Breast milk
Breast milk usually refers to the milk produced by a human female. Under the influence of the hormones prolactin and oxytocin, women produce milk after pregnancy to feed their baby. The initial milk produced is often referred to as colostrum, which is high in the immunoglobulin IgA, which coats the gastrointestinal tract. This helps to protect the newborn until its own immune system is functioning properly along with creating a mild laxative effect, expelling meconium and helping to prevent the build up of bilirubin (a contributory factor in jaundice).
The exact composition of breast milk varies from day to day, depending on food consumption and environment, meaning that the ratio of water to fat fluctuates. Foremilk, the milk released at the beginning of a feed, is watery, low in fat and high in carbohydrates relative to the creamier hindmilk which is released as the feed progresses. The breast can never be truly "emptied" since milk production is a continuous biologic process.
Though now it is almost universally prescribed, in the 1950s the practice of breastfeeding went through a period where it was out of vogue and the use of artificial formula was considered superior to breast milk.
