A new study conducted by researchers from the University of California Davis explored the risks associated with raw milk, which is typically sold to consumers on the idea that it has better health properties than pasteurized milk.

According to the researchers, properly storing raw milk is crucial. When left out of the refrigerator, raw milk can develop antimicrobial-resistant genes. These genes don’t respond to traditional antibiotic treatment and could potentially develop into a superbug.  

“Two things surprised us,” said researcher Jinxin Liu. “We didn’t find large quantities of beneficial bacteria in the raw milk samples, and if you leave raw milk at room temperature, it creates dramatically antimicrobial-resistant genes than pasteurized milk.” 

“We don’t want to scare people, we want to educate them,” Liu continued. “If you want to keep drinking raw milk, keep it in your refrigerator to minimize the risk of it developing bacteria with antibiotic-resistant genes.” 

Eliminating the raw milk risk

To understand the risk that raw milk poses to consumers, the researchers analyzed over 2,000 raw milk samples. The samples hailed from five states and were all products that consumers could buy on store shelves. 

The researchers left the samples in a room-temperature environment and compared the results with more traditional-style milk that is pasteurized. Ultimately, when left outside the refrigerator, raw milk developed antibiotic-resistant bacteria much faster than pasteurized milk and in much higher quantities. 

The researchers say that bacteria are able to flourish in raw milk because of the subtraction of the pasteurization process, especially when not chilled properly. When raw milk curdles, it creates a yogurt-like substance known as clabber. Ingesting raw milk at warmer temperatures is particularly dangerous because antibiotic-resistant bacteria can multiply over time.

“You could just be flooding your gastrointestinal tract with these genes,” said researcher David Mills. “We don’t live in an antibiotic-free world anymore. These genes are everywhere, and we need to do everything we can to stop that flow into our bodies.” 

“Our study shows that with any temperature abuse in raw milk, whether intentional or not, it can grow these bacteria with antimicrobial resistant genes,” said researcher Michele Jay-Russell. “It’s not just going to spoil. It’s really high risk if not handled correctly.”