Composition of Breast Milk
By Laura Silvas, RN IBCLC
We are all aware that breast milk is packed full of magical nutritional benefits that perfectly support your child’s development, but did you know that the composition of breast milk changes over time? Read on to learn more about breast milk's properties and how it transforms to meet your baby’s changing needs.
In addition to carbohydrates, proteins, fats, and water, breast milk is composed mainly of water, lipids, and a spectrum of live bioactive agents – elements that affect different functions in the body. Breast milk also contains stem cells and a range of hormones that play an important role in your baby’s development.
Breast milk is composed of both foremilk and hindmilk, which vary in composition. See below for more details:
Human breast milk is composed of about 87% water. It essentially provides all the hydration your baby needs to survive. It helps regulate their body temperature and protects their organs.
Lipids (or fats) only comprise about 4% of breast milk but provide around half the calories your baby receives from breast milk. The fat content of breast milk varies from woman to woman and is higher in the evening. Fats are a good source of energy, cholesterol, and essential fatty acids necessary for developing your baby's brain, nervous system, and vision.
Carbohydrates are the main energy source found in breast milk. They are mainly composed of sugars known as lactose. Interestingly, human milk contains more lactose than cow’s milk and is the preferred energy source for the brain.
Proteins are essential to breast milk and help build, strengthen, and repair the body's tissue. They are also required to make hormones, enzymes, and antibodies, which help the body function and ward off diseases. There are two different types of proteins in breast milk – whey and casein. The whey-to-casein ratio in human milk fluctuates between 80:20 and 70:30 during early lactation and decreases to 50:50 in late lactation. This is significantly greater than the proportion found in cow’s milk, where the whey component makes up only 18% of the milk. This explains why it is so difficult for infants to digest cow’s milk.
Whey protein, when digested, remains liquid, which is easier for the infant’s body to process. They also contain antibodies, which, as mentioned earlier, help your baby to fight infections.
Casein is a larger, more complex protein that often forms clots or curds in the stomach.
There are 20 amino acids present in breast milk. Amino acids are the building blocks of proteins. Research shows that amino acids play an important role in immune development. They support the growth of nervous system tissues and brain and eye development.
Bioactive components are abundant in breast milk and passed from the mother to her baby. These bioactive components include antibodies (or immunoglobulins) which help fight illnesses and disease, building up the baby’s immunity. They aid in preventing common colds, ear infections, diarrhea, vomiting, and other potential infections. Stem cells are also bioactive agents found exclusively in breast milk, which help with the development and healing of organs.
Hormones are also passed from the mother’s breast milk to her baby. They are essential in promoting growth and development, helping regulate the baby’s metabolism, blood pressure, and pain responses, and influencing baby’s growth.
Enzymes are found in abundance in breast milk. They perform many important functions, including providing immune support, aiding digestion to break down the fats and proteins so that they can be absorbed by the baby’s body, and helping with infant development.
Micronutrients, including vitamins and minerals, are also found in breast milk. Vitamins support the development of healthy bones, skin, and muscles and prevent malnutrition-related issues such as scurvy and rickets. Minerals are required to ensure that your baby’s body grows healthy and strong. They help develop strong bones and red blood cells and ensure proper nerve and muscle function.
Conclusion
Breast milk is an excellent source of nutrition for growing infants. It provides all the essential nutritional properties your baby needs for optimal growth and development. If you are having trouble breastfeeding, talk to your doctor or lactation consultant.