Whether urban legends, deceptive marketing, or beliefs held by raw milk proponents under a siege mentality, there are more microbiological and nutritional myths about raw milk than nearly any other food.
After reviewing the myths, I looked for information from scientists and consumer advocates and busted the Top Ten 21st Century Raw Milk Myths. Here are the results:
Myth #1. Raw milk has been consumed for thousands of years without a problem.
This myth reflects a lack of understanding about the historical impact of infectious diseases transmitted by raw milk for centuries, especially tuberculosis, brucellosis (undulant fever), and scarlet fever (1-5). Raw milk has caused numerous deaths of infants throughout history. Pasteurization was developed to prevent these well-documented illnesses and deaths from contaminated raw milk. In developed countries, the use of pasteurization has been directly correlated to reduced infant mortality (6). In developing countries today, from India to Africa, raw milk is routinely boiled before being fed to babies, children, and other family members to protect them from deadly milk-borne infections.
Myth #2. Pasteurization destroys all the nutrients in milk.
Since the dawn of pasteurization (using heat to kill pathogens), this myth has prevailed without scientific evidence. When pasteurization started to become more mainstream early last century, some people were suspicious of the technology. Subsequent analyses of the nutritional components of raw and pasteurized milk revealed no significant differences for the major nutritional components such as proteins, carbohydrates, and vitamins (7-10). View comparison of raw and pasteurized organic whole milk labels:
Myth #3. Homogenization produces dangerous changes in milk.
This is another old myth dating back to the first years of milk processing during the last century. Homogenization is simply the process of physically breaking up the fat globules in cow’s milk to make a “homogenous” fluid milk beverage (11-12). Unhomogenized cows milk will develop a cream layer at the top of the container. Goat’s milk is “naturally homogenized” and does not form a cream layer during storage. There is no proven health difference between mechanically homogenized cow’s milk and naturally homogenized goat’s milk.
Myth #4. Raw milk kills pathogens.
This myth evolved from a partial truth based on experimental data where researchers inoculated “bad” bacteria into raw milk and measured its survival. In one experiment, a few strains of the bacteria Campylobacter died sooner in raw milk compared with sterile milk (13), but most strains survived long in enough in both types of milk to make someone sick. Other experiments have shown survival and even growth of E. coli O157, Salmonella, and Listeria in raw milk and raw milk products (14-17). Live bacterial pathogens are routinely found in bulk tank milk on farms, which proves that “bad” bacteria are not reliably killed by “good” bacteria, enzymes or other components of raw milk (18-21). Raw milk also does not kill or reduce foodborne viruses or parasites.
Myth #5. It is safe to leave raw milk at room temperature.
This myth appears to come from a revival in the interest in traditional diets and practices. Clabbered milk is raw milk allowed to naturally sour and thicken (22). The raw milk is allowed to warm, which can be very dangerous if the milk was accidently contaminated with pathogenic bacteria that grow at warm temperature (e.g., Salmonella, E. coli O157, Staphylococcus aureus). Bacterial pathogens thrive on the nutrients in fresh milk and can outgrow the “good bacteria” once given the advantage of increased temperature. Not all raw milk contains pathogens, but because you can’t see or smell them, there is no way to know if it is safe to take this chance. A safer alternative is to buy cultured dairy products such as buttermilk, yogurt, and kefir made with pasteurized milk. View charts of pathogen growth from experiments conducted at room temperature and under refrigeration:
Myth #6. Raw milk is healthier than pasteurized milk for babies.
Raw milk activists in developed countries, especially the United States, mostly perpetuate this myth. In contrast, most parents in developing countries recognize the dangers of raw animal milk and boil milk to destroy pathogens before feeding to babies or young children. Numerous studies show that breastfeeding is the healthiest option for infants (23). A human mother’s milk is designed to be the best source of nutrition and immune-giving factors for her baby. When breastfeeding is not an option, there is nearly unanimous agreement in the medical and public health communities worldwide that only pasteurized animal milk should be given to infants and young children (1-2, 24).
Myth #7. Millions of people purchase raw milk every year in the United States.
This myth appeared recently in an intense marketing campaign by raw milk advocates. Their estimate is based on a 2007 CDC FoodNet survey that found ~3% of people surveyed in 10 states reported drinking raw milk in the last 7 days (25). The survey did not differentiate between raw milk consumed on the farm vs. purchased by a customer. Most raw milk is consumed by rural dairy farm families and their workers who drink raw milk directly from their own animals (26-27). Estimates of non-farm, urban and suburban consumers who purchase raw milk from stores or farmers markets are drastically lower compared with farm family consumption. Commercial raw milk sales make up less
than 1% of milk sales overall (28). Retail commercial raw milk is a highly specialized niche product that is legal in only a few states and sold mostly in small natural food stores and co-ops. Major retailers do not sell raw milk because of the well-documented food safety risks. Whole Foods discontinued sales of raw milk in 2010 due to liability concerns (29).
Myth #8. Deaths attributed to drinking raw milk were from “bathtub cheese” and factory farms, not legal or “certified” raw milk.
This myth goes back to at least the 1980s when a single certified raw milk dairy in California was ultimately shut down after numerous illnesses and deaths from Salmonella Dublin (30). These deaths included immunosuppressed persons with AIDS, a then newly recognized syndrome. From 1980-1983, 15 deaths from salmonellosis in California from certified raw milk were documented (31). Stricter federal regulations were put in place during the 1980s to curb the high rate of illnesses and deaths from legal raw milk (4). There are also documented deaths from listeriosis and salmonellosis due to contaminated Mexican-style cheese (e.g., queso fresco) made with raw milk, and processed milk contaminated after pasteurization (32-33). No deaths in the last decade have been attributed to legal raw milk, but E. coli O157:H7 infections and hemolytic uremic syndrome (HUS) cases have been linked to a number of pasture-based raw milk farms and herdshares in states where raw milk sales are legal (34-36). Advances in medical treatment of HUS likely prevented death, although some patients may suffer from permanent kidney damage and other chronic health problems caused by the original E. coli O157 infection.
Myth #9. European researchers recommend raw milk for treatment of child allergies.
This myth originates from large population-based studies of rural farm factors that affect allergic and other conditions in Europe. A correlation between drinking farm milk and reduced childhood allergies has been found in epidemiological studies (37-41). However, the authors admit that causation has not been proven, and it is unclear if farm (unboiled) milk or other farm factors such as being around animals and barns influence the development of allergies in children. The European researchers recommend that raw milk not be used as a “treatment” for childhood allergies due to the risk of pathogens and serious infection.
Myth #10. Pathogens only come from factory farms (“confined feeding animal operations” or CAFOs).
This myth blossomed after publication of a small study in 1998 that showed a possible relationship between grain feeding and E. coli carriage in cattle (42). This lead to a widespread unsubstantiated belief that a grain diet (typical of a feedlot) affects the acidity of the stomach and promotes the growth of E. coli O157:H7. There is still much more research needed to understand how diet affects an animal’s likelihood of shedding pathogens in their feces (43-50). Higher rates of carriage have been found on feedlots where animals are crowded and when high rations of distiller’s grains are fed, but the specific influence of feed remains unclear. Furthermore, pathogens have been found in the guts and feces of cattle and other animals (including free-roaming wildlife) living on pasture with no exposure to grain. See the types of farms linked to recent dairy outbreaks.
References
1. Jaros, P., N. Cogger and N. French. 2008. A systematic review of the human disease evidence associated with the consumption of raw milk and raw milk cheeses. A report prepared for the New Zealand Food Safety Authority (NZFSA). Available at: http://www.nzfsa.govt.nz/science/research-projects/final-report-rawmilk.pdf
2. World Health Organization. Populations at Risk, page 3. Available at: http://www.who.int/foodsafety/publications/general/en/fos_brochure1999_2en.pdf
3. Kaplan, M.M., M. Abdussalam, and G. Bilgona. Diseases transmitted through milk. Available at: http://whqlibdoc.who.int/monograph/WHO_MONO_48_%28p11%29.pdf
4. Weisbecker, A. 2007. A legal history of raw milk in the United States. J Environ Health 69. Available at: http://www.marlerclark.com/pdfs/raw-milk-jeh.pdf
5. Steele, J. H. 2000. History, trends, and extent of pasteurization. J Am Vet Med Assoc 217:175-8.
6. Warriner, K. 2011. Raw Milk: Political Football or Food Safety Issue. Raw milk webinar Sept2011
7. Nestle, M. Safe Food: The Politics of Food Safety. Berkeley: University of California Press, 2010. Available at: http://www.marlerclark.com/pdfs/SafeFood_Excerpt.pdf
8. Macdonald, L. E., J. Brett, D. Kelton, S. E. Majowicz, K. Snedeker, and J. M. Sargeant. 2011. A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes. J Food Prot 74:1814-32.
9. Bell, R.W. The effect of heat on the solubility of the calcium and phosphorus compounds in milk. The Journal of Biological Chemistry. 1925;64(2):391-400.
10. Potter, M. E., A. F. Kaufmann, P. A. Blake, and R. A. Feldman. 1985. Unpasteurized milk. The hazards of a health fetish. JAMA 252:2048-52.
11. Homogenization of milk and milk products. Guelph University. Available at: http://www.foodsci.uoguelph.ca/dairyedu/homogenization.html
12. Homogenizers and homogenizations. Ohio State University. Available at: http://class.fst.ohio-state.edu/Dairy_Tech/10.0%20Homogenization.htm
13. Doyle, M. P., and D. J. Roman. 1982. Prevalence and survival of Campylobacter jejuni in unpasteurized milk. Appl Environ Microbiol 44:1154-8.
14. Massa, S., E. Goffredo, C. Altieri, and K. Natola. 1999. Fate of Escherichia coli O157:H7 in unpasteurized milk stored at 8 degrees C. Lett Appl Microbiol 28:89-92.
15. Wang, G. T. Zhao, and M. P. Doyle. 1997. Survival and growth of Escherichia coli O157:H7 in unpasteurized and pasteurized milk. J Food Protect 60:610-3.
16.
Marth, E. H. 1969. Salmonellae and salmonellosis associated with milk and milk products. A review. J Dairy Sci 52:283-315.
17. Rose, A. 2009. Does raw milk kill pathogens? A visual summary of the research on competitive exclusion. Available at: http://rawmilkwhitepapers.com/
18. Jayarao, B. M., and D. R. Henning. 2001. Prevalence of foodborne pathogens in bulk tank milk. J Dairy Sci 84:2157-62.
19. Karns, J. S., J. S. Van Kessel, B. J. McCluskey, and M. L. Perdue. 2005. Prevalence of Salmonella enterica in bulk tank milk from US dairies as determined by polymerase chain reaction. J Dairy Sci 88:3475-9.
20. Oliver, S. P., B. M. Jayarao, and R. A. Almeida.2005. Foodborne pathogens in milk and the dairy farm environment: food safety and public health implications. Foodborne Pathog Dis 2:115-29.
21. Van Kessel, J. S., J. S. Karns, L. Gorski, B. J. McCluskey, and M. L. Perdue. 2004. Prevalence of Salmonellae, Listeria monocytogenes, and fecal coliforms in bulk tank milk on US dairies. J Dairy Sci
22. What is clabbered milk? Available at: http://www.wisegeek.com/what-is-clabbered-milk.htm
23. Hanson, L. A. 2004. Immunobiology of Human Milk: How Breastfeeding Protects Babies. Pharmasoft Publishing.
24. Advice 15-2011 of the Scientific Committee of the FASFC on the risk-benefit evaluation of raw cow milk consumption and the effect of heat treatment on these risks and benefits.
2011. Available at: http://www.afsca.be/comitescientifique/avis/_documents/AVIS15-2011_FR_DOSSIER2010-25.pdf
25. CDC. 2011. FoodNet Population Survey: Atlas of Exposures, 2006-2007. Centers for Disease Control and Prevention, Available at: http://www.cdc.gov/foodnet/surveys/FNExpAtl03022011.pdf.
26. Jayarao, B. M., S. C. Donaldson, B. A. Straley, A. A. Sawant, N. V. Hegde, and J. L. Brown. 2006. A survey of foodborne pathogens in bulk tank milk and raw milk consumption among farm families in Pennsylvania. J. Dairy Sci. 89:2451-2458.
27. Hoe, F. G., and P. L. Ruegg. 2006. Opinions and practices of Wisconsin dairy producers about biosecurity and animal well-being. J. Dairy Sci. 89:2297-2308.
28. Headrick, M. L., S. Korangy, N. H. Bean, F. J. Angulo, S. F. Altekruse, M. E. Potter, and K. C. Klontz. 1998. The epidemiology of raw milk-associated foodborne disease outbreaks reported in the United States, 1973 through 1992. Am J Public Health 88:1219-21.
29. Beecher, C. Whole Foods Pulls raw milk in 4 states. 2010. Food Safety News. Available at: https://www.foodsafetynews.com/2010/03/whole-foods-pulls-raw-milk-in-4-states/
30. Werner, S. B., G. L. Humphrey, and K. I. Kamei. 1979. Association between raw milk and human Salmonella Dublin infection. BMJ 2:238-41.
31. Richwald, G. A., S. Greenland, B. J. Johnson, J. M. Friedland, E. J. C. Goldstein, and D. T. Plichta. 1988. Assessment of the excess risk of Salmonella Dublin infection associated with the use of certified raw milk. Public Health Rep 103:489-93.
32. CDC. OutbreakNet. Foodborne Outbreak Online Database. Available from: http://www.cdc.gov/foodborneoutbreaks/Default.aspx
33. CDC. 2008. Outbreak of Listeria monocytogenes infections associated with pasteurized milk from a local dairy–Massachusetts, 2007. MMWR Morb Mortal Wkly Rep 57:1097-100.
34. CDC. Escherichia coli O157:H7 infection associated with drinking raw milk–Washington and Oregon, November-December 2005. MMWR Morb Mortal Wkly Rep 2007;56:165-167.
35. CDC. Escherichia coli O157:H7 infections in children associated with raw milk and raw colostrum from cows–California, 2006. MMWR Morb Mortal Wkly Rep 2008;57:625-628.
36. Guh, A., Q. Phan, R. Nelson, K. Purviance, E. Milardo, S. Kinney, P. Mshar, W. Kasacek, and M. Cartter. 2010. Outbreak of Escherichia coli O157 associated with raw milk, Connecticut, 2008. Clin Infect Dis 51:1411-7.
37. Kilpelainen, M., E. O. Terho, H. Helenius, and M. Koskenvuo. 2000. Farm environment in childhood prevents the development of allergies. Clin Exp Allergy 30:201-8.
38. Perkin, M. R., and D. P. Strachan. 2006. Which aspects of the farming lifestyle explain the inverse association with childhood allergy? J Allergy Clin Immunol 117:1374-81.
39. Waser, M., K. B. Michels, C. Bieli, H. Floistrup, G. Pershagen, E. von Mutius, M. Ege, J. Riedler, D. Schram-Bijkerk, B. Brunekreef, M. van Hage, R. Lauener, and C. Braun-Fahrlander. 2007. Inverse association of farm milk consumption with asthma and allergy in rural and suburban populations across Europe. Clin Exp Allergy 37:661-70.
40. Braun-Fahrlander, C., and E. von Mutius. 2011. Can farm milk consumption prevent allergic diseases? Clin Exp Allergy 41:29-35.
41. Loss, G., S. Apprich, M. Waser, W. Kneifel, J. Genuneit, G. Buchele, J. Weber, B. Sozanska, H. Danielewicz, E. Horak, R. J. van Neerven, D. Heederik, P. C. Lorenzen, E. von Mutius, and C. Braun-Fahrlander. 2011. The protective effect of farm milk consumption on childhood asthma and atopy: the GABRIELA study. J Allergy Clin Immunol 128:766-773 e4.
42. Diez-Gonzalez, F., T. R. Callaway, M. G. Kizoulis, and J. B. Russell. 1998. Grain feeding and the dissemination of acid-resistant Escherichia coli from cattle. Science 281:1666-8.
43. Callaway, T. R., R. O. Elder, J. E. Keen, R. C. Anderson, and D. J. Nisbet. 2003. Forage feeding to reduce preharvest Escherichia coli populations in cattle, a review. J Dairy Sci 86:852-60.
44. Callaway, T. R., M. A. Carr, T. S. Edrington, R. C. Anderson, and D. J. N
isbet. 2009. Diet, Escherichia coli O157:H7, and cattle: a review after 10 years. Curr Issues Mol Biol 11:67-79.
45. Fegan, N., P. Vanderlinde, G. Higgs, and P. Desmarchelier. 2004. The prevalence and concentration of Escherichia coli O157 in faeces of cattle from different production systems at slaughter. J Appl Microbiol 97:362-70.
46. Gilbert, R. A., S. E. Denman, J. Padmanabha, N. Fegan, D. Al Ajmi, and C. S. McSweeney. 2008. Effect of diet on the concentration of complex Shiga toxin-producing Escherichia coli and EHEC virulence genes in bovine faeces, hide and carcass. Int J Food Microbiol 121:208-16.
47. Gilbert, R. A., N. Tomkins, J. Padmanabha, J. M. Gough, D. O. Krause, and C. S. McSweeney. 2005. Effect of finishing diets on Escherichia coli populations and prevalence of enterohaemorrhagic E. coli virulence genes in cattle faeces. J Appl Microbiol 99:885-94.
48. Grauke, L. J., S. A. Wynia, H. Q. Sheng, J. W. Yoon, C. J. Williams, C. W. Hunt, and C. J. Hovde. 2003. Acid resistance of Escherichia coli O157:H7 from the gastrointestinal tract of cattle fed hay or grain. Vet Microbiol 95:211-25.
49. Krueger, N. A., R. C. Anderson, W. K. Krueger, W. J. Horne, I. V. Wesley, T. R. Callaway, T. S. Edrington, G. E. Carstens, R. B. Harvey, and D. J. Nisbet. 2008. Prevalence and Concentration of Campylobacter in Rumen Contents and Feces in Pasture and Feedlot-Fed Cattle. Foodborne Pathog Dis.
50. Wells, J. E., S. D. Shackelford, E. D. Berry, N. Kalchayanand, J. M. Bosilevac, and T. L. Wheeler. 2011. Impact of reducing the level of wet distillers grains fed to cattle prior to harvest on prevalence and levels of Escherichia coli O157:H7 in feces and on hides. J Food Prot 74:1611-7.
———————-
Michele Jay-Russell, DVM, PhD is a researcher at the Western Institute for Food Safety and Security, University of California, Davis. Prior to joining the university, she worked as an epidemiologist with the California Department of Public Health.