Overview of the Enzymes in Breast Milk

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An enzyme is a substance (usually a protein) that creates a chemical reaction in the cells of the body. Enzymes perform important functions that are necessary for survival, including those involved in digestion and metabolism. Each enzyme has only one job, and it's specific to the type of chemical reaction that it produces. 

The Enzymes Found in Breast Milk

There are many different enzymes found in human breast milk. These enzymes play an important role in the health and development of a newborn child. The enzymes in breast milk serve a variety of functions, some of which are still poorly understood by medical experts.

Some enzymes are necessary for the function of the breasts and the production of breast milk, some enzymes help a baby with digestion, and others are essential for a child's development. Here are the most important enzymes found in breast milk.


Amylase is the main carbohydrate-digesting enzyme in the human body. Since babies are born with an immature pancreas (the organ that produces most of the body's amylase), they get most of this essential digestive enzyme through breast milk.

Soon after birth, a child's pancreas begins to mature and by 2 years of age the pancreas is functioning at adult capacity.


Lipase, the fat-digesting enzyme, is required for newborns to fully digest and use the fat in breast milk. Lipase breaks down milk fat and separates it into free fatty acids and glycerol (a type of carbohydrate).

Similar to amylase, most of the body's lipase is produced in the pancreas. The lipase in breast milk makes free fatty acids available to newborns until their pancreas is mature enough to begin producing this enzyme.

Lipase is also responsible for the soapy, metallic smell that refrigerated or previously frozen and thawed breastmilk sometimes has. The freezing and thawing of breast milk high in lipase can cause the fat in the milk to break down quickly, leaving an unpleasant odor. It may not smell good, but the nutritional value is still present.


Protease speeds up the breakdown of proteins. There are high levels of protease in breast milk. It is believed that this enzyme is important for digestion, especially during the period right after birth.


Lactoferrin is a protein with enzymatic activity that helps a baby absorb iron. Along with white blood cells and antibodies, lactoferrin also kills bacteria. This enzyme prevents E. coli from attaching to cells and helps to prevent infant diarrhea.

Lactoferrin also prevents the growth of Candida albicans, a fungus. Lactoferrin levels are very high in preterm breast milk and the levels go down as lactation continues.


Lysozyme acts as a natural antibiotic, protecting breastfed infants from bacteria such as E. coli and Salmonella. The levels of lysozyme in the breastmilk rise as milk transitions from colostrum to mature milk. This increase helps to protect children from germs that can cause illness and diarrhea.

Other Enzymes in Breast Milk

Some of the other active enzymes in breast milk include diastase, lactose synthetase, and lactoperoxidase. Research is still uncovering new proteins with enzymatic activity, so we are not sure yet how many enzymes are present in breast milk.

Are There Enzymes in Infant Formula?

Infant formulas do contain enzymes, but many of the enzymes found in breast milk are not in formula. Formula manufacturers add some enzymes, and some are found naturally. However, enzymes found in milk are specific to the species that make that milk.

For example, human breast milk contains enzymes made for human babies, and cow's milk contains enzymes made for a cow's calf. Therefore, infant formula that is cow's milk-based does not have the same levels of human enzymes as human breast milk. Even when companies add enzymes to infant formula, it cannot match what's in breast milk.

7 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Human Genome Research Institute. Enzyme.

  2. Martin CR, Ling P-R, Blackburn GL. Review of infant feeding: key features of breast milk and infant formula. Nutrients. 2016;8(5). doi:10.3390/nu8050279

  3. National Pancreas Foundation. Childhood inherited pancreatic disorders.

  4. Mount Sinai. Lipase.

  5. Khaldi N, Vijayakumar V, Dallas DC, et al. Predicting the important enzymes in human breast milk digestion. J Agric Food Chem. 2014;62(29):7225-7232. doi:10.1021/jf405601e

  6. Breastfeeding. 7th ed. W.B. Saunders; 2011.

  7. Ella E, Ahmad A, Umoh V, et al. Studies on the interaction between IgA, lactoferrin and lysozyme in the breastmilk of lactating women with sick and healthy babies. Journal of Infectious Diseases and Immunity. 2011; 3(2): 24-29.

Additional Reading
  • Lawrence, Ruth A., MD, Lawrence, Robert M., MD. Breastfeeding A Guide For The Medical Profession Seventh Edition.  Mosby. 2011.
  • Riordan, J., and Wambach, K. Breastfeeding and Human Lactation Fourth Edition. Jones and Bartlett Learning. 2014.

By Melissa Kotlen
Melissa Kotlen is an International Board-Certified Lactation Consultant and Registered Lactation Consultant.