Not since the 1940s have scientists carried out any significant research on raw cows milk, a lamentable situation attributable most probably to the influence of the powerful dairy industry. The fact that we must refer to old studies showing the safety and superior health benefits of raw milk versus pasteurized has been a source of criticism for the raw milk movement.
Fortunately, much recent research exists on the qualities of human milk, and these results are applicable to the milk of other domesticated mammals--cows, goats, sheep, camels, water buffalo and reindeer.
For many years, scientists believed that human milk was safe because it was sterile. This notion has given way to the realization that human milk contains many pathogens. For example, scientists in Finland detected several strains of Staphylococcus aureus "known as a causative agent of maternal breast infections and neonatal infections" in human breast milk samples.1 Scientists in Canada report that breast milk "is a body fluid capable of transmitting blood-borne pathogens when ingested."2 In fact, in a screening program for expressed breast milk in China, testing revealed "the alarming fact that our study group had the highest rate of contamination ever reported."3 Pathogenic bacteria in the milk included enterococci and Staphylococcus aureus. The research team speculated that the high rate of contamination "could be due to the Chinese tradition of avoiding bathing for one month after childbirth." Pathogens are transferred to the suckling infant via breast milk from the skin.
The discovery of pathogens in human milk has coincided with the discovery of multiple, redundant anti-microbial mechanisms in the milk of all mammals, which protect the infant by building immunity and by binding or destroying pathogens. "Protective factors in milk can target multiple early steps in pathogen replication and target each step with more than one antimicrobial compound. The antimicrobial activity in human milk results from protective factors working not only individually but also additively and synergistically."4
These protective factors include immunoglobulins, mucins, lactoferrin, lactoperoxidase, oligosaccharides and short- and medium-chain fatty acids.
Compounds containing a sugar molecule, such as glycoconjugates and oligosaccharides, are synthesized by the mammary gland. They protect the nursing infant by inhibiting pathogen binding. These compounds are specific to different pathogens. For example, "a fucosyloligosaccharide inhibits infection by Campylobacter jejuni. Binding of Streptococcus pneumoniae and of enteropathogenic E. coli to their respective receptors is inhibited by human milk oligosaccharides. The 46-kD glycoprotein, lactadherin, inhibits rotavirus binding and infectivity. . . a mannosylated glycopeptide inhibits binding by enterohemorrhagic E. coli. A glycosaminoglycan inhibits binding of gp120 to DC4, the first step in HIV infection."5
The protective factors in milk inhibit not only the currently present pathogens but also "anticipate new mutations and new pathogens . . ."6 The immunological factor IgA, for example "appears to reflect long-term maternal immunologic memory."6 This explains the Chinese wisdom--shocking to investigators--of not bathing for a month after giving birth. When the infant suckles from dirty skin, the immunological factors in milk can program the infant for protection against a myriad of pathogens for life! Medical science has had the tendency to foster a man-can-do-things-better-than-nature attitude, but these studies can only inspire awe and wonder at the exquisite processes that support biological life.
The protective components in mammalian milk are mostly molecules of exceeding complexity, many of them involving protein compounds with precise but fragile folding. Heat disrupts and inactivates most of them, especially the rapid and/or prolonged heating of pasteurization.7
That heating reduces the ability of milk to protect against infections is more than just speculation. In 1984, researchers in India carried out a randomized controlled trial involving 226 high-risk newborns given combinations of formula and raw and pasteurized human milk. The highest rate of infection occured in the group given pasteurized human milk plus formula (33 percent). Those given raw human milk plus formula had a 16 percent rate of infection and those given pasteurized human milk alone had a 14.3 percent rate of infection. The lowest rate of infection was 10.5 percent in the group given raw human milk.8
Researchers in Africa looked at ways of storing human milk. No growth of pathogens was observed in raw human milk stored 4 hours at high temperature (30-38 degrees C), 8 hours at room temperature (15-27 degrees C) and 24 hours at refrigerator temperature (4-10 degrees C).9 They concluded that "although freezing temperature (0-4 degrees C) seemed safest for breast milk storage, short-term storage in a freezer is not recommended due to the likely hazards of the thawing process." Another study found that raw human milk was safe for human consumption for up to 72 hours refrigerated.10 Longer-term storage by freezing did not cause safety problems.
Unfortunately, human milk donated to breast milk banks is routinely pasteurized before freezing, thereby destroying the many protective mechanisms that human milk can confer on premature babies.
The research on human milk applies equally well to the milk of other mammals. In fact, because baby animals are born in muck and manure, the protective mechanisms in the milk of cows, goats, sheep, etc., are often even more concentrated. For example, lactoperoxidase, an enzyme in raw milk that kills pathgens using small amounts of hydrogen peroxide and free radicals, is ten times higher in goat milk than human milk!11
While research on human milk has revealed the fact that raw milk provides strong protection against disease, the bureaucrats in our US dairy and health departments are mired in 40-year-old science. Next time one of these unenlightened souls tells you that the milk you give your children has to be pasteurized for their protection, ask them whether the pathogen-loaded breast milk you give your infant has to be pasteurized, too.
- J Appl Microbiol. 2003;95(3):471-8.
- Neonatal Netw. 2000 Oct;19(7)21-5.
- J Hosp Infec. 2004 Oct;58(2):146-50.
- J Nutr. 2005 May;135(5):1286-8.
- Curr Med Chem. 1999 Feb;6(2):117-27.
- Adv Exp Med Biol. 2004;554:145-54.
- Scientific American, December 1995; Lancet. 1984 Nov 17;2(8412):111-3.
- Lancet. 1984 Nov 17;2(8412):111-3.
- Cent Afr J Med. 2000 Sep;46(9):247-51.
- Eur J Pediatr. 2000 Nov;159(11):793-7.
- J Dairy Sci 1991;74:783-787
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