Breast milk, to be specific human milk, is the milk produced by the breasts (or mammary glands) of a human female for her infant offspring. Milk is 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, either exclusively or in combination with other foods.
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; either via donated pumped milk (for example from a milk bank), or when a woman nurses a child other than her own at her breast — an ancient and storied practice known as wetnursing.
The World Health Organization recommends exclusive breastfeeding for the first six months of life, with solids gradually being introduced around this age when signs of readiness are shown. Supplemented breastfeeding is recommended until at least age two and then for as long as the mother and child wish.[2]
Breastfeeding continues to offer health benefits into and after toddlerhood.[3] These benefits include lowered risk of Sudden Infant Death Syndrome (SIDS),[4] increased intelligence, decreased likelihood of contracting middle ear infections, cold, and flu bugs, a tiny decrease in the risk of childhood leukemia, lower risk of childhood onset diabetes, decreased risk of asthma and eczema, decreased dental problems, decreased risk of obesity later in life, and decreased risk of developing psychological disorders.[5][6]
Breastfeeding also provides health benefits for the mother. It assists the uterus in returning to its pre-pregnancy size and reduces post-partum bleeding, as well as assisting the mother in returning to her pre-pregnancy weight. Breastfeeding also reduces the risk of breast cancer later in life.[7]
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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).
Actual inability to produce enough milk is rare, with studies showing that mothers from developing countries experiencing nutritional hardship still produce amounts of milk of similar quality to that of mothers in developed countries.[8] 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 estrogen-containing hormonal contraceptives), 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.
The amount of milk produced depends on how often the mother is nursing and/or pumping; the more the mother nurses her baby, or pumps, the more milk is produced.[9][10][11][12][13] 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[14] ("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.
| Fat | |
| total (g/100 ml) | 4.2 |
| fatty acids - length 8C (% ) | trace |
| polyunsaturated fatty acids (%) | 14 |
| Protein (g/100 ml) | |
| total | 1.1 |
| casein 0.4 | 0.3 |
| a-lactalbumin | 0.3 |
| lactoferrin | 0.2 |
| IgA | 0.1 |
| IgG | 0.001 |
| lysozyme | 0.05 |
| serum albumin | 0.05 |
| ß-lactoglobulin | - |
| Carbohydrate (g/100 ml) | |
| lactose | 7 |
| oligosaccharides | 0.5 |
| Minerals (g/100 ml) | |
| calcium | 0.03 |
| phosphorus | 0.014 |
| sodium | 0.015 |
| potassium | 0.055 |
| chlorine | 0.043 |
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.
During the first few days after delivery, the breasts produce colostrum. This is a thin yellowish fluid that is the same fluid that leaks from the breasts during pregnancy. It is rich in protein and antibodies that provide passive immunity to the baby (the baby's immune system is not fully developed at birth). Colostrum also helps the newborn's digestive system to grow and function properly.
After 3 to 4 days, breasts will begin producing milk that is thin, watery, and sweet. This quenches the baby's thirst and provides the proteins, sugar, and minerals that the baby needs. Over time, the milk changes and becomes thick and creamy. This satisfies the baby's hunger.[16]
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.
The level of Immunoglobilin A (IgA) in breast milk remains high from day 10 until at least 7.5 months post-partum.[17]
Human milk contains 0.8% to 0.9% protein, 4.5% fat, 7.1% carbohydrates, and 0.2% ash (minerals).[18] Carbohydrates are mainly lactose; several lactose-based oligosaccharides have been identified as minor components. The fat fraction contains specific triglycerides of palmitic and oleic acid (O-P-O triglycerides), and also quite a large quantity of lipids with trans bonds (see: trans fat) that are considered to have a health benefit. They are vaccenic acid, and Conjugated linoleic acid (CLA) accounting for up to 6% of the human milk fat.[19][20]
The principal proteins are casein (homologous to bovine beta-casein), alpha-lactalbumin, lactoferrin, IgA, lysozyme, and serum albumin. In an acidic environment such as the stomach, alpha-lactalbumin unfolds into a different form and binds oleic acid to form a complex called HAMLET that kills tumor cells. This is thought to contribute to the protection of breastfed babies against cancer.[21]
Non-protein nitrogen-containing compounds, making up 25% of the milk's nitrogen, include urea, uric acid, creatine, creatinine, amino acids, and nucleotides.[22][23] Breast milk has circadian variations; some of the nucleotides are more commonly produced during the night, others during the day.[24]
Mother's milk has been shown to supply a type of endocannabinoid (the natural neurotransmitters that marijuana simulates), 2-Arachidonoyl glycerol.[25]
Though it now is almost universally prescribed, in some countries 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 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 breast milk is individualized, as the mother, through her touching and taking care of the baby, comes into contact with pathogens that colonize the baby, and, as a consequence, her body makes the appropriate antibodies and immune cells. This is the reason why breast milk contains very little iron, as iron is an essential precursor to the activation of micro-bacteria and gut flora; providing iron in the milk would lead to infection. However, the internal iron supplies of the infant, held in the hepatic cells of the liver, are exhausted at 4–6 months, hence this is the time that complimentary feeding is introduced, as to prevent anaemia (recommended by WHO).
Women 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 that do not breastfeed use infant formula, but breast milk donated by volunteers to human milk banks can be obtained by prescription in some countries.[26]
Expressed breast milk can be stored for later use. It is recommended that the milk is stored in hard-sided containers with airtight seals. Some plastic bags specifically manufactured for the storage of expressed breast milk are designed for storage periods of less than 72 hours - others can be used for up to 6 months if frozen.[27] The amount of time that it can be safely stored for use by infants in a home-based situation is given in this table.[28]
| Place of storage | Temperature | Maximum storage time | |
|---|---|---|---|
| In a room | 25°C | 77°F | Six to eight hours |
| Insulated thermal bag with ice packs | Up to 24 hours | ||
| In a refrigerator | 4°C | 39°F | Up to five days |
| Freezer compartment inside a refrigerator | -15°C | 5°F | Two weeks |
| A combined refrigerator and freezer with separate doors | -18°C | 0°F | Three to six months |
| Chest or upright manual defrost deep freezer | -20°C | -4°F | Six to twelve months |
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.
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.[29] 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 cow's milk proteins.[30] These problems can also affect infant formulas derived from cow's milk.
Assertions that breast milk consumption is of benefit to adult humans are questionable because many of its components undergo digestion in the adult stomach, including antibodies and other proteins.
In addition to providing essential nourishment to infants, human milk; i.e., breast milk, has a number of valuable uses, especially medicinal uses, for both children and adults. It has been used medicinally for thousands of years.[31] The antibacterial and healing properties of breast milk are often overlooked, even by the nursing mothers themselves.[32] Breast milk contains strong antibodies and antitoxins that many people believe promote healing and better overall health. However, breast milk lacks sterile and antiseptic properties if a nursing mother is infected with certain communicable diseases, such as HIV and various bacterial infections like Group B streptococcus, as breast milk can transmit such diseases to infants and other people.[33]
Breast milk has been used as a home remedy for minor ailments, such as conjunctivitis, insect bites and stings, contact dermatitis, and infected wounds, burns, and abrasions. Breast milk has also been used alternatively to boost the immune system of ill persons having viral gastroenteritis, influenza, the common cold, pneumonia, etc., because of its immunologic properties. However, breast milk should never be seen or construed as a "cure-all". Some medical experts are convinced that breast milk can induce apoptosis in some types of cancer cells. However, more research and evidence are needed in this area of cancer treatment.[34]
A minority of people, including restaurateur Hans Lochen of Switzerland and restaurateur Daniel Angerer of Austria, who operates a restaurant in New York City, have used human breast milk, or at least advocated its use, as a substitute for cow's milk in dairy products and food recipes.[35][36] Tammy Frissell-Deppe, a family counselor specialized in attachment parenting, published a book, titled A Breastfeeding Mother's Secret Recipes, providing a lengthy compilation of detailed food and beverage recipes containing human breast milk.[37] The animal rights organization known as PETA ignited a firestorm of criticism when it urged a dairy company to replace the cow's milk they use in their ice cream products with human breast milk as a way to stop cattle abuse.[38][39] Human breast milk is not produced or distributed industrially or commercially, because the use of human breast milk as an adult food is considered unusual to the majority of civilized cultures around the world, and most disapprove of such a practice.[40]
Attempts to formulate soap from breast milk have also been made, and those using it claim that its effectiveness as a cleanser is greater than, or equal to, that of traditional soaps.[41]
Despite the risk of substances transmitting from the mother to the child through breast milk, breastfeeding has far more advantages than infant formulas, and, with few exceptions, the WHO recommends exclusive breastfeeding for the first 6 months of life.[42]
The milk-producing cells are most permeable to drugs during the first postpartum week.[43]
Drug characteristics that increase excretion in milk include:[43]
Drugs are transferred from blood plasma across ductal cells to the milk by diffusion or active transport. The latter may result in higher concentration of the drug in the breast milk than in the plasma of the mother.[43]
The amounts of most drugs in milk do not exceed 2% of the total ingested dose.[43]
Environmental pollutants found in breast milk are usually not harmful, and should be considered only when environmental levels are unusually high. In addition, there has been a decrease in environmental levels, also resulting in a decrease breast-milk levels. Pollutants that are of most concern are pesticides, organic mercury, and lead. DDT and dieldrin are unavoidable, and can also be detected in infant formulas.[44] Pesticides and other toxic substances bioaccumulate; i.e., creatures higher up the food chain will store more of them in their body fat. This is an issue in particular for the Inuit, whose traditional diet is predominantly meat. Studies are looking at the effects of polychlorinated biphenyls and persistent organic pollutants in the body; the breast milk of Inuit mothers is extraordinarily high in toxic compounds.[45]
Spanish king Alfonso XIII visited the region of Las Hurdes in 1922 in order to display the concern of the crown. The king and his retinue lived in military tents planted near the town of Casares de las Hurdes. During the king's visit, a strange incident took place: A local village chief, concerned that the king was drinking only black coffee (a consequence of the king's aides distrusting the quality of the local milk owing to unsanitary conditions in the area), served the king a small jug of milk saying, "Your Majesty rest assured that this milk is totally trustworthy,"[46] which turned out to be breast milk from his wife who had recently given birth. The king became aware of this fact only after having had his café con leche.[47]
Preliminary research indicates that breast milk can induce apoptosis in some types of cancer cells.[34] Adults with GI disorders and organ donation recipients can also benefit from the immunologic powers of human breast milk.
In Costa Rica, there have been trials to produce cheese and custard from human milk as an alternative to weaning.[48]
A controversial Swiss restaurateur has created a menu based around foods cooked in human breast milk.[49]
An Icecreamists in London's Covent Garden started selling an ice cream named Baby Gaga in February 2011. Each serving costs £14. All the milk was donated by Mrs Hiley who earns £15 for every 10 ounces and calls it a "great recession beater".[50] The ice cream sold out on its first day. Despite the success of the new flavour, the Westminster Council officers removed the product from the menu to make sure that it was, as they said, "fit for human consumption", disregarding the obvious fact that breast milk is fit for, at least, human baby consumption.[51]