Tuesday, March 31, 2009

Raw milk - not the 'cure-all' it's propounded to be

It wasn't much fun being a dairy lover back in the late 19th and early 20th century. Although heating or boiling milk before it was fed to infants was known to reduce the incidence of disease and mortality, milk products were the cause of 25% of all cases of food and waterborne illnesses traced to source (1).

Luckily for us, in 1864 Louis Pasteur developed the process now known as pasteurization. Pasteurization involves heating milk to 161°F (71.7°C) for 15 seconds, performing the dual function of killing milk-borne pathogens and extending the time that milk stays fresh. Michigan was the first state to make milk pasteurization mandatory in 1947, and nowadays, the incidence of food-borne disease from milk products is <1%>

All sectors of animal agriculture are currently plagued by small but extremely vocal minorities, with enough spare disposable income to buy products that they perceive as being healthier, less-processed, locally-grown, environmentally-friendlier or more sustainable than conventional food products. The emphasis here is on the word 'small' - it's a niche market of customers for whom giving a child a twinkie rather than a macrobiotic whole-grain carob rice cake could be considered child abuse. However, it's a form of food elitism that's increasingly finding its way into the mainstream media (3).

So what claims are the granola-brigade making this time? The main claim appears to be that valuable nutrients are destroyed by pasteurization. According to one raw milk enthusiast via Twitter, pasteurized milk is 'dead'. The 'facts' (according to the raw milk lobby) suggest that raw milk contains proteins, vitamins, minerals, anti-cancer agents (conjugated linoleic acid) and a whole host of goodies (4), whereas pasteurized milk is a chemical soup of hormones (5) and saturated fats. Not surprisingly, this is nonsense propagated by non-scientists: no scientific, peer-reviewed study has shown any difference in nutritional value or composition between pasteurized and raw milk (6, 7).

However, there is one major difference between pasteurized and unpasteurized milk consumption: the incidence of foodborne disease. The presence of foodborne pathogens in raw milk samples has been documented by several studies including that of Jayaro et al. (8), who found Salmonella isolates in 6% of samples, Shiga toxin-producing E. coli in 2.4% of samples and Listeria monocytogenes in 2.8% of samples. In another study investigating E. coli outbreaks after raw milk consumption, Keene (9) concludes that "consumption of raw milk is a high-risk behavior and will continue to cause morbidity and mortality until people stop consuming raw milk and raw milk products". Finally, Gillespie et al. (10) reports that between 1992-2000, 52% of foodborne outbreaks in England and Wales were attributed to raw milk consumption.

More information on the risks of raw milk consumption is available from the US Food and Drug Administration here: http://www.fda.gov/bbs/topics/NEWS/2007/NEW01576.html and here: http://www.foodsafety.gov/~dms/rawmilk.html

I have no issue with people doing things that endanger their health. Want to drive without a seat-belt? Fine. Want to smoke 45 cigarettes per day? Go for it. Want to help yourself to a tasty cold beverage that has a 6% chance of containing Salmonella? Yummy. However, it should be a choice made based on science and relative risk. I lived on a dairy farm for ten years where everyone drank raw milk. Did anyone get ill? No. Were we all likely to be more resistant to the bugs found on dairy farms through working with the animals every day? Yes. Would I give raw milk to a child or immunosuppressed person? Not on your (their) life.

Milk is milk. Just make sure that the choices you make are informed by science, not granola.

(Endnote: One other intriguing claim is that raw milk was used to 'cure' illnesses from ~460 BC until WWII (3), the same period when, for example, trepanning (drilling holes in the skull to release evil spirits) was used to 'cure' epilepsy. Think the FDA might want to check the
efficaciousness claims for this one.)


(1) http://www.milkfacts.info/Milk%20Processing/Heat%20Treatments%20and%20Pasteurization.htm#PastHist

(2) Schmidt, R. H. and P. M. Davidson. 2008. Milk Pasteurization and the Consumption of Raw Milk in the United States. Food Protection Trends. Jan 2008. 45-47.

(3) http://lifestyle.msn.com/your-life/living-green/articlegreenchan.aspx?cp-documentid=18708415&gt1=45002

(4) http://www.raw-milk-facts.com/raw_milk_health_benefits.html

(5) http://www.realmilk.com/

(6) Potter, M. E. et al. 1984. Unpasteurized milk: The hazards of a health fetish. Journal of the American Medical Association. 252:2048–2052.

(7) LeJeune, J. T. and J. P. Rajala-Schultz. 2009. Unpasteurized milk: A continued public health threat. Food Safety. 48:93-100.

(8) Jayaro, B. M. et al. 2006. A survey of foodborne pathogens in bulk tank milk and raw milk consumption among farm families in Pennsylvania. Journal of Dairy Science 89:2451-2458.

(9) Keene, W. E. et al. 1997. A prolonged outbreak of Escherichia coli O157:H7 infections caused by commercially distributed raw milk. Journal Infectious Disease. 176:815–818.

(10) Gillespie, I. A. et al. 2003. Milkborne general outbreaks of infectious intestinal disease, England and Wales, 1992–2000. Epidemiology of Infection. 130:461–468