Nutrition and health

The composition of milk differs widely between species. Factors such as the type of protein; the proportion of protein, fat, and sugar; the levels of various vitamins and minerals; and the size of the butterfat globules and the strength of the curd are among those than can vary.Introduction to Dairy Science and Technology, webpage of University of Guelph For example:

• Human milk contains, on average, 1.1% protein, 4.2% fat, 7.0% lactose (a sugar), and supplies 72 kcal of energy per 100 grams.
• Cow's milk contains, on average, 3.4% protein, 3.6% fat, and 4.6% lactose, and supplies 66 kcal of energy per 100 grams. See also Nutritional benefits further on.

Nutritional benefits

Milk began containing differing amounts of fat during the 1950s. A serving (1 cup or 250 ml) of 2%-fat milk contains 285 mg of calcium, which represents 22% to 29% of the daily recommended intake (DRI) of calcium for an adult. Depending on the age, 8 grams of protein, and a number of other nutrients (either naturally or through fortification):

• Vitamins D and K are essential for bone health.
• Iodine is a mineral essential for thyroid function.
• Vitamin B12 and riboflavin are necessary for cardiovascular health and energy production, and B12 is difficult to get outside of animal products or else as supplemental pills.
• Biotin and pantothenic acid are B vitamins important for energy production.
• Vitamin A is critical for immune function.
• Potassium and magnesium are for cardiovascular health.
• Selenium is a cancer-preventive trace mineral.
• Thiamine is a B-vitamin important for cognitive function, especially memory
• Conjugated linoleic acid is a beneficial fatty acid that inhibits several types of cancer in mice, it has been shown to kill human skin cancer, colorectal cancer and breast cancer cells in vitro studies, and may help lower cholesterol and prevent atherosclerosis; only available in milk from grass-fed cows.

Studies show possible links between low-fat milk consumption and reduced risk of arterial hypertension, coronary heart disease, and obesity. Overweight individuals who drink milk may benefit from decreased risk of insulin resistance and type 2 diabetes.^[8]

Nutritional/physiological detriments

The following additional issues are often cited as warranting consideration:

• Lactose intolerance, discussed below.
• Milk that has not received a fat content reduction is rich in saturated fat and cholesterol, which numerous sources have suggested as contributing to an increased risk of atherosclerosis and coronary heart disease when consumed in excessive quantity. Low-fat and non-fat forms of milk may mitigate this risk^{[citation needed}].
• Cow milk allergy (CMA) is as an immunologically mediated adverse reaction to one or more cow's milk proteins. Rarely is it severe enough to cause death.
• Milk from contaminated or heavily polluted areas can contain high levels of toxic compounds that have bioaccumulated into it. The nuclear power plant disaster at Chernobyl in Ukraine spread a cloud of radioactivity that ended up in the milk supply and many animals had to simply be killed. The contamination spread across many areas of Europe and affected the dairy industries and even milk as far away as the United States had detectable levels of contamination. As well through the principle of bioaccumulation, herbicides and pesticides can accumulate in milk, and organic milk produced without chemicals has become one of the most popular organic products that people choose.
• Milk contains varying levels of white blood cells, depending upon the health of the source animals; controversy surrounds whether these are simply somatic cells or, in an alternate form, pus.^[9] In the United States, one to seven drops of these cells are in every eight-ounce glass of milk, varying by state, according to guidelines set up by the Food and Drug Administration and statistics reported by the dairy industry.^[10] Only one state out of all fifty, Hawaii, has a cell count lower than the dairy industry's recommendations; seventeen states produce milk that would be illegal to sell based on somatic cell limits in Europe.
• Since November 1993, with FDA approval, Monsanto has been selling recombinant bovine somatotropin (rbST)--or rBGH--to dairy farmers. Bovine growth hormone is administered to cattle in order to increase their milk production, though the hormone also naturally fosters liver production of insulin-like growth factor 1 (IGF1). The deposit, thereof, in the milk of rBGH-affected cattle has been the source of concern, however all milk contains IGF1. The IGF1 in milk from rBGH-affected cattle does not vary from the range normally found in a non-supplemented cow. Elevated levels of IGF1 in human blood has been linked to increased rates of breast, colon, and prostate cancer by stimulating their growth,^[11][12] though this has not been linked to milk consumption. The EU has recommended against Monsanto milk.^[13] In addition, the cows frequently contract an udder infection known as mastitis, partly responsible for the aforementioned prevalence of blood cells in dairy products.^[14] Milk from rBGH-affected cattle is banned in Canada, Australia, New Zealand, and Japan due to the mastitis problems. On June 9, 2006 the largest milk processor in the world and the two largest supermarkets in the United States--Dean Foods, Wal-Mart, and Kroger--announced that they are "on a nationwide search for rBGH-free milk [1]."
• Several sources suggest a correlation between high calcium intake (2000 mg per day, or twice the US recommended daily allowance, equivalent to six or more glasses of milk per day) and prostate cancer.^[15] A large study specifically implicates dairy.^[16] A review published by the World Cancer Research Fund and the American Institute for Cancer Research states that at least eleven human population studies have linked excessive dairy product consumption and prostate cancer,^{[citation needed}] however randomized clinical trial data with appropriate controls only exists for calcium, not dairy produce, where there was no correlation.^[17]
• There is some debate concerning the amount of calcium from milk that is actually absorbed by the human body. ^[18]

Lactose intolerance

Lactose is a simple sugar that is present in all milk of the species of origin, and is digested with the help of the enzyme lactase. The production of this enzyme declines significantly after weaning in all mammals, including human beings. Lactose intolerance is the condition in which lactase is not produced in adulthood. With lactose intolerance, the result of consuming too much lactose is excess gas production and often diarrhea. Lactose-intolerant adults can drink about a cup (250 ml or 8 oz) of milk per day without severe symptoms.

Most adults in the world are lactose-intolerant (McGee 14: "lactose tolerant adults are a distinct minority on the planet"). Lactose-intolerant adults stop producing significant amounts of lactase sometime between the ages of two and five. A relatively recent genetic change caused some populations (McGee 14: "several thousand years ago"), including many Northern Europeans, to continue producing lactase into adulthood.

Common Misconceptions

A recent study failed to demonstrate a correlation between milk consumption and production of mucus by respiratory mucosa in healthy adults.^[19]

Nutrition - comparison by animal source

Milk Composition Analysis, per 100 grams

Source: McCane, Widdowson, Scherz, Kloos.[2]

Wikipedia

http://en.wikipedia.org/w/index.php?title=Milk&action=history

http://www.gnu.org/copyleft/fdl.html