Milk Explained

Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many diseases in the baby.

Milk derived from cattle species is an important food. It has many nutrients. The precise nutrient composition of raw milk vary by species and by a number of other factors, but it contains significant amounts of saturated fat, protein and calcium as well as vitamin C. Cow's milk has a pH ranging from 6.4 to 6.8, making it slightly acidic.[1] [2]

Throughout the world, there are more than 6 billion consumers of milk and milk products, the majority of them in developing countries. Over 750 million people live within dairy farming households. World's dairy farms produced over 710 million tons of milk in 2010. India is the world's largest producer and consumer of milk, yet neither exports nor imports milk. New Zealand, EU-15 and Australia are the world's three largest exporters of milk and milk products. China, Mexico and Japan are the world's largest importers of milk and milk products. Milk is a key contributor to improving nutrition and food security particularly in developing countries. Improvements in livestock, dairy technology and milk quality may offer the most promise in reducing poverty and malnutrition in the world.[3]

Types of consumption

There are two distinct types of milk consumption: a natural source of nutrition for all infant mammals and a food product for humans of all ages that is derived from other animals.

Nutrition for infant mammals

In almost all mammals, milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later. Some cultures, historically or currently, continue to use breast milk to feed their children until they are seven years old.

Human infants sometimes are fed fresh goat milk. There are known risks in this practice, including those of developing electrolyte imbalances, metabolic acidosis, megaloblastic anemia, and a host of allergic reactions.

Food product for humans

In many cultures of the world, especially the Western world, humans continue to consume milk beyond infancy, using the milk of other animals (especially cattle, goats and sheep) as a food product. For millennia, cow's milk has been processed into dairy products such as cream, butter, yogurt, kefir, ice cream, and especially the more durable and easily transportable product, cheese. Modern industrial processes produce casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products.

Humans are an exception in the natural world for consuming milk past infancy, despite the fact that many humans show some degree (some as little as 5%) of lactose intolerance, a characteristic that is more prevalent among individuals of African or Asian descent. The sugar lactose is found only in milk, forsythia flowers, and a few tropical shrubs. The enzyme needed to digest lactose, lactase, reaches its highest levels in the small intestines after birth and then begins a slow decline unless milk is consumed regularly. On the other hand, those groups who do continue to tolerate milk often have exercised great creativity in using the milk of domesticated ungulates, not only of cattle, but also sheep, goats, yaks, water buffalo, horses, reindeers and camels. The largest producer and consumer of cattle and buffalo milk in the world is India.[4]

Top ten per capita cow's milk and cow's milk products consumers in 2006[5]
CountryMilk (liters)Cheese (kg)Butter (kg)


It was reported in 2007 that with increased worldwide prosperity and the competition of bio-fuel production for feed stocks, both the demand for and the price of milk had substantially increased worldwide. Particularly notable was the rapid increase of consumption of milk in China and the rise of the price of milk in the United States above the government subsidized price.[6] In 2010 the Department of Agriculture predicted farmers would receive an average of $1.35 per US gallon of cow's milk (35 cents per liter), which is down 30 cents per gallon from 2007 and below the break-even point for many cattle farmers.


The term milk is also used for white colored, non-animal beverages resembling milk in color and texture such as soy milk, rice milk, almond milk, and coconut milk. In addition, a substance secreted by pigeons to feed their young is called crop milk and bears some resemblance to mammalian milk. Dairy relates to milk and milk production, eg. dairy products.

Evolution of lactation

The mammary gland is thought to have been derived from apocrine skin glands.[7] It has been suggested that the original function of lactation (milk production) was keeping eggs moist. Much of the argument is based on monotremes (egg-laying mammals).[7] [8] [9] The original adaptive significance of milk secretions may have been nutrition or immunological protection. This secretion gradually became more copious and accrued nutritional complexity over evolutionary time.[7]


Humans first learned to regularly consume the milk of other mammals following the domestication of animals during the Neolithic Revolution[10] or the invention of agriculture. This development occurred independently in several places around the world from as early as 9000–7000 BC in Southwest Asia[11] to 3500–3000 BC in the Americas.[12] The most important dairy animals—cattle, sheep and goats—were first domesticated in Southwest Asia, although domestic cattle has been independently derived from wild auroch populations several times since. Initially animals were kept for meat, and archaeologist Andrew Sherratt has suggested that dairying, along with the exploitation of domestic animals for hair and labor, began much later in a separate secondary products revolution in the 4th millennium BC.[13] Sherratt's model is not supported by recent findings, based on the analysis of lipid residue in prehistoric pottery, that show that dairying was practiced in the early phases of agriculture in Southwest Asia, by at least the 7th millennium BC.[14]

From Southwest Asia domestic dairy animals spread to Europe (beginning around 7000 BC but not reaching Britain and Scandinavia until after 4000 BC),[15] and South Asia (7000–5500 BC).[16] The first farmers in central Europe[17] and Britain milked their animals. Pastoral and pastoral nomadic economies, which rely predominantly or exclusively on domestic animals and their products rather than crop farming, were developed as European farmers moved into the Pontic-Caspian steppe in the 4th millennium BC, and subsequently spread across much of the Eurasian steppe.[18] Sheep and goats were introduced to Africa from Southwest Asia, but African cattle may have been independently domesticated around 7000–6000 BC.[19] Camels, domesticated in central Arabia in the 4th millennium BC, have also been used as a dairy animal in North Africa and the Arabian peninsula. In the rest of the world (i.e., East and Southeast Asia, the Americas and Australia) milk and dairy products were historically not a large part of the diet, either because they remained populated by hunter-gatherers who did not keep animals or the local agricultural economies did not include domesticated dairy species. Milk consumption became common in these regions comparatively recently, as a consequence of European colonialism and political domination over much of the world in the last 500 years.

In 1863, French chemist and biologist Louis Pasteur invented pasteurization, a method of killing harmful bacteria in beverages and food products.[20]

In 1884, Doctor Hervey Thatcher, an American inventor from New York, invented the first glass milk bottle, called 'Thatcher's Common Sense Milk Jar', which was sealed with a waxed paper disk.[20] Later, in 1932, plastic-coated paper milk cartons were introduced commercially as a consequence of their invention by Victor W. Farris.[20]

Sources of milk

All female mammals can by definition produce milk, but cow milk dominates commercial production. Human milk is not produced or distributed industrially or commercially; however, milk banks exist that allow for the collection of donated human milk and its redistribution to infants who may benefit from human milk for various reasons (premature neonates, babies with allergies, metabolic diseases, etc.).

In the Western world, cow's milk is produced on an industrial scale and is by far the most commonly consumed form of milk. Commercial dairy farming using automated milking equipment produces the vast majority of milk in developed countries. Dairy cattle such as the Holstein have been bred selectively for increased milk production. About 90% of the dairy cows in the United States and 85% in Great Britain are Holsteins. Other dairy cows in the United States include Ayrshire, Brown Swiss, Guernsey, Jersey, and Milking Shorthorn (Dairy Shorthorn).

Sources aside from cows

Aside from cattle, many kinds of livestock provide milk used by humans for dairy products. These animals include camel, donkey, goat,horse, reindeer, sheep, water buffalo, and yak.

In Russia and Sweden, small moose dairies also exist.

According to the US National Bison Association, American bison (also called American buffalo) are not milked commercially;[21] however, various sources report cows resulting from cross-breeding bison and domestic cattle are good milk producers, and have been used both during the European settlement of North America and during the development of commercial Beefalo in the 1970s and 1980s.

Milk may also come from vegetable sources; such milk will be accessible to people who are vegans. Examples of this milk are soya milk, using soya beans; and rice milk.

Production worldwide

See main article: Dairy farming. The largest producer of dairy products and milk is India followed by the United States,[22] Germany, and Pakistan.

Increasing affluence in developing countries, as well as increased promotion of milk and milk products, has led to a rise in milk consumption in developing countries in recent years. In turn, the opportunities presented by these growing markets have attracted investment by multinational dairy firms. Nevertheless, in many countries production remains on a small scale and presents significant opportunities for diversification of income sources by small farmers.[23] Local milk collection centers, where milk is collected and chilled prior to being transferred to urban dairies, are a good example of where farmers have been able to work on a cooperative basis, particularly in countries such as India.[24]

The table below shows the numbers for water buffalo milk production. Cattle milk is produced in a much wider range.

Top ten buffalo milk producers in 2007[25] !Country!Production (tonnes)!Note
59,210,000Unofficial/Semi-official/mirror data
20,372,000official figure
2,900,000FAO estimate
958,603official figure
241,500FAO estimate
220,462official figure
200,000FAO estimate
30,375official figure


In the United States, there are two grades of milk, with Grade A primarily used for direct sales and consumption in stores, and Grade B used for indirect consumption, such as in cheese making or other processing.

The differences between the two grades are defined in the Wisconsin administrative code for Agriculture, Trade, and Consumer Protection, chapter 60.[26] Grade B generally refers to milk that is cooled in milk cans, which are immersed in a bath of cold flowing water that typically is drawn up from an underground water well rather than using mechanical refrigeration.

Notes and References

  1. William H. Bowen and Ruth A. Lawrence. Comparison of the Cariogenicity of Cola, Honey, Cattle Milk, Human Milk, and Sucrose. 10.1542/peds.2004-2462. 2005. Pediatrics. 116. 4. 921–6. 16199702.
  2. Soil pH: What it Means
  3. Web site: Status and Prospects for Smallholder Milk Production: A Global Perspective. Food and Agriculture Organization of the United Nations. 2010. Hemme and Otte.
  4. Web site: World's No 1 Milk Producer. 2010-08-28.
  5. Web site: Goff. Douglas. Introduction to Dairy Science and Technology: Milk History, Consumption, Production, and Composition. Dairy Science and Technology. University of Guelph. 8 February 2011. 2010.
  6. Wayne Arnold, "A Thirst for Milk Bred by New Wealth Sends Prices Soaring", The New York Times September 4, 2007.
  7. Oftedal. Olav T.. The mammary gland and its origin during synapsid evolution. Journal of Mammary Gland Biology and Neoplasia. 7. 3. 225–252. 2002. 10.1023/A:1022896515287. 12751889.
  8. Oftedal. Olav T.. The origin of lactation as a water source for parchment-shelled eggs. Journal of Mammary Gland Biology and Neoplasia. 7. 3. 253–66. 2002. 12751890. 10.1023/A:1022848632125.
  9. Web site: Lactating on Eggs. 2009-04-14. 2003-07-14. 2009-03-08.
  10. referring to the Neolithic period in Eurasian prehistory
  11. Book: Bellwood, Peter. First Farmers: the origins of agricultural societies. 2005. Blackwell Publushing. Malden, MA. 978-0-631-20566-1. 44–68. The Beginnings of Agriculture in Southwest Asia.
  12. Book: Bellwood, Peter. First Farmers: the origins of agricultural societies. 2005. Blackwell Publushing. Malden, MA. 978-0-631-20566-1. 146–179. Early Agriculture in the Americas.
  13. Book: Sherratt, Andrew. Pattern of the Past: Studies in honour of David Clarke. 1981. Cambridge University Press. Cambridge. 0521227631. 261–305. Hodder. I.. Isaac. G.. Hammond. N.. Plough and pastoralism: aspects of the secondary products revolution.
  14. Vigne. J.-D.. Helmer. D.. Was milk a "secondary product" in the Old World Neolithisation process? Its role in the domestication of cattle, sheep and goats. Anthropozoologica. 2007. 42. 2. 9–40.
  15. Book: Price, T. D.. Europe's First Farmers. 2000. Cambridge University Press. Cambridge. 0521662036. 1–18. T. D. Price. Europe's first farmers: an introduction.
  16. Book: Meadow, R. H.. The origins and spread of agriculture and pastoralism in Eurasia. 1996. UCL Press. London. 1857285387. 390–412. D. R. Harris. The origins and spread of agriculture and pastoralism in northwestern South Asia.
  17. Craig. Oliver E.. John Chapman, Carl Heron, Laura H. Willis, László Bartosiewicz, Gillian Taylor, Alasdair Whittle and Matthew Collins. Did the first farmers of central and eastern Europe produce dairy foods?. Antiquity. 2005. 79. 306. 882–894.
  18. Book: Anthony, D. W.. The Horse, the Wheel, and Language. 2007. Princeton University Press. Princeton, NJ. 978-0691058870.
  19. Book: Gifford-Gonzalez, D.. African archaeology: a critical introduction. 2004. Blackwell Publishing. Malden, MA. 9781405101554. 187–224. A. B. Stahl. Pastoralism and its Consequences.
  20. "The History Of Milk"
  21. Web site: About Bison: Frequently Asked Questions. National Bison Association. 2009-08-16.
  22. International dairy product prices are turning down: how far, how fast?
  23. J. Henriksen, [ "Milk for Health and Wealth".] FAO Diversification Booklet Series 6, Rome
  24. O.P. Sinha, "Dairy in India", FAO, Rome
  25. Livestock Production statistics
  26. Wisconsin administrative code for Agriculture, Trade, and Consumer Protection, Chapter ATCP 60