Breast milk

Two 25ml samples of human breast milk. The left hand sample is Foremilk, the watery milk coming from a full breast. The right hand sample is Hindmilk, the creamy milk coming from a nearly empty breast.

Breast milk refers to the milk produced by a mother to feed her baby. It provides the primary source of nutrition for newborns before they are able to eat and digest other foods; older infants and toddlers may continue to be breastfed. The baby nursing from its own mother is the most ordinary way of obtaining breastmilk, but the milk can be pumped and then fed by baby bottle, cup and/or spoon, supplementation drip system, and nasogastric tube. Breastmilk can be supplied by a woman other than the baby's mother; this is known as wetnursing.

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 syndrome may require hormone replacement.

Lack of supply can be addressed by nursing and/or pumping more frequently. The more the mother nurses her baby, or pumps, the more milk is produced. 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. Increasers of milk supply are known as galactagogues.

Composition

The exact integrated properties of breast milk are not entirely understood, but the nutrient content after this period 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.

Mother's milk has been shown to supply a type of endocannabinoid (the natural neurotransmitters which marijuana simulates), 2-Arachidonoyl glycerol.

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 infant formula was considered superior to breast milk.

However, it is now universally recognized that there is no commercial formula that can equal breast milk. In addition to the appropriate amounts of carbohydrate, protein and fat, breast milk also provides vitamins, minerals, digestive enzymes and hormones - all of the things that a growing infant will require. Breast milk also contains antibodies and lymphocytes from the mother that help the baby resist infections. The immune function of breastmilk is individualized, as the mother, through her touching and taking care of the baby, comes into contact with pathogens that colonize the baby and consequently her body makes the appropriate antibodies and immune cells. This is a process that obviously cannot be replicated on an industrial basis.

Women who are breastfeeding should consult with their physician regarding substances that can be unwittingly passed to the infant via breast milk, such as alcohol, viruses (HIV or HTLV-1) or medications.

Most women who do not breastfeed use infant formula, but breast milk donated by volunteers to human milk banks can be obtained by prescription. Cow's milk is recommended as a substitute, but only for children over one year of age.

Comparison to other milks

All mammal species produce milk, but the composition of milk for each species varies widely and other kinds of milk are often very different from human breast milk. As a rule, the milk of mammals that nurse frequently (including human babies) is less rich, or more watery, than the milk of mammals whose young nurse less often. Human milk is noticeably thinner and sweeter than cow's milk. Left in a cup, the cream will rise and form a thin layer.

Whole cow's milk does not contain sufficient vitamin E, iron, or essential fatty acids, which can make infants fed on cow's milk anemic. Whole cow's milk also contains excessive amounts of protein, sodium, and potassium which may put a strain on an infant's immature kidneys. In addition, the proteins and fats in whole cow's milk are more difficult for an infant to digest and absorb than the ones in breast milk. Evaporated milk may be easier to digest due to the processing of the protein but is still nutritionally inadequate. A significant minority of infants are allergic to one or more of the constituents of cow's milk, most often the high amounts of lactose (milk sugars) and agglutinin. These problems can also affect infant formulas derived from cow's milk.

Extraordinary consumption

In the ancient world, breast milk was sometimes consumed by fertility cults, and in other religious ceremonies.

Preliminary research indicates that breast milk can induce apoptosis in some types of cancer cells . Adults with GI disorders and organ donation recipients can also benefit from the immunologic powers of human breast milk. More research is needed in these areas.

In Costa Rica, there have been trials to produce cheese and custard from human milk as an alternative to weaning.

A controversial Swiss restaurateur has created a menu based around foods cooked in human breast milk .

See also

• Lactation
• Male lactation
• Breast pump
• Human milk banking in North America
• Infant formula

External links

• Comparison of Human Milk and Formula
• La Leche League Human Milk Storage Information
• Children's Health Topics: Breastfeeding
• Infant nutrition information from Seattle's Children's Hospital and Regional Medical Center
• Moms pay big for other mothers' milk, Janine DeFao, San Francisco Chronicle, 9 April 2006. An article about the market on human milk.