Production

Under the influence of the hormones prolactin and oxytocin, women produce milk after childbirth to feed the 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, and creates a mild laxative effect, expelling meconium and helping to prevent the build up of bilirubin (a contributory factor in jaundice).

There are many reasons a mother may not produce enough breast milk. Some of the most common are an improper latch (i.e. the baby does not connect efficiently with the nipple), not nursing or pumping enough to meet supply, certain medications (including the contraceptive pill), illness, and dehydration. A rarer reason is Sheehan's syndrome, also known as postpartum hypopituitarism, which is associated with prolactin deficiency; this rare syndrome may require hormone replacement.

Lack of supply can be addressed by nursing and/or pumping more frequently.Fact: date=March 2008 The more the mother nurses her baby, or pumps, the more milk is produced.Fact: date=March 2008 It is very helpful to nurse on demand - to nurse when the baby wants to nurse rather than on a schedule. If pumping; it is helpful to have an electric high grade pump so that all of the milk ducts are stimulated. Some mothers try to increase their milk supply in other ways - by taking the herb fenugreek, used for hundreds of years to increase supply ("Mother's Milk" teas contain fenugreek as well as other supply-increasing herbs); there are also prescription medications that can be used, such as Domperidone (off-label use) and Reglan.Fact: date=March 2008 Increasers of milk supply are known as galactagogues.

Composition

The exact integrated properties of breast milk are not entirely understoodFact: date=March 2008, but the nutrient content after this periodFact: date=March 2008 is relatively consistent and draws its ingredients from the mother's food supply. If that supply is found lacking, content is obtained from the mother's bodily stores. 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 biological process.

Human milk contains 0.8% to 0.9% protein, 3% to 5% fat, 6.9% to 7.2% carbohydrates and 0.2% ash (minerals). Carbohydrates are mainly lactose; several lactose-based oligosaccharides have been identified as minor components. The principal proteins are casein homologous to bovine beta-casein, alpha-lactalbumin, lactoferrin, IgA, lysozyme and serum albumin. Non-protein nitrogen-containing compounds, making up 25% of the milk's nitrogen, include urea, uric acid, creatine, creatinine, amino acids and nucleotides.