Milk is not just food. The more closely scientists examine it, the more complexity they find.
Along with nutrients like protein and calcium, milk contains immune factors that protect infants from disease. It hosts a menagerie of microbes, too, some of which may colonize the guts of babies and help them digest food. Milk even contains a special sugar that can fertilize that microbial garden.
Now, it turns out, milk also contains messages.
A new study of monkeys, published in the journal Behavioral Ecology, demonstrates that a hormone present in milk, cortisol, can have profound effects on how babies develop. Infant monkeys rely on cortisol to detect the condition of their mothers, the authors suggest, then adjust their growth and even shift their temperaments.
Jeffrey French, a neuroendocrinologist at the University of Nebraska at Omaha who was not involved in the study, praised its “remarkable sophistication” and said that it helped to change how we think about breast milk. “Milk serves almost like a pheromone, a chemical signal sent from one individual to another,” he said.
Cortisol serves many functions in mammals, but it is best known as a stress hormone. When cortisol courses through our bodies, it prepares us to handle alarming or fearful situations, increasing the brain’s consumption of glucose and suppressing the digestive system.
The cortisol in a mother’s body can also end up in her milk. Babies appear to be remarkably sensitive to the hormone as they nurse. Scientists have found that drinking milk causes infants to rapidly build receptors in their intestines for detecting cortisol. The same shift doesn’t happen when babies drink formula.
Read full original article: In a Mother’s Milk, Nutrients, and a Message, Too
