A close new look at the substances contained in human breast milk is yielding a surprise: Mother’s milk may protect against cancer, a Swedish research team said Monday.
The discovery, reported in the Proceedings of the National Academy of Sciences, finds that alpha-lactalbumin, an abundant natural protein in mother’s milk, somehow stimulates cancer cells to commit suicide in their laboratory dish experiments, the scientists said.
They also found that the same substance leaves normal, mature cells alone, unharmed. This suggests that alpha-lactalbumin targets only cells that are growing abnormally, capable of forming tumors. The cells are killed by a process called apoptosis, or programmed cell death.
The Swedish researchers said their discovery “could lead to the design of anti-tumor agents” that might be useful against cancer in adults. Such work would take advantage of a natural system that directs the infant’s intestinal tract toward maturity and away from cancer.
“While investigating the effect of human milk” on the ability of bacteria to stick to lung cancer cells, they said, “we were surprised to discover that the milk killed the cells.” The researchers are Anders Hakansson, Boris Zhivotovsky, Sten Orrenius, Hemant Sabharwal and Catherine Svanborg, at the Karolinska Institute in Stockholm.
For the experiments, they used milk from several different donors in their experiments, with similar results. They also found that the protein, alpha-lactalbumin, must be in the form of several molecules clumped together. Singly, the molecules are inactive.
According to cell biologist Keith Mostov at the University of California, San Francisco, the findings are too new to be interpreted. “It remains to be seen what its significance or biological relevance really is. But it certainly is a surprise; not like anything I’ve heard of before.”
To find out what substance in the milk kills the cells, the Swedish team used laboratory techniques to separate the milk’s various components. The cell-killing capability was found in the component called casein. Then, further analysis showed that alpha-lactalbumin is the active agent.
It has long been known that breast milk is of great value to the health of infants. In addition to nutrients, breast milk contains molecules that suppress bacteria, viruses and protozoans. “As a result, breast-feeding protects the infant from respiratory and gastro-intestinal infections,” the researchers said.