By Lorrie Baumann
If you’re an average American, your risk of getting a serious case of listeriosis from eating one serving of a soft-ripened cheese like a brie or Camembert is about one in 8.6 billion if the cheese was made from pasteurized milk and about one in 5.5 million if the cheese was made from raw milk. To put those numbers into perspective, National Geographic estimates your chances of being struck by lightning as about 1 in 3,000 over your lifetime. Your chances of dying in an airline crash are around one in 11 million, according to a 2006 estimate published in the International Business Times.
The risks of eating brie are outlined in a report from the U.S. Food and Drug Administration’s Center for Food Safety and Applied Nutrition that was released on August 4. The study was conducted jointly with Health Canada, which used its own data to come up with considerably lower risks for Canadians. Their risk of developing a serious case of listeriosis from a serving of pasteurized cheese was one in 7.3 billion and one in 105 million for raw milk cheese. The report assumes the definition of a “serving” as an amount corresponding to how much a person might be likely to eat in a single day.
That’s a risk that’s 157 times higher for a serving of a raw milk cheese over the risk of a pasteurized milk cheese in the U.S. and a 69 times higher risk in Canada. “The point was to ask the question about whether there’s any difference,” says Dr. Catherine Donnelly, a scientist at the University of Vermont who’s been studying Listeria monocytogenes for the past 32 years. “The risk assessment concludes that yes, there is more of a risk.”
The difference in the risk according to whether you’re eating cheese in the U.S. or in Canada may have a lot to do with the fact that the Canadian study looked at reported cases of listeriosis from 2004 through mid-2009, while the FDA looked at data from 1986 to 2008. Including data from as far back as the 1980s could indicate a higher risk because it includes people who got sick from cheese made under different conditions than are usual today, according to Donnelly. “This suggests an assumption that there have been no improvements in our ability to deal with Listeria since the 1980s,” she said. “We’ve learned a lot about Listeria in the last 30 years.”
The risks of listeriosis from soft-ripened cheeses are much higher if you’re pregnant, elderly or have a compromised immune system. According to the FDA report, the risk of getting listeriosis in the U.S. from a serving of brie made from pasteurized milk is one in 136 million for the elderly, one in 55 million for a pregnant woman and one in 193 million for someone with a compromised immune system. For a cheese made from raw milk, the risk is one in 1.2 million for the elderly, one in 570,000 for a pregnant woman and one in 1.2 million for someone with a compromised immune system.
“The big concern is invasive listeriosis. The report shows that, for communities at high risk, their risk if they eat raw milk cheese is much higher than if they were to eat pasteurized milk cheese,” said Carlos Yescas, Director of the Oldways Cheese Coalition.
According to the FDA study, an elderly person who eats a serving of raw milk cheese rather than a pasteurized milk cheese increases the risk of developing invasive listeriosis by 112 times. The risk is 96 times higher for a pregnant woman and 157 times higher for someone with a compromised immune system.
“This doesn’t tells us the absolute risk of pasteurized milk cheese,” Yescas said. “That risk is not zero.”
Donnelly noted that the data from recent outbreaks of Listeria in the U.S. suggests that the elderly may be much more susceptible to listeriosis than had been previously thought. “That issue might need revisiting, as some of these latest outbreaks suggest that some of these elderly populations might be much more sensitive to lower doses of listeria,” she said. “That remains in question.”
The report notes that in the U.S. from 1986 to 2008, there were a total of 137 recalls of various types of cheeses, of which 108 were related to Listeria. There were 15 cheese recalls in Canada from 2004 through mid-2009, of which 11 were related to Listeria. While the report notes that most cases of listeriosis occur as isolated instances, there have been 14 outbreaks of Listeria in the U.S. between 1985 and 2013. They resulted in a total of 270 illnesses and 66 deaths. Of those instances, 14 outbreaks, nine were caused by Mexican-style cheeses, including queso fresco, queso cotija and asadero; one was caused by a chive cheese, one by a blue-veined aged cheese, one by ricotta and one by a soft-ripened cheese. This risk assessment considers only the risks of brie and Camembert.
Donnelly suggested that, in limiting its study to only brie and Camembert-type cheese consumption in the U.S. and Canada, the FDA may be ignoring valuable information developed in other countries with similarly sophisticated food safety science around cheeses made in other styles. “The concern is, say, French Roquefort, raw milk cheese. Different countries look at different categories differently,” she said. “Australia did a very lengthy risk assessment concluding that the level of risk for Roquefort was similar to pasteurized milk, and so they allow its importation into Australia.”
Overall, the risk of developing listeriosis from any kind of cheese is much less than the chance of contracting a foodborne illness from other foods, according to Donnelly. “Produce is the product sector that’s causing most of our foodborne illness outbreaks, which raises the question about, for our most susceptible populations, do we get rid of fresh produce? And does that spread to other populations? Fresh fruits and vegetables are not sterile food products, so what do we do about that?” she asked. “If I were running a nursing home, I’d be buying pasteurized eggs. If I were eating breakfast with my family, I’d be eating regular eggs.”