More than half of U.S. states allow the sale of raw milk directly from farms to consumers, including Delaware. The state legislature passed a law in May to allow the sale of unprocessed, unpasteurized milk from dairy producers who hold a permit.  

Some have celebrated the legalization of raw milk around the country, claiming it tastes better and has some nutritional benefits. And President-elect Donald Trump’s pick to lead the Department of Health and Human Services (DHHS), Robert F. Kennedy Jr., says he wants to make raw milk more accessible.

Meanwhile, the U.S. Food and Drug Administration, one of the DHHS agencies Kennedy will lead, cautions against drinking raw milk and since the 1980s has banned it from being sold across state lines.  

Raw milk comes directly from cows, sheep or goats. Some health and food safety experts say drinking raw milk doesn’t come without health risks. Lately, those concerns have been elevated as a deadly strain of bird flu is infecting dairy farms around the country.

Kali Kniel is a professor of microbial food safety at the University of Delaware who studies the pathogens that may be present in raw milk and ways to communicate food safety to the public. 

Q: Milk and other dairy products that sit on shelves at the grocery store are pasteurized. What does this process involve and why is it important for dairy products?  

Kniel: Pasteurization of milk is a process of heating milk and passing it between heated stainless steel plates until it reaches 161 degrees Fahrenheit. It is held at that temperature for around 15 seconds before it is quickly cooled to 39 degrees Fahrenheit. This process is intended to kill the pathogenic bacteria that could make a person sick. 

Q: How does this process affect milk’s quality and nutritional value?

Kniel: Scientific studies have shown that pasteurization does not significantly change the nutritional value of milk. Unpasteurized milk may have more vitamin C, which does not survive the pasteurization process, but milk is not considered a good source of vitamin C, as it contains less than 10% of the Recommended Dietary Allowance (RDA), the average amount of nutrients it takes to meet a healthy person’s needs.

There are no beneficial bacteria in raw milk. Milk (pasteurized or raw) is not a good source of probiotic or potentially beneficial bacteria, so for that consumers should choose yogurt and other fermented dairy products as well as other fermented products. 

Scientific studies using animal models have shown no difference in how calcium in raw milk and pasteurized milk is absorbed by the human body.

Q: Popularity in drinking raw milk is increasing, despite the U.S. Food and Drug Administration advising that it’s not safe to drink. What are the health risks that come with drinking raw milk?

Kniel: Raw milk may contain pathogenic bacteria, including Campylobacter, Salmonella, pathogenic types of E. coli, Listeria and Brucella, as well as the protozoan parasite Cryptosporidium. These are all zoonotic microbes, which means they can be transmitted from animals to humans. Often the animal does not appear ill, so it is not possible to determine if an ill animal is shedding these pathogens in its feces that can contaminate milk. 

Microbial testing of the finished product and environmental monitoring programs may be helpful, but do not guarantee that the raw milk is absent of these pathogens. Milk can be contaminated with these pathogens from direct contamination with feces or from environmental conditions. Cross-contamination from dairy workers can also happen, even when people are trying their best to reduce the risk of cross-contamination. 

The likelihood of a disease outbreak occurring associated with a person consuming raw milk is relatively high given that others may also be exposed. Unpasteurized milk will have a relatively short shelf life and may not be available for testing. Following good hygiene practices on the farm and during milking such as biosecurity around the farm, appropriately sanitizing equipment and monitoring the health of animals can reduce the chance of milk contamination, but not eliminate it.

There have been numerous outbreaks of illness associated with raw milk as well as cheese made from raw milk. Persons most at risk of illness associated with drinking raw milk include children, in particular 5 years of age and under, individuals aged 65 and over, pregnant women and immunocompromised individuals. It should be noted that all outbreaks of illness associated with raw milk have included individuals under 19 years of age. Children may be most vulnerable, as they cannot voice an opinion on consumption and risk of raw milk if it is in their household. 

The Center for Disease Control and Prevention (CDC) collects data on foodborne disease outbreaks voluntarily reported by state, local or territorial health departments. According to the CDC from 2013 to 2018 there were 75 outbreaks of illness linked to raw milk consumption. These outbreaks include 675 illnesses and 98 hospitalizations. Most of these illnesses were caused by Campylobacter, shiga-toxigenic E. coli, or Salmonella. 

An increase in outbreaks has been correlated with changes in the availability of raw milk. For example, between 2009 and 2023, there were 25 documented outbreaks in the state of Utah, which has 16 raw milk retailers licensed by the Utah Department of Agriculture and Food. In all of these outbreaks, the raw milk was contaminated with the bacteria Campylobacter, which typically causes gastroenteritis symptoms like diarrhea and nausea, but may also cause chronic illness, including Guillain-Barré syndrome which can cause paralysis.

Q: How likely are these illnesses to happen from drinking raw milk?

Kniel: It is difficult to say. Foodborne illness is often underreported, depending on how severe people’s symptoms are. 

According to one study, only about 3.2% of the U.S. population drinks raw milk, while about 1.6% eats cheese made from raw milk. But compared with consumers of pasteurized dairy products, they are 840 times more likely to experience an illness and 45 times more likely to be hospitalized. The authors of this work used the CDC’s national reporting system to analyze data from 2009 to 2014.

Q: Despite health risks, why do some people still drink raw milk?

Kniel: Some people feel a nostalgic connection to raw milk, and others may feel that foods that are not treated with heat retain certain nutrients and enzymatic activity. I am not aware of any peer-reviewed rigorous scientific studies that indicate the nutritional benefits of consuming raw milk over time, given the risks of potential for illness, combined with a well balanced diet full of healthful food choices. 

It remains that raw milk is particularly risky for children to consume, as children can get sick from consuming fewer bacterial cells compared to adults.

Q: More than 900 cases of highly pathogenic avian influenza — the disease commonly known as bird flu — have been detected in dairy cattle across 16 states, and at least 40 people have been infected with the disease from close contact with dairy cows. Raw milk is being tested for the virus. With raw milk gaining interest among consumers, what are the possible consequences? Does it elevate the risk of bird flu spreading further to people?

Kniel: There remain clear risks of transmission of pathogenic bacteria through consumption of raw milk, and now with the potential for contamination of raw milk with avian influenza, it is even more important that consumers protect themselves by drinking pasteurized milk. 

The people most at risk right now are those involved with the milking process and in the handling of dairy cattle. So it is important that those individuals be aware of the risks and take appropriate precautions, including hand washing and wearing appropriate personal protective equipment like protective clothing, gloves, face shields and eye protection. 

Q: As of December, the U.S. Department of Agriculture is requiring 13 states to share raw milk samples so the agency can test for bird flu viruses. How could this testing better help us understand the virus? 

Kniel: I think it is very smart that USDA is leading the National Milk Testing Strategy, which will help us understand the extent of infected herds. Surveillance of microorganisms is an important way to assess risk so we can develop appropriate strategies to reduce and control these risks.