Raw milk is collected from farms daily or every other day and taken to dairies by tanker for processing. On arrival, it is subjected to various tests and, once given the all-clear, is stored and cooled at a temperature of
6 degrees C or less.
Drinking milk is heat-treated to make the raw milk bacteriologically safe and to increase its shelf life. This includes pasteurization, sterilization and UHT (ultra-high temperature). Most of the milk sold in the UK is pasteurized.
After pasteurization, milk is separated into different sorts of products. A large centrifuge, making around 7000 rotations per minute, separates the cream from the rest of the milk, leaving the skim-skimmed milk. Whole milk and semi-skimmed milk are produced by automatically blending the cream back into the skim to produce a product of the required fat content. All products are standardized: whole milk is 3.5-per-cent fat; semi-skimmed is 1.7-per-cent fat; skimmed milk is 0.1-per-cent fat. Excess cream is used to make ice cream and butter.
When milk is separated, it's normal practice to homogenize it, breaking up and dispersing the milk fat throughout the milk to create a smoother, more uniform texture. Most whole milk is homogenized to prevent the cream from rising to the top.
The milk is heated again to a temperature of about 72 degrees C, then immediately cooled and stored, ready to be packaged and delivered to shops and supermarkets.
Not just a glass of goodness
Removing the fat is not the only danger of today's milk. The average glass of commercial milk can contain:
- Hormones and growth factors. Pennsylvania State University endocrinologist Clark Grosvenor did an extensive review of some of the known bioactive hormones and growth factors found in a typical glass of milk in the US. The list included seven pituitary hormones, seven steroid hormones, seven hypothalamic hormones, eight gastrointestinal peptides (chains of two or more amino acids), six thyroid/parathyroid hormones, 11 growth factors and nine other biologically active compounds (Endocr Rev, 1993; 14: 710-28).
- Pus cells. UK cows suffer from a range of infectious diseases, includ-ing brucellosis, bovine tuberculosis, foot-and-mouth disease, viral pneumonia and Johne's disease. The cow responds to infection by generating white blood cells. These, along with cellular debris and dead tissue-in fact, pus-are excreted into the milk. According to the EU's 1995 Dairy Products (Hygiene) Regulations, the white cell limit is 400,000 cells/mL in bulk milk. This means that milk containing up to 400 million pus cells/L can be legally sold for human consumption (Butler J. White Lies. The health consequences of consuming cow's milk. Bristol: Vegetarian & Vegan Foundation, 2006).
- Antibiotics. Sickly cows also mean a constant supply of antibiotics. One study found antibiotic-resistant strains of Salmonella as a result of antibiotic use in cattle (N Engl J Med, 2000; 342: 1242-9).
- Recombinant bovine somatotropin (rBST). In 1994, the US Food and Drug Administration (FDA) approved the use of this genetically engineered hormone in cows to increase milk production. Milk from cows treated with rBST contains elevated levels of insulin-like growth factor 1 (IGF-1), which is linked to certain cancers (Int J Health Serv, 1996; 26: 173-85). What's more, rBST-treated cows have more infections and so are given more antibiotics-and higher amounts of these drugs, as well as pus and bacteria, are found in their milk.
Do we need milk at all?
Milk is touted as a great natural source of calcium, and we are told to eat plenty of calcium to prevent osteoporosis, or thinning of the bones. But eating dairy products can increase the rate at which calcium is lost from the body and so hasten osteoporosis.
As well as being high in calcium, dairy products are also high-protein foods. Too much protein in the diet-whether from milk products or any other source, such as meat, fish or eggs-means that the body has to get rid of the excess. To do this, the kidneys work to clear the excess-and also lose calcium, in a process known as 'protein-induced hypercalciuria'.
Indeed, a recent meta-analysis found that a low intake of milk was not associated with any important increase in fracture risk in either men or women (Osteoporos Int, 2005; 16: 799-804). Likewise, the Boston-based Nurses' Health Study, which has followed more than 80,000 women for 12 years, could find no protective effect of increased milk consumption on the risk of bone fractures (Am J Public Health, 1997; 87: 992-70).
A better way to build healthy bones is with weight-bearing exercise (J Bone Miner Res, 1995; 10: 1068-75), getting adequate sunlight (around 15 minutes a day) and increasing your intake of leafy green vegetables, which contain calcium as well as vitamin K, an essential factor in bone metabolism (see WDDTY vol 17 no 4).