What is milk?
Milk is the nutrient fluid produced by the mammary glands of female mammals. The female ability to produce milk is one of the defining characteristics of mammals. It provides the primary source of nutrition for newborns before they are able to digest more diverse foods. The early lactation milk is known as colostrum, and carries the mother’s antibodies to the baby. It can reduce the risk of many diseases in both the mother and baby.
The exact components of milk vary by species, but it contains significant amounts of saturated fat, vitamins (A, D, E, Riboflavin, etc), sugar (lactose), proteins (casein, albumin, etc) and calcium. Aquatic mammals, such as seals and whales, produce milk that is very rich in fats and other solid nutrients when compared with land mammals’ milk.
Humans, like other mammals, can consume mother’s milk during their infancy. In many ethnic groups, people lose the ability to digest milk after childhood (that is, they become lactose intolerant), so many traditional cuisines around the world do not feature dairy products. On the other hand, those cultures that do tolerate milk have often exercised great creativity in using the milk of domesticated ruminants, especially cows, but also sheep, goats, yaks, water buffalo, horses and camels. For millenia, cow’s milk has been processed into dairy products such as cream, butter, yogurt, ice cream, and especially the storable and transportable cheese. Industrial science has brought us casein, whey protein, lactose, condensed milk, powdered milk, and many other food-additive and industrial products.
Human milk is fed to infants through breastfeeding, either directly or by expressing the milk to be stored and consumed later.
The term milk is also used for non-animal substitutes such as soy milk, rice milk, almond milk, and coconut milk, and even the regurgitated substance pigeons feed their young, called crop milk, which bears little resemblance to mammalian milk.
Milk began containing differing amounts of fat during the 1950’s. 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.
- 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.
Cow milk (whole) Nutritional value per 100 g
Energy 60 kcal 250 kJ
|100 g corresponds to 103 ml.
Percentages are relative to US
recommendations for adults.
Source: USDA Nutrient database
Comercial milk is often pasteurizad and homogenized before packaging.
Pasteurization consists in heating milk for a very short period of time and cooling it very fast, in order to kill many harmful micro organisms but not to destroy many valuable nutrients. Pasteurized milk is still perishable and must be stored cold by both suppliers and consumers. Dairies print expiration dates on each container, after which stores will remove any unsold milk from their shelves. In many countries it is illegal to sell milk that is not pasteurized.
Upon standing for 12 to 24 hours, fresh milk has a tendency to separate into a high-fat cream layer on top of a larger, low-fat milk layer. The cream is often sold as a separate product with its own uses; today the separation of the cream from the milk is usually accomplished rapidly in centrifugal cream separators. The fat globules rise to the top of a container of milk because fat is less dense than water. The smaller the globules, the more other molecular-level forces prevent this from happening. In fact, the cream rises in cow milk much quicker than a simple model would predict: rather than isolated globules, the fat in the milk tends to form into clusters containing about a million globules, held together by a number of minor whey proteins (McGee 19). These clusters rise faster than individual globules can. The fat globules in milk from goats, sheep, and water buffalo do not form clusters as readily and are smaller to begin with; cream is very slow to separate from these milks.
Milk is often homogenized, a treatment which prevents a cream layer from separating out of the milk. The milk is pumped at high pressures through very narrow tubes, breaking up the fat globules through turbulence and cavitation.  A greater number of smaller particles possess more total surface area than a smaller number of larger ones, and the original fat globule membranes cannot completely cover them. Casein micelles are attracted to the newly-exposed fat surfaces; nearly one-third of the micelles in the milk end up participating in this new membrane structure. The casein weighs down the globules and interferes with the clustering that accelerated separation. The exposed fat globules are briefly vulnerable to certain enzymes present in milk, which could break down the fats and produce rancid flavors. To prevent this, the enzymes are inactivated by pasteurizing the milk immediately before or during homogenization. Homogenized milk tastes blander but feels creamier in the mouth than unhomogenized; it is whiter and more resistant to developing off flavors. Creamline, or cream-top, milk is unhomogenized; it may or may not have been pasteurized.
Many people are against the use of commercial milk, and instead they urge encourage people to drink what it’s called “real milk”, also known as raw milk.
Here are some of it’s advantages:
The source of most commercial milk is the modern Holstein, bred to produce huge quantities of milk three times as much as the old-fashioned cow. She needs special feeding and antibiotics to keep her well. Her milk contains high levels of growth hormone from her pituitary gland, even when she is spared the indignities of genetically engineered Bovine Growth Hormone to push her to the udder limits of milk production.
Real food for cows is green grass in Spring, Summer and Fall; green food, silage, hay and root vegetables in Winter. It is not soy meal, cottonseed meal or other commercial feeds, nor is it bakery waste, chicken manure or citrus peel cake, laced with pesticides. Vital nutrients like vitamins A and D, and the “Price Factor” (a fat-soluble catalyst that promotes optimum mineral assimilation) are greatest in milk from cows eating green grass, especially rapidly growing green grass in the spring and fall. Vitamins A and D are greatly diminished, and the Price Factor disappears, when milk cows are fed commercial food. Soy meal has the wrong protein profile for the dairy cow, resulting in a short burst of high milk production followed by premature death. Most milk (even most milk labeled “organic”) comes from dairy cows that are kept in confinement their entire lives and never see green grass!
Pasteurization destroys enzymes, diminishes vitamin content, denatures fragile milk proteins, destroys vitamins C, B12 and B6, kills beneficial bacteria, promotes pathogens and is associated with allergies, increased tooth decay, colic in infants, growth problems in children, osteoporosis, arthritis, heart disease and cancer. Calves fed pasteurized milk do poorly and many die before maturity. Raw milk sours naturally but pasteurized milk turns putrid; processors must remove slime and pus from pasteurized milk by a process of centrifugal clarification. Inspection of dairy herds for disease is not required for pasteurized milk. Pasteurization was instituted in the 1920s to combat TB, infant diarrhea, undulant fever and other diseases caused by poor animal nutrition and dirty production methods. But times have changed and modern stainless steel tanks, milking machines, refrigerated trucks and inspection methods make pasteurization absolutely unnecessary for public protection. And pasteurization does not always kill the bacteria for Johne’s disease suspected of causing Crohn’s disease in humans with which most confinement cows are infected. Much commercial milk is now ultra-pasteurized to get rid of heat-resistant bacteria and give it a longer shelf life. Ultra-pasteurization is a violent process that takes milk from a chilled temperature to above the boiling point in less than two seconds. Clean raw milk from certified healthy cows is available commercially in several states and may be bought directly from the farm in many more.
Homogenization is a process that breaks down butterfat globules so they do not rise to the top. Homogenized milk has been linked to heart disease.
Fat is not that bad
Average butterfat content from old-fashioned cows at the turn of the century was over 4% (or more than 50% of calories). Today butterfat comprises less than 3% (or less than 35% of calories). Worse, consumers have been duped into believing that low-fat and skim milk products are good for them. Only by marketing low-fat and skim milk as a health food can the modern dairy industry get rid of its excess poor-quality, low-fat milk from modern high-production herds. Butterfat contains vitamins A and D needed for assimilation of calcium and protein in the water fraction of the milk. Without them protein and calcium are more difficult to utilize and possibly toxic. Butterfat is rich in short- and medium chain fatty acids which protect against disease and stimulate the immune system. It contains glyco-spingolipids which prevent intestinal distress and conjugated linoleic acid which has strong anticancer properties.
Powdered skim milk, a source of dangerous oxidized cholesterol and neurotoxic amino acids, is added to 1% and 2% milk. Low-fat yogurts and sour creams contain mucopolysaccharide slime to give them body. Pale butter from hay-fed cows contains colorings to make it look like vitamin-rich butter from grass-fed cows. Bioengineered enzymes are used in large-scale cheese production. Many mass produced cheeses contain additives and colorings and imitation cheese products contain vegetable oils.
Help small farmers
Pasteurization laws favor large, industrialized dairy operations and squeeze out small farmers. When farmers have the right to sell unprocessed milk to consumers, they can make a decent living, even with small herds.