune protection. These active proteins can remain active when transported to the stomach and intestines because the pH value in the infant's intestine is about 3-5, which is higher than the 1-2 of adults. The protein stability of breast milk is maintained to avoid intestinal hydrolysis. In addition, breast milk also provides passive immune protection factors to help the infant's inherent immune system fight infection.

Coordinating the body's biological clock

Like the body's biological clock, breast milk helps regulate the mother's hormone cycle and helps the baby wean. During pregnancy, progesterone inhibits the pituitary gland from secreting prolactin, preventing the mother from lactating too early. Once the baby is born, progesterone levels drop and prolactin increases, and the mother begins to secrete milk. During lactation, due to the increase in prolactin and low gonadotropin levels during lactation, the maturation of ovarian follicles is inhibited, thus preventing lactating women from becoming pregnant immediately.

In order for lactose to be absorbed by the intestine, it must first be processed by lactase. However, the expression of lactase is strictly regulated and is gradually shut down in most children between the ages of 2 and 3. Reduced lactase activity causes lactose to enter the large intestine, where metabolized microorganisms release hydrogen, methane, carbon dioxide, and lactic acid. These fermentation products cause bloating, abdominal cramps, and nausea, which are typical symptoms of lactose intolerance. The appearance of this symptom will cause breastfeeding infants to refuse breast milk until they are naturally weaned.

Regulate the baby's physical development

In addition to contributing to the development of intestinal flora and the maturation of the mucosal immune system, breast milk can also affect metabolic pathways and promote the growth and development of infants. Several hormones in breast milk have regulatory functions like endocrine factors. For example, leptin in breast milk controls satiety and fat storage; insulin-like growth factor 1 (IGF1) stimulates body growth; and adiponectin regulates blood sugar levels and fatty acid oxidation. These hormones play a role in the early growth of breastfed infants.

Attention: Transporting harmful substances accumulated in the mother's body

However, although breast milk can provide protective substances, it may also transport lipophilic harmful chemicals such as pesticides, heavy metals, synthetic additives and endocrine disruptors accumulated in the mother's breast tissue to the baby. In addition, breast milk can also transmit pathogens such as human immunodeficiency virus (HIV) and cytomegalovirus (CMV) to the baby. The Centers for Disease Control (CDC) recommends that HIV-positive mothers should avoid breastfeeding.

In short, breastfeeding has many benefits. Unless the mother has some contraindications such as mother-to-child transmitted diseases, breastfeeding is generally possible. Infant formula that meets the nutritional needs of infants is also a safe choice. Researchers will continue to explore the role of different molecules in breast milk, and as sequencing technology develops, such research results will become more and more abundant. In the next few years, it is possible to have a new understanding of the hormones in human breast milk and a new understanding of the specific role of bacterial populations in the infant's intestine.

References:

Hennet T, Borsig L. Breastfed at Tiffany's. Trends Biochem Sci. 2016 Jun;41(6): 508-18.

Cell Press. Unique biology of human breast milk . AAAS EurekAlert.19 April 2016.