Human Milk - A Biological System

Introduction

Breastfeeding is a natural process that offers benefits for both mother and child. Breast milk consists of many essential nutrients and antibodies required for infants' healthy growth. There are many short-term and long-term benefits for infants if they are fed with breast milk. Mothers who breastfeed have a lower risk of developing many diseases, including ovarian cancer, type 2 diabetes, and hypertension. Recent studies and evidence suggest that human milk can be considered a biological system as it offers nutrition and protection to the baby and has a key role in enhancing the bond between mother and child. In addition, many factors can impact the composition of human milk.

What Is a Biological System?

Before knowing whether human milk is a biological system, it is important to understand the meaning of the biological system. It is defined as a unit or group of organs or entities that work simultaneously to carry out a specific function or task. Many biological systems work together in the human body to carry out specific functions. The biological systems in humans include nervous, muscular, reproductive, cardiovascular, lymphatic, skeletal, immune, respiratory, and endocrine systems. The respiratory system, nose, mouth, pharynx, larynx, trachea, lungs, and diaphragm work together to carry out the process of respiration. Similarly, in other systems, their parts or units work together to carry out particular functions.

How Does the Composition of Breast Milk Act as a Biological System?

The specific components in human milk play a major role in ensuring the healthy growth and development of infants. Human milk contains macro and micronutrients as well as non-nutritive substances. These components have been studied in past years to understand their importance in infants’ development. Following are the nutrient components of human milk and their assumed functions:

• Water: Breastfed infants meet their water requirements through milk.

• Carbohydrates: Lactose and human milk oligosaccharides (HMOs) are the most abundant carbohydrates in human milk. The functions of HMOs include controlling intestinal microbes, anti-adhesive or repulsive effects against disease-causing microbes, and developing the immune system.

• Proteins: More than 400 proteins are present in human milk with a variety of health benefits.

• Lipids: Lipids in human milk act as the storehouse of half of the energy of human milk.

• Micronutrients: Human milk is an important source of micronutrients for infants. Vitamins and minerals are required for the proper growth and development of infants.

In addition to nutrient constituents, human milk consists of bioactive components with many health benefits for infants. Some of them are:

• Immunoglobulins: Immunoglobulin A or IgA is the most abundant immunoglobulin in human milk. It protects the infant with its antimicrobial, anti-inflammatory, and immunomodulatory mechanisms.

• Hormones: The important hormones present in human milk are leptin and ghrelin, which helps in weight gain and proper growth of infants.

• Proteins: The bioactive proteins in human milk are lactoferrin and osteopontin. Lactoferrin helps in cell growth and iron absorption and has the property to stop bacterial growth. Whereas osteopontin is a protein that has a major role in developing bone and cartilage.

• White Blood Cells (WBCs): Providing immunity to infants or protecting them from infections is the main function of WBCs in human milk.

• Cytokines: Their functions include anti-inflammatory, enhancing immunity, and promoting growth in infants.

Due to the presence of many nutritive and non-nutritive or bioactive components, human milk can be considered a complex biological system. These components, along with the microbes in human milk, assist in the transition to life outside the womb.

What Are the Factors That Affect the Composition of Human Milk?

Various maternal and infant factors can have an impact on the composition of human milk.

• Maternal Factors: After the establishment of lactation, infant demand is the main factor for the synthesis of milk and its production. Non-modifiable factors like the genetics of the mother and modifiable factors such as diet and environment influence the composition of milk. The amount of vitamins such as thiamine, riboflavin, vitamin B6, vitamin B12, and choline in breast milk can be influenced by the diet and nutritional status of the mothers. Certain environmental and lifestyle factors such as smoking, alcoholism, exposure to toxins and chemicals, vegetarianism, and use of contraceptives can also affect the composition of breast milk. Malnutrition in mothers can impact the volume and nutrient levels of breast milk. Postpartum infection, overweight, and obesity in mothers after delivery can cause early cessation or stoppage of breastfeeding. The knowledge of the effect of geography and ethnicity on the composition of breast milk is limited.

• Infant Factors: There exists a two-way communication between the microbiota present in the oral cavity of infants and the breast milk, which can assist in direct signaling from the infant to the mother. When the infant sucks milk from the nipples, pressure is created within the ducts in the mammary glands. These intraductal pressures can have an impact on the composition of the breast milk.

Why Is Breastfeeding Recommended for the First Six Months of Life?

There are numerous reasons why breastfeeding is highly recommended for the first six months of life:

• It can meet all the nutritional requirements of newborns, provides immunity, promotes growth and development, and improves the maturity of the gut.

• Breastfeeding after six months of age can also improve the immunity and nutritional status of the infants.

• The milk secreted 4 to 5 days after birth is known as colostrum. It is yellowish and is rich in carotenoids, calcium, sodium, immunoglobulins, and other proteins. It is highly advised to feed newborns with colostrum due to its benefits.

• Breastfeeding lowers the risk of many diseases including obesity, diabetes, sudden infant death syndrome (SIDS), and asthma in infants.

Conclusion

Breast milk is a biofluid produced by the mothers after delivery. It has many constituents that play a major role in the growth and development of infants. Various factors can affect the composition of human breast milk, and breast milk itself is considered a biological system like any other system in the body. The hormones, mammary glands, mammary ducts, breasts, nipples, and infants’ oral cavities are included in this biological system. Breast milk, as a biological system, provides health benefits to both mother and child as well as aids in enhancing the bond between them.