Health & Wellbeing

Raw milk can spread dangerous antibiotic-resistant genes, study finds

Raw milk can spread dangerous ...
Analyzing over 2,000 milk samples revealed unpasteurized milk carries antimicrobial-resistant genes than can quickly grow in volume when sitting at room temperature
Analyzing over 2,000 milk samples revealed unpasteurized milk carries antimicrobial-resistant genes than can quickly grow in volume when sitting at room temperature
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Analyzing over 2,000 milk samples revealed unpasteurized milk carries antimicrobial-resistant genes than can quickly grow in volume when sitting at room temperature
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Analyzing over 2,000 milk samples revealed unpasteurized milk carries antimicrobial-resistant genes than can quickly grow in volume when sitting at room temperature

A large study from food scientists at the University of California, Davis, has found unpasteurized milk, commonly known as raw milk, holds large volumes of antimicrobial-resistant genes which can very swiftly spawn dangerous bacteria when left at room temperature.

The researchers investigated 2,034 milk samples gathered from retail stores across five US states (California, Idaho, Arizona, South Carolina, and Maine). Four kinds of milk processing techniques were studied, from completely unpasteurized products, to vat pasteurized, high-temperature short time (HTST), and ultra-pasteurized (UHT) products.

The baseline results revealed the raw milk samples contained significantly higher levels of live bacteria compared to the other processed milks. However, those bacterial levels did remain stable as long as the milk was kept in a refrigerated state.

The researchers homed in on genetic material in the milk samples and discovered raw milk contained “dramatically more ARGs (antimicrobial-resistant genes) than pasteurized milk”. This is the second recent study to detect relevant levels of ARGs in raw milk samples. But more worrying was how rapidly bacteria with these genes appeared when raw milk was left at room temperature.

“Our study shows that with any temperature abuse in raw milk, whether intentional or not, it can grow these bacteria with antimicrobial resistance genes,” explains microbiologist Michele Jay-Russell, co-author on the new study. “It’s not just going to spoil. It’s really high risk if not handled correctly.”

The researchers express particular concern over the production of clabber, a traditional type of soured milk made by letting raw milk ferment at room temperature for several days. David Mills, co-author on the study, suggests those keen to create this fermented product should use a starter culture to inoculate milk. This, he says, will help people avoid culturing large volumes of antibiotic-resistant bacteria that may be present in raw milk.

“You could just be flooding your gastrointestinal tract with these genes,” say 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.”

Alongside these significant levels of ARGs in raw milk, the researchers profiled the broader bacterial populations present in the product. Lead author on the study Jinxin Liu says large volumes of “beneficial bacteria” were not found in the raw milk samples. This finding sits somewhat contrary to the common belief unpasteurized milk contains large volumes beneficial lactic acid bacteria which is subsequently destroyed in the pasteurization process.

“We don’t want to scare people, we want to educate them,” says Liu. “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.”

The new study was published in the journal Microbiome.

Source: UC Davis

8 comments
paul314
I wonder whether there's a correlation with subclinical doses of antibiotics fed to livestock.
piperTom
After 10,000 years of people consuming dairy milk, so glad finally to learn how dangerous it is.
Catweazle
Really... I was brought up on 'raw' milk, especially the Jersey variety, as were most of the cohort who, by their increased life expectation, are causing such a headache to the health services. It is my opinion that the immune system requires 'training' by being subjected to a variety of pathogens and there is a huge amount of trouble caused by the cleanliness fanatics with their myriad disinfectants and cleansing agents.
DavidIngram
Are we saying that the antimicrobial-resistant genes naturally occurring in nature, that man has consumed for thousands of years, is bad for us? Do we need to defeat nature again to make our artificial stuff work?
PWbest
Looks like the milk was "sampling was whole milk which is certified as organic and rBST free". Would be interesting to see this repeated with cows that were exclusively fed organic grasses.
Davida
Normally the "humans have been consuming raw dairy for tens of thousands of years (if not hundreds of thousands)" is dismissible as an appeal to nature. It is worth noting the threat that something we've been doing so long might poses to us; but if you don't want to drink unpasteurized milk, don't. I was lactose intolerant until adding raw dairy to my diet. Now I consume 3 gallons of raw dairy (yogurt and milk) per WEEK. I have purposely left raw milk out in the sun to culture before consuming. I will never return to pasteurized dairy products as long as I can source my raw product from a clean, respectable farm. I have no need to return to pasteurized milk.

"We don’t live in an antibiotic-free world anymore": what is that in regards to? The article says nothing about the anti-biotic resistant bacteria found in raw milk being pathogenic - they simply state that the anti-biotic resistant bacteria is there. Will someone more educated elaborate?
Eddy
Well, I can hear the screams now from the fancy cheese manufacturers that have campaigned long and hard to be able to use it in their products here in AUS, though I believe its use is commonplace in Europe.
ljaques
This study appears to be yet another hit piece on raw milk, though their only gripe is WARM milk. The title should have been WARM Raw Milk Bad! ;) How do these MRSA-like bugs thrive in other warm places, and why was that not addressed in the study? // Read the low numbers of problems from a 2011 report (from the "other side") via Ted Beals, MD: https://www.realmilk.com/safety/those-pathogens-what-you-should-know/ . Campy 34 our of 845k cases, Ecoli O157:h7 5 of 63k, Listeria 0 of 1591 in past 12 years. [Disclaimer: I'm not even a raw milk drinker.] QUESTION: Who is monitoring these "hall monitors"? Peers, get your game up.