In my initial reading on the controversial science topic of ‘raw’ milk (debate, consumption, movement), the risk of contracting food-borne pathogenic bacteria featured prominently. In one of my first posts on the ‘raw’ milk controversy – Raw Milk & Pasteurisation, I posed a few questions that I wished to answer. Until now I haven’t delved too deep into these questions (I briefly touched on the risk of contracting a food-borne illness from consuming ‘raw’ milk in my post – Risk Assessment of ‘Raw’ Cow Milk in Australia last week). These unanswered questions are –
- If ‘raw’ milk is unpasteurised, are pathogenic bacteria such as Campylobacter jejuni, Salmonella species and Escherichia coli (E. coli) present in ‘raw’ milk?
- And what risk does drinking ‘raw’ milk pose?
- Are you likely to suffer food poisoning from drinking ‘raw’ milk?
Pathogenic bacteria isolated from ‘raw’ milk may include Salmonella species Campylobacter species, Listeria monocytogenes and E.coli, aetiological agents of gastroenteritis and more serious complications such Haemolytic Uremic Syndrome (which can lead to kidney failure) and Guillian-Barre Syndrome (a form of flaccid paralysis) (CDC, 2014a and Foodsafety.gov).
The Centers of Disease Control (2014) states that individuals are 150 more times likely to contract a food-borne illness from ‘raw’ milk than pasteurised milk. Unpasteurised milk results in 13 times more hospitalisations than illnesses involving pasteurised dairy products.
In a epidemiological study of disease outbreaks contracted from unpasteurised dairy products from 1993 to 2006 (Nonpasteurised Dairy Products, Disease Outbreaks, and State Laws – United States, 1993 – 2006), the CDC reported that of 121 outbreaks due to dairy products reported to the CDC, 73 (60%) outbreaks were caused by ‘raw’ milk (CDC, 2014b). To directly quote the CDC –
“Probably no more than 1% of the milk consumed in the United States is raw, yet more outbreaks were caused by raw milk than by pasteurised milk. If you consider the number of outbreaks caused by raw milk in light of the very small amount of milk that is consumed raw, the risk of outbreaks caused by raw milk is at least 150 times greater than the risk of outbreaks caused by pasteurised milk.”
The CDC also reported in this article that the hospitalisation rate for patients in outbreaks caused by raw milk was 13 times higher (13% vs. 1%) than the rate for people in outbreaks caused by pasteurised milk, likely due to outbreaks from ‘raw’ milk being caused by bacteria that cause more severe illnesses, such as E. coli o157:H7 (CDC, 2014b).
As a follow on from the CDC report described above, James Andrews at Food Safety News reported in 2012 that – “Since January 2007, the end of the study’s review window, there have been at least 56 additional food-borne illness outbreaks associated with raw milk. Between 2010 and 2011, raw dairy products were linked to 21 outbreaks and 201 illnesses, while pasteurised dairy products caused two outbreaks and 39 illnesses.”
‘Raw’ dairy products are linked to more food-borne illness outbreaks than pasteurised dairy products. And only a small proportion of the United States population consumes ‘raw’ dairy products. How do the numbers of food-borne illness outbreaks linked to dairy products (pasteurised and unpasteurised) compare to those caused by other food sources such as poultry, beef, shellfish and vegetables?
A CDC report on food-borne disease outbreaks in the United States from 1998 to 2008 by Gould et al, 2013 (Surveillance for Foodborne Disease Outbreaks — United States, 1998–2008, summarised on the Surveillance for Foodborne Disease Outbreaks – United States, 1998-2008 webpage) reported that the most common commodities implicated in food-borne illness outbreaks for which a food vehicle could be assigned (3,264 outbreaks) were poultry (19%), fish (19%) and beef (12%). Dairy products (presumably pasteurised and unpasteurised (‘raw’) dairy products) were implicated in about 6% of outbreaks (Gould et al, 2013). The percentage of outbreaks associated with dairy products increased from 4% of outbreaks in 1998 – 1999 to 7% during 2006 – 2008 (CDC, 2013). Interestingly, the CDC states that the increase in the number of outbreaks caused by dairy products is due to an increase in the number of outbreaks caused by unpasteurised (‘raw’) milk (CDC, 2013).
The CDC, on the website summarising the surveillance report, reports states that “leafy vegetables, poultry, beef, and foods in the category that contains fruits and nuts were responsible for the most outbreak-associated illnesses.” In the surveillance report itself, Gould et al state that dairy products (and other food commodities such as fruits/nuts and vine-stalk vegetables) contribute to a relatively larger percentage of illnesses than outbreaks, and based on the percentage of outbreak-related illnesses associated with each commodity, analysis attributed the majority of foodborne illnesses to leafy vegetables, dairy, fruits/nuts, and poultry.
In conclusion, according to CDC statistics, someone is a lot more likely to contract a food-borne illness (caused by pathogenic bacteria such as E. coli, Campylobacter or Salmonella species) from unpasteurised (‘raw’) dairy products, than pasteurised dairy products.
Dear readers, would you drink ‘raw’ milk given these statistics?
Andrews, James (2012). CDC: Raw Milk Much More Likely to Cause Illness. Food Safety News. Retrieved 26 October 2014 from http://www.foodsafetynews.com/2012/02/cdc-raw-milk-much-more-likely-to-cause-illness/#.VExl4r7N78s
Centers for Disease Control. (2013). Surveillance for Foodborne Disease Outbreaks – United States, 1998-2008. Retrieved 26 October 2014 from http://www.cdc.gov/foodsafety/fdoss/data/annual-summaries/mmwr-questions-and-answers-1998-2008.html
CDC report summarised by CDC 2013 – Gould, L. H., Walsh, K. A., Vieira, A. R., Herman, K., Williams, I. T., Hall, A. J. & Cole, D. (2013). Surveillance for Foodborne Disease Outbreaks — United States, 1998–2008. Surveillance Summaries. 62(SS01), 1-34. Retrieved 26 October 2014 from http://www.cdc.gov/mmwr/preview/mmwrhtml/ss6202a1.htm?s_cid=ss6202a1_w
Centers for Disease Control. (2014a). Raw Milk Questions and Answers. Retrieved 21 August 2014 from http://www.cdc.gov/foodsafety/rawmilk/raw-milk-questions-and-answers.html,
Centers for Disease Control. (2014b). Nonpasteurized Disease Outbreaks, 1993-2006. Retrieved 26 October 2014 from http://www.cdc.gov/foodsafety/rawmilk/nonpasteurized-outbreaks.html