A business expert I worked with some years ago while writing a book about business planning used to remark, “If you don’t know where you are going, any path will take you there.” 


I feel a little like I’m descending further into that Alice-in-Wonderland kind of place with this food-borne illness data situation. I described in my previous post how disturbing the quality and accessibility of the food-borne illness data are. I referred in that post to my frustration in being able to locate data used by a new study published in the Journal of Food Protection to suggest that pasteurized milk becomes extremely dangerous for listeria when pasteurized at higher than standard temperatures. That study indicated that 18 people die each year from regularly pasteurized listeria-contaminated milk, and that the number could go up by a factor of 40 if higher temperatures were used in pasteurization. 


How did the authors determine, as their starting point, that 18 people die each year from listeria in milk, when the data compiled by the U.S. Centers for Disease Control show nine people died from pasteurized milk in total since 1998 (and only three of those nine died from listeriosis in fluid milk; the other six died from tainted cheese), and no deaths from listeria in raw milk? The authors’ source wasn’t clear in the actual paper (I have a copy of the full study but am not able to publish it here because it is copyright protected.)


So I inquired with the lead author, Matthew Stasiewicz, who is a Ph.D. candidate at Cornell University in food science. I finally heard back from him yesterday, and he said the data came from a 2003 study compiled by the U.S. Food and Drug Administration, with the sexy title, “Listeria monocytogenes Risk Assessment”. 


Typical of FDA risk assessments, this study is highly technical with lots of complex mathematical modeling exploring “what if” scenarios.  Another way to describe it: murky.


My immediate question was about the origin of the statement that 18 people die from listeriosis in milk each year. And I have to say, I still don’t know. Here is how the FDA study, which is about “ready-to-eat foods” in 23 categories, summarizes its data sources: 


“The published scientific literature, government food intake surveys, health statistics, epidemiological information, unpublished food product surveys acquired from state and federal public health officials and trade associations, and surveys specifically designed to augment the data available for the risk assessment are the primary sources of data used in this document. Expert advice on scientific assumptions was actively sought from leading scientists from academia, industry, and government. This included two formal reviews of the underlying model structure and assumptions by the United States National Advisory Committee on Microbiological Criteria for Foods. In addition, the risk assessment was initially published in draft form and public comments sought for six months.”


And there, deep in the bowels of this lengthy report, in Appendix 10, Table 4, you will see the 18 deaths estimated from listeria in pasteurized milk; unpasteurized milk, according to the table, is responsible for less than one death per year–0.6 deaths, which I presume means that roughly one person has died every two years from raw milk. Perfectly obvious—I’m surprised everyone wasn’t aware of this data. 

(As an aside, I have yet to find a single documented illness, let alone a death, from listeria monocytogenes in fluid raw milk in the last ten years. I know listeria m has been found in raw milk, and dairies have been shut down as a result, but no one has become sick from it, that I am aware of. )


Now that they have their baseline of 18 deaths a year, the authors of this study speculate that ever more use of ultra-high-temperature pasteurization may already be leading to increases in listeriosis. “Evidence of the ill effects of this processing change may be hidden in the epidemiologic record,” the authors say in their discussion. “Although the public health data are certainly not conclusive, further investigation is needed to determine whether changing the pasteurization of fluid milk has affected the epidemiology of listeriosis in the United States and the EU.” 


Ah, yes, more funding needed for a problem no one even knew existed, and now is “documented” based on hocus-pocus estimates. 

Maybe these authors should explore whether there is an inverse relationship between heat and listeriosis; the fact that raw milk is never heated may help explain why no one gets listeriosis from it. Nothing doing–the authors discovered in that same 2003 risk assessment data indicating raw milk is more risky for listeriosis than normally pasteurized milk. According to Staciewicz, it shows that “the per annum risk cases of listeriosis due to all fluid milk consumption in the U.S. is 91 cases per year, a risk of 1 case per billion servings. Please note the relatively greater risk per serving of unpasteurized fluid milk, 7 cases per billion servings.”  Where that 2003 study came up with the number of servings of raw milk will have to be a research project for me for another time, I’m afraid.  


In the end, we don’t know how close to reality the data about illnesses and deaths from listeria in pasteurized milk (or unpasteurized milk) really are. Even if they bear a relationship to reality, they are already eleven years old. And I’m not convinced they bear much relationship to reality since, as we saw in the last post, the real data on food-borne illness is likely incomplete, and the huge numbers of estimated data are likely highly exaggerated for political purposes. 


I am no apologist for pasteurized milk—I suspect many of the serious nutritional benefits are wrung out via pasteurization and homogenization. That being said, I have no more desire to unjustly demonize pasteurized milk as a frequent carrier of serious pathogens than I do raw milk. I have as much trouble accepting, based on the quality of data used here, the notion that higher temperature heated milk is 40 times more dangerous than standard pasteurized milk as I do accepting that raw milk is 150 times more dangerous than pasteurized or that soft raw milk cheeses are 60-150 times more dangerous than pasteurized ones, or that 20,000-plus Minnesota raw milk drinkers get sick from tainted milk each year.  It makes for good headlines, but in the end, dangerous headlines because they are such misleading headlines. Indeed, I would go so far as to suggest that such “risk analysis” is fundamentally fraudulent. 

As I said at the start of this post, if you don’t know where you are going, any path will take you there. It seems increasingly apparent that if you want to demonize particular foods, there is data somewhere in the vast federal trove that will help you make your case. Just get me out of the sink hole.