The U.S. Centers for Disease Control estimates that one in six Americans, or some 48 million people, get sick each year from food-borne illness. The agency arrives at this huge number, despite the fact that only about 15,000 actual illnesses are reported to the CDC by state health agencies, by using “under-diagnosis multipliers” and various other mathematical modeling.

Since it began doing such estimates in 1999 (when it estimated 76 million people get sick, then revised the number down to 48 million in 2011), the media have accepted the numbers, and used them as facts rather than estimates.

While the large estimates have been widely reported, they have only been used as theoretical numbers, and never applied to a particular food….until last month. That was when the CDC put out a study of food-borne illnesses in Minnesota, asserting that raw milk was likely responsible for many more illnesses than were officially tabulated during the decade 2001-2010.

Using unusual epidemiological methodologies, along with curious mathematical modeling and extrapolations, the CDC study reckoned there were more than 20,000 illnesses from raw milk in Minnesota, rather than the 21 that had been previously reported by public health authorities as attributable to raw milk. Quite a leap.

The study’s authors “estimated that up to 20,502 Minnesotans, or 17% of raw milk consumers, may have become ill with enteric pathogens during the study period after consuming raw milk. This finding suggests that [reported] outbreaks represent a small number of the illnesses associated with raw milk consumption and that the risk for illness associated with raw milk consumption is far greater than determined based on the occurrence of recognized outbreaks.”

How was the Minnesota Department of Health able to turn 21 reported illnesses into 20,502?

Underlying its hocus-pocus math is the questionable (and highly intentional) assumption that illnesses from raw milk are under-reported, when, in fact, illnesses from raw milk are obsessively chased down and recorded by state public health and agriculture officials, who have long advised against consuming it. When raw milk is tainted with a pathogen like campylobacter, it usually sickens a few people rather than just one, so public health officials are able to make the epidemiological inference that raw milk was likely involved.

Once they make the connection to raw milk, it is a fairly simple step to locate the producer–certainly simpler than for most other foods, since raw milk is so highly regulated that most sales are made directly from dairies to individuals, and even in places like California, which allow retail sales, there are only two or three dairies selling at retail.

There’s little of the complication as with illnesses from spinach or cantaloupes or lettuce or tacos of trying to figure out exactly which farm or food vendor the food came from. Once they have the farm in their sights, the public health or agriculture regulators then test the milk, to try to find the offending pathogen. That isn’t always successful, but for the purposes of ascribing blame (to any food), epidemiological evidence is acceptable.

In the Minnesota study, the CDC turned epidemiological methodology on its head. It went back to essentially unresolved individual cases of illnesses from pathogens over the ten years 2001-2010, and pulled out everyone who got sick from campylobacter or E.coli O157:H7 or salmonella…..and had consumed raw milk—some 530 cases. Never mind that they might have consumed other potentially dangerous foods, like chicken (which Consumer Reports recently said is nearly all tainted by pathogens or other possibly threatening bacteria), deli food (known to be risky) or fast food. If they said that raw milk was among the foods they consumed the previous week, they were assumed to have been sickened by raw milk.

But wait, there was more. The Minnesota study took the 530 newly classified cases of raw milk illnesses and applied “pathogen-specific underdiagnosis multipliers” to the numbers. These “multipliers,” of generally 30 to 100, are used to estimate illnesses from various pathogens based on the public health assumption that many illnesses go unreported, usually because the victims recover quickly enough to not even consult with a physician so as to seek a medical diagnosis.

And presto, faster than you can say “raw milk made me sick,” you’ve turned 21 illnesses into more than 20,000 illnesses that are blamed on raw milk in Minnesota from 2001 to 2010. Even after these huge leaps, the authors, apparently feeling on a roll, went even further. They concluded that, based on those 20,000-plus illnesses, that more than 17 per cent of all Minnesota raw milk drinkers got sick during the decade 2001-2010.

I have met hundreds of raw milk drinkers over the years, and I ask many of them if they have ever become ill from raw milk. Only a couple have said they have. I then ask if they know of other raw milk drinkers who have become ill, and the answer is the same—they almost never know anyone.

Needless to say, the growing legions of supporters of raw milk were outraged by the CDC Minnesota study. The Raw Milk Institute, an organization that has established safety standards for producers of raw milk, quickly issued a rebuttal, criticizing “the broad sweeping assumptions and methodologies used by the authors of the recent Minnesota Raw Milk Study.”

RAWMI also pointed to the absence of “relative risk estimates….for other potential sources of contamination such as raw eggs, produce, ground meat, etc. This makes it very hard for the reader to compare the risk estimates given for raw milk to the risk of consuming other raw or pasteurized foods.”

RAWMI also allowed that even if some of the newly categorized raw-milk illnesses in Minnesota did come from raw milk, almost half of those so designated by the CDC came from farm families or friends of farm families. These farms are generally producers of milk intended for pasteurization, not milk ordinarily made available for consumers seeking raw milk, and milk known from other studies to be tainted; conventional-milk farmers tolerate such tainting, knowing pathogens will be killed off during the pasteurization process.

No matter to the mainstream media. Places like the Los Angeles Times, NBC News, Fox News and USA Today all reported the CDC assessment of the Minnesota data as if it was fact. A few included a quote or two from raw milk proponents disputing the study’s thrust, but those weren’t played as if there truly was serious controversy.

This study is disturbing on a number of levels, but big picture, it seems to set a dangerous precedent. It represents a radical departure from past public health data analysis. Post-Minnesota-data, if you get sick from campylobacter or E.coli O157:H7 or salmonella and you have consumed raw milk, then any other culprits, like chicken or fast food, can be automatically eliminated and you can be assumed to have been sickened by raw milk.

If you carry the logic a bit further, you realize that under this new precedent, even if reported illnesses from raw milk decline to zero, the public health enforcers will be able to pull out of their hats any number of supposed illnesses from people who drank raw milk, and became sick from some other food. In other words, they’ll always be able to say raw milk is unacceptably risky, and can’t be tolerated, no matter what the facts are.