The human body, when looked at in enough detail, is truly miraculous. A study in 2009 found that human breast milk actually varies its composition throughout the day, sending circadian signals to the infant to help regulate its biology appropriately. Among many different nutritional factors, the milk varied in composition by providing more cortisol in the daytime and more melatonin at night. Another study has found that, when the baby is ill, the mother's breast milk provides more immune...