Pasteurization kills bacteria | Raw milk supporters claim pasteurization reduces nutrition
GUELPH, Ont. — Much is known about the risk of consuming raw milk and raw milk products, but far less is known about their health benefits.
Both were discussed at the Science to Policy: Raw Milk Case Study symposium held in Guelph April 22.
“We need to establish some sort of legislative framework around it so the risks are minimized,” said Jeroen Douwes of the Centre for Health Research in New Zealand.
“The majority of studies show that there is a protection (against asthma and allergies), but there are simply not enough studies to show that’s conclusive.”
Sylvie Turgeon, a professor of food science with Université Laval, brought what may be considered the conventional view on raw milk: it’s not all that different from its pasteurized cousin.
“From a scientific view, pasteurization has a very minor impact on nutritional properties … but still, we cannot say that there is no change at all,” Turgeon said.
That falls in line with the position of the Centre for Disease Control in the United States:
“There are no health benefits from drinking raw milk that cannot be obtained from drinking pasteurized milk that is free of disease-causing bacteria. The process of pasteurization of milk has never been found to be the cause of chronic diseases, allergies or the developmental or behavioural problems.”
However, Douwes, pointed to about 12 studies that show raw milk may well have benefits.
“Studies in farm children suggest that raw milk may be protective against allergies and asthma independent of other farm exposures, although evidence has not always been consistent,” Douwes said.
“One study also suggests that raw milk may be protective in non-farmers’ children and adults, but the effects were limited only to atopy and rhinitis.”
Nadine Ijaz, a University of Toronto grad student, has come to similar conclusions through her personal interest in the potential for raw milk health benefits.
She said the suggestion that raw milk prevents asthma and allergies in school-aged children is “well evidenced” while enhanced immunity in newborn children, whether raw milk is consumed by the infant or the mother, is “moderately evidenced.”
Ijaz also talked about raw milk from a risk assessment perspective. She said there is evidence that demonstrates a greater risk from eating home-cooked chicken or leafy green vegetables.
“In a lot of North American literature, there seems to be an emphasis to produce zero risk with raw milk,” she said. “Pathogen prevalence data is actually not a good way to assess risk, although it is a good starting point. There have indeed been hospitalizations associated with raw milk, but to my knowledge there have been no deaths.”
She said raw milk does contain pathogens, but the accumulation is not great enough to cause illness when properly managed.
However, risk may well increase with storage and transport, she added. The maxim, “the further from the farm, the greater the risk,” was something with which others at the symposium also agreed.
Wendie Claeys of Belgium’s Agency for the Safety of the Food Chain said the background flora in raw milk provides a buffering effect against pathogenic organisms.
Like Ijaz, she said today’s biggest concerns are salmonella, campylobacter and human pathogenic E. coli. Contracting brucellosis or tuberculosis from raw milk, which was the main danger a century ago, is remote, she added.
“These milk-borne diseases have been eradicated in most developed countries.”
Raw milk is sold legally in Belgium, including through a small number of vending machines.
Claeys said pasteurization results in a commercial sterile product without a substantial loss of nutritional value or other benefits. Her agency recommended heating raw milk to the point of boiling before drinking it.
The Canadian government’s position on raw milk is similar to Belgium’s, other than the fact that raw milk sales are allowed in Belgium and most other EU countries.
Jeff Farber, Health Canada’s director of the Bureau of Microbial Hazards, cited a statement made last year by Food Standards Australia New Zealand: “FSANZ completed an extensive risk assessment of raw cow’s milk and concluded that the risk to the public is too high to change current processing requirements. The evidence shows that even extremely good hygiene procedures cannot ensure the absence of dangerous pathogens in raw milk.”
Farber also referred to the Centre for Disease Control study, which concluded that the rate of outbreaks caused by unpasteurized milk and milk products was 150 times greater than outbreaks linked to pasteurized milk.