What Is Raw Milk And Why Is It Harmful?

Milk is a highly nutritious food, and an important source of amino acids and minerals such as phosphorus and calcium, which contributes to bone health.

Cow picture from Shutterstock

Historically, milk was prone to contamination by bacteria from cows that could cause severe illness in humans. This remains the case with raw (unpasteurised) milk. The tragic death of a Victorian toddler this week is a stark reminder of these risks.

Pasteurisation involves heating the product to 72°C for 15 seconds. The method was originally employed to destroy bacteria in wine and beer that caused these products to spoil. It was quickly realised that this process could also be applied to milk to destroy harmful bacteria, and make milk safer for human consumption.

Pasteurisation was first introduced in Australia in the late 1950s and remains a legal requirement for milk produced for human consumption in Australia.

Nowadays, some of the important bacteria that pasteurisation targeted, such as those that cause tuberculosis, are no longer as problematic. So why do we continue to pasteurise milk?

The animals we use for milking can sometimes carry other pathogenic organisms that are capable of causing disease in humans. They can be found on hides or shed in the faeces.

Even healthy animals may be a source of organisms that are harmful to people. Such pathogens may be present in the farm environment, including soil, water, on pasture and in animal feeds. These pathogens can enter the milk during milking and if such milk is consumed, it can cause disease.

The most common pathogens found in association with dairy farms and milking animals include bacteria such as Escherichia coli (E. coli), Campylobacter and Salmonella, but other pathogens such as parasites like Cryptosporidium, a type of gastro, may also be present.

Campylobacter and Salmonella can cause severe diarrhoea and certain types of E. coli, particularly those known as Shiga toxin-producing E. coli (STEC), can cause very severe disease which impairs kidney function and may result in death.

Milk is highly nutritious to bacteria. Bacteria can quickly proliferate if their growth is not inhibited. Stopping the growth of bacteria in milk requires either heating to kill the bacteria, or chilling, which will not kill the bacteria but will slow down their growth.

E. coli, for instance, can go from ten cells to 100 million cells in just over six hours at 30°C. Only ten cells may be required to make someone ill. If such an organism is likely to be present, it's important that any potential growth is stopped.

These harmful bacteria have caused outbreaks and disease associated with the consumption of raw milk in many countries. Data from the United States indicates that over a 13 year period to 2011, there were 2,384 illnesses, 284 hospitalisations and two deaths associated with the consumption of raw milk.

In Australia, raw milk contaminated by bacteria such as Campylobacter and Salmonella caused at least nine outbreaks of disease between 1997 and 2008, leading to 117 cases of illness.

So why do people choose to drink raw milk?

Advocates of raw milk often claim improved health benefit and nutritional value, or desiring a product which has not undergone further processing, retaining bacteria naturally present in milk.

But there is no evidence that the health benefits of milk are compromised by pasteurisation.

The defining difference between pasteurised and raw milk is the bacteria that are present. As soon as milk is secreted from the udder, it is at risk of contamination by many different bacteria as it makes its journey to our table. This includes harmful bacteria. These bacteria can lead to severe illness in humans, particularly children and the elderly.

For these reasons, raw milk continues to have a far higher risk of causing illness. Pasteurisation remains an important step in ensuring we can continue to enjoy safer, nutritious milk.

The Conversation

Edward Fox is a Food Safety and Microbiology Research Scientist at CSIRO. Narelle Fegan is a Food Microbiologist at CSIRO.

This article was originally published on The Conversation. Read the original article.


Comments

    The people drinking this should go back to drinking soy milk, if your dumb enough to drink it you deserve to get sick.

      Unfortunately some give it to their kids, who are not in a position to think critically, with tragic results: http://www.abc.net.au/news/2014-12-11/raw-milk-no-evidence-of-health-benefit-nutritionist-body-says/5960588

    Unfortunately, like many medical myths, some in the public will continue to believe pasteurisation is harmful to milk and that unpasteurised milk is better...

    I mean, even the milk in question involved in the recent deaths were clearly labelled "not for human consumption"...So the people who drank this stuff are not oblivious to the dangers. They chose not to believe in them, resulting in fatal consequences.

    I say the parents should be brought up on child abuse and negligent homicide charges to be honest.

      Unpasteurised milk isn't necessarily harmful or in any way dangerous, provided it is consumed quickly.

      Unless you got the milk out of the cow yourself that very morning, it is safe to say that it is unsafe to drink. That is where most of these raw milk = good nutters go wrong.

      The supplier of the milk claims she drinks it all the time, but they still label it as bath milk and for cosmetic purposes only.

      I agree its definitely negligence, it should be treated just like feeding anything that is labeled as for consumption to a kid, say radiator fluid.

      Its weird enough that we drink cows milk anyway since it wasn't designed for us *(don't get me wrong i love it, wouldn't touch goats/etc milk) , i wouldn't go up and suck a cows teat i sure as hell wont drink raw cows milk.

        The not fit for human consumption/bath milk label is used to get around that law. I remember watching a short documentary on it once but cannot find it now. I did find this story on Raw Camel milk here in Perth. Using the same label. Seems to be quite beneficial. I don't know if I could trust it though.
        edit - Helps if I include the link... http://www.dailytelegraph.com.au/news/nsw/sunday-night-reporter-pj-madam-drinks-camel-milk-for-a-month-to-test-its-health-benefits/story-fni0cx12-1227115069267

        Last edited 15/12/14 11:33 pm

    Another death and more suffering caused by the "natural is better" crowd.

    I don't support drinking unpasteurised milk - I don't drink it, and I wouldn't feed it to my kids.

    But people should realise that although the risks are there, they're very low: my parents were dairy farmers, and my whole family grew up drinking unpasteurised milk without any problems at all.

      If you are drinking it immediately, you're probably right.

      But milking, storing, transporting, storing, purchasing, storing then consuming dramatically increases the risks. Risks which are entirely unnecessary.

    @rybo bacteria in unpasteurised milk requires time to become a health problem. As @dre_ said, drinking it quickly after it comes from the cow is fine as bacteria don't have time to multiply sufficiently - it's when it is bottled and sent to market that bacteria have the time to grow and become an issue. It's especially dangerous for toddlers or people already sick from other conditions.

    http://home.iprimus.com.au/foo7/badfood.html

    http://www.foodauthority.nsw.gov.au/_Documents/science/Food_Safety_Scheme_Risk_Assessment.pdf

    A couple of interesting articles relating to incidences of food poisoning. The second article is dated from 2009, however if everyone reacted to some of these numbers in the way people are currently reacting to the raw milk story we would all be starving right now.

      Not really. Campy, Listeria, Salmonella and Norovirus (as per first link) are all usually self-limiting and don't require anything other than some fluids. E. Coli O157:H7 can cause permanent kidney failure on the other hand (which is the concern of unpasteurised milk). The issue here is that people drink unpasteurised milk for entirely no benefit and at risk of significant injury, no matter how small the initial risk is. It's a bit like everyone choosing not to have polio injections because the risk of getting polio these days is very small - it would be an incredibly foolhardy thing to do.

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