According to a 13-year review by the Centers for Disease Control and Prevention, the rate of outbreaks associated to pasteurized milk was 150 times less than outbreaks caused by unpasteurized milk (raw milk) and products made from it. Furthermore, the researchers found that the rate out outbreaks was over two times higher in states where the sale of unpasteurized milk was legal compared to those where it was illegal.

The study is published February 21 in the CDC journal Emerging Infectious Diseases.

The researchers examined dairy product outbreaks in all 50 states from 1993 to 2006. During the study period, the team worked out the amount of milk the U.S. produced (approximately 2.7 trillion pounds), and compared it to the amount the CDC estimates was likely consumed raw (1% or 27 billion pounds). From these figures, the researchers were able to determine that the rate for outbreaks linked to unpasteurized milk was 150 times higher. Raw milk products include yogurt and cheese.

During the study period there were 121 dairy-related disease outbreaks, which caused:

  • 239 hospitalizations
  • 4,413 illnesses
  • and 3 deaths

The researchers found that out of the 121 outbreaks 60% (73), were determined to be caused by raw milk products by state health officials. Raw milk outbreaks were responsible for 200 of the 239 hospitalizations. In addition, the team found that these outbreaks occurred in 30 states. Out of these 30 states, 55 outbreaks (75%) occurred in 21 states, where it was legal at the time to sell unpasteurized milk products. During the study period, 7 states changed their laws.

Consumers are unable to determine whether raw milk is safe to drink by tasting, smelling, or looking at it. Collecting milk introduces some bacteria, even under optimal conditions of cleanliness. Pasteurization involves heating milk in order to destroy disease-causing bacteria, in unpasteurized milk these bacteria can multiple and grow in the milk and cause sickness.

Robert Tauxe, M.D., M.P.H., deputy director of CDC’s Division of Foodborne, Waterborne and Environmental Diseases (DFWED), explained:

“This study shows an association between state laws and the number of outbreaks and illnesses from raw milk products. Restricting the sale of raw milk products is likely to reduce the number of outbreaks and can help keep people healthier. The states that allow sale of raw milk will probably continue to see outbreaks in the future.”

In addition, the researchers found that unpasteurized milk outbreaks resulted in considerably more severe illnesses, and affection more individuals under 20 years of age. The team found that in the unpasteurized milk outbreaks with known age breakdowns, 60% were younger than 20 years of age, compared to 23% of outbreaks from pasteurized products. Children are more likely to get seriously ill from the bacteria in unpasteurized milk than adults.

Co-author of the study Barbara Mahon, M.D., M.P.H., deputy chief of CDC’s DFWED Enteric Diseases Epidemiology Branch, said:

“While some people think that raw milk has more health benefits than pasteurized milk, this study shows that raw milk has great risks, especially for children, who experience more severe illnesses if they get sick. Parents who have lived through the experience of watching their child fight for their life after drinking raw milk now say that it’s just not worth the risk.”

Other key findings of the study include:

  • Often a relatively mild infection like Staphylococcus aureus or norovirus caused pasteurized milk and cheese outbreaks.
  • 1% of patients in pasteurized milk outbreaks were hospitalized compared to 13% in unpasteurized milk outbreaks. According to the researchers, this may be because all the unpasteurized milk outbreaks were caused by bacteria, such as E. coli O157, which usually result in more severe illnesses.

Written by Grace Rattue