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Drinking Raw Milk: More Details on the Risks

In response to my recent blog, Drinking Raw Milk: It’s Not Worth the Risk, we received a number of questions. Here are some of the most frequently asked questions from our readers, along with my answers.

Why focus on raw milk? What about other foods that have made people sick?

A glass and carton of milkWe get a lot of questions from people who are trying to decide whether or not to drink raw milk, and we want to provide them with science-based information on the risks of drinking raw milk. 

I work with the group at the Centers for Disease Control and Prevention (CDC) that investigates outbreaks of foodborne illnesses caused by germs like Salmonella and E. coli O157:H7 (a dangerous form of E. coli). Over the years, we have collected extensive data based on experience investigating these outbreaks. Many different foods have been associated with recent outbreaks, such as unpasteurized juice and cider, eggs, and sprouts.

When determining if one food is riskier than another, it is important to understand how many people consume that food. For example, did you know that an estimated 4 percent of dairy products consumed in the United States are unpasteurized, based on a 2006-2007 FoodNet Population Survey, yet more than half of dairy-associated outbreaks are linked to raw milk products?

I know people who have been drinking raw milk for years, and it’s never made them sick. Why is that?

Several things can affect whether or not a person becomes sick after consuming a contaminated food or drink. These include the number and type of germs contaminating the food or drink, as well as the immune defenses of the person who consumes the food or drink.

The presence of germs in raw milk is unpredictable. The number of disease-causing germs in the raw milk may be too low to make a person sick at first, but the germs may later multiply so that there are enough to make the same person seriously ill. As seen in these videos, for some people, drinking contaminated raw milk just once could make them really sick; for others, illness comes after years of drinking raw milk.

I’ve heard that raw milk has enzymes that kill dangerous bacteria. Is that true?

No, the enzymes in raw milk are not strong enough to kill dangerous bacteria. In the United States, pasteurization is the only method routinely used to eliminate disease-causing organisms in milk.

My farmer has set up humane and sanitary conditions for raising his animals and producing raw milk. His animals are really healthy. Doesn’t this ensure that his milk is safe?

Even animals that appear healthy and clean may carry germs that can contaminate milk. Adhering to good hygienic practices during milking can reduce the risk of contaminating the milk, but it doesn’t eliminate it. If the milk is raw, small numbers of bacteria might multiply and grow in the milk before someone drinks it. No matter what precautions the farmer takes, it’s impossible to guarantee that raw milk is free of harmful germs.

What about raw milk that’s been laboratory tested for bacteria?

Negative tests do not guarantee that raw milk is safe to drink. People have become very sick from drinking raw milk that came from farms that regularly tested their milk for bacteria, and whose owners were sure that their milk was safe.

What are the statistics on outbreaks of illness related to raw milk?

Among dairy product-associated outbreaks reported to CDC between 1973 and 2009 in which the investigators reported whether the product was pasteurized or raw, 82% were due to raw milk or cheese. From 1998 through 2009, 93 outbreaks due to consumption of raw milk or raw milk products were reported to CDC. These resulted in 1,837 illnesses, 195 hospitalizations, and 2 deaths. Most of these illnesses were caused by Escherichia coli O157, Campylobacter, or Salmonella. It is important to note that a substantial proportion of the raw milk-associated disease burden falls on children; among the 93 raw dairy product outbreaks from 1998 to 2009, 79% involved at least one person less than 20 years old.

Reported outbreaks represent the tip of the iceberg. For every outbreak and every illness reported, many others occur, and most illnesses are not part of recognized outbreaks.

Keep in mind that reported outbreaks represent the tip of the iceberg. For every outbreak and every illness reported, many others occur, and most illnesses are not part of recognized outbreaks.

Can outbreaks be caused by pasteurized milk products?

Pasteurized milk and cheese products can cause outbreaks, but these are usually due to contamination that occurs after the pasteurization process. Also, the most common germ that affects pasteurized milk products is norovirus, which is typically spread from one person to another, not from animals to people. This is different from the germs that can most often contaminate raw milk like Salmonella and E. coli O157 H7, which are spread from animals to people. Also illness from norovirus typically lasts for only 2 days, whereas illness from Salmonella and E. coli is usually more serious.

For more statistics and other information, see Raw Milk Questions and Answers.

Updated on: November 18, 2011

TaggedRaw Milk