by Katherine Brind Amour
December 07, 2009

A series of research studies conducted by Dr. Mark Cregan suggest that breast milk may hold the key not only to the healthy development of infants, but to overcoming some of the ethical qualms of stem cell research as well.

Cregan’s discovery of mammary epithelial and immune system stem cells in breast milk demonstrates that adult stem cells are present in expressed human milk. It is unclear whether these cells behave like other adult stem cells, which would mean these cells could be a source for tissue growth and infection-fighting therapies for a variety of health conditions.

Cregan hopes that the presence of stem cells in human milk may further explain some of the many benefits of breastfeeding over formula-feeding. He believes that stem cells may even serve as a guide for muscle, bone, and immune system development after birth.

There has been little research on these exact topics since Cregan’s exploratory study in 2007, and until scientists determine whether the cells in breast milk behave like adult stem cells progress is likely to be slow. If scientists find that the stem cells in human milk behave like adult stem cells, it may be possible to “reprogram” them or force them into becoming specific types of tissues and cells.

Like any stem cell technology, research on breast milk stem cells will be time-consuming and expensive. Another challenge to the rapid advancement of breast milk stem cell research is its relative obscurity; research on other sources of stem cells is more widely practiced and better developed, and thus more frequently funded.

Although the study of breast milk stem cells is in its infancy, the readily available supply of breast milk and the non-invasive technique for collecting it would weigh highly in its favor as a source for stem cells for research if the cells prove to behave like adult stem cells.

Stem cell basics
Stem cells are cells that have the ability to develop into different types of cells. When a stem cell divides, each new cell has the potential either to remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a brain cell.

Multiple therapies using adult stem cell technologies already exist, and many more are in clinical trials. Adult stem cells are different from embryonic stem cells; adult stem cells theoretically have the capacity to turn into any tissue or organ of their original general cell type, while embryonic stem cells theoretically have the capacity to turn into any cell type or tissue in the body, and can even generate an entire new body.

Retrieving embryonic stem cells for research, however, is often considerably more controversial than collecting adult stem cells. Harvesting embryonic stem cells means destroying embryos. Adult stem cells can come from many different sources, such as umbilical cord blood, the heart, and bone marrow.

Because stem cells can generate tissue, and even entire organs, they can be used to repair or replace damaged cells or tissues in the body. The regenerative and healing properties of stem cells demonstrate their effectiveness by performing routine repairs in the body and offer significant potential for treating disorders and illnesses.

Breast milk stem cells
Although there is no evidence to support the idea that maternal stem cells transferred to the baby in breast milk affect the baby’s health, the concept is scientifically plausible. It’s already been demonstrated that some stem cells survive digestion in the baby’s gut and could theoretically be absorbed into the baby’s system. Adult stem cells that are already programmed may, according to Dr. Cregan, help guide a child’s development by promoting healthy growth and improving a baby’s defense systems.

The significance of this research is of the identification of additional components of human milk that are distinct from formula. The exact impact of these stem cells on the baby may eventually be clarified, but until then, breastfeeding women can take pride in the fact that their milk may be biologically designed to promote their child’s healthy transition into adulthood.