French chemist Louis Pasteur developed a method for preserving food using heat in 1864. The practice of thermal processing can be traced further back to 1117 in China where wine was heated to prevent it from souring. Pasteur utilized a similar principle for preserving wine and beer. His method was considered less aggressive because it involved heating under 50 to 60 degrees Celsius to protect food quality. This process has since been called pasteurization and has become a standard process in milk production since the 1900s.
Humans have been regularly consuming milk from domesticated mammals since the First Agricultural Revolution. It has become part of food production and the regular diet of both ancient and modern societies. But this was raw milk. The scientific consensus built around the germ theory and cases of milk-borne illnesses has made milk pasteurization essential beginning in the 20th century. However, in more recent years, several individuals and groups have advocated for raw milk consumption due to its purported health benefits.
The Health Risks From Raw Milk Consumption: Why You Should Not Drink Unpasteurized Milk
Background and Status
Raw milk advocates champion a wide array of alleged advantages. These range from enhanced taste and better nutritional profile to enhanced immune system and protection from allergy and asthma. Researcher B. Sozańska noted that some evidence suggests that certain components of raw milk may positively influence immune function but also underscored the need for definitive proof via additional studies and through controlled studies involving humans.
The fact remains that the risks of consuming raw milk outweigh the purported benefits. Milk is an excellent medium for microbial growth due to its rich nutrient composition. It has lactose and amino acids that are essential for many microorganisms. It also has a high water content and a pH level that creates a favorable environment for supporting microbial proliferation. Milk also contains various growth factors that stimulate the growth of specific microorganisms.
The United States Centers for Disease Control and Prevention or CDC asserts that raw milk, when improperly handled, constitutes a substantial risk factor for foodborne illness, resulting in hospitalization rates nearly three times higher than those associated with any other source. Data from 1998 to 2008 show that there were 202 outbreaks in the U.S. linked to drinking raw milk. These incidents resulted in 2645 illnesses and 228 hospitalizations.
Regulators in different countries have controlled the production and sale of raw milk. Some oblige producers to label raw milk products. For example, in the United Kingdom, raw milk is required to carry a warning saying it has not been pasteurized and may contain harmful microorganisms that can cause illness. The same is true in the European Union. Both Health Canada and the Singapore Food Agency prohibit the sale of raw milk for human consumption.
Diseases and Incidents
Some of the common disease-causing microorganisms that have been found thriving in raw milk include Campylobacter, Cryptosporidium, Escherichia coli, Listeria, Brucella, and Salmonella. The CDC warns that several groups, which include children under 5, adults aged 65 and above, pregnant women, and individuals with compromised immune systems are at a higher risk of serious illness from consuming raw milk contaminated with these pathogens.
J. A. Lucey noted that about 10 percent of tuberculosis cases in the U.S. prior to the wide adoption of pasteurization in the 1900s were attributed to milk consumption. Raw milk was also associated with 25 percent of all disease outbreaks from food and water consumption in the U.S. before the Second World War. Hence, in his review article, he underscored the fact that pasteurization has decreased the percentage of milk-associated food-borne disease outbreaks.
Most cases of milk-borne illnesses are not life-threatening. Taking medications like antibiotics and over-the-counter drugs helps relieve symptoms. However, in several cases, raw milk consumption can pose a serious health risk. Some infections induce serious illnesses like Guillain-Barré Syndrome, a rapid-onset and immune system-induced muscle weakness, and Hemolytic-Uremic Syndrome, a group of blood disorders that result in acute kidney injury.
Bacterial infection is the leading cause of milk-borne illnesses. Other pathogens like viruses, fungi, and parasites can also cause illnesses. Contaminated raw milk is an efficient vehicle of disease transmission because it can contaminate an entire dairy farm, result in cross-contamination in milk processing plants, post-pasteurization contamination, and spillover to other species. Spillover events to other species due to raw milk consumption have been documented.
Rundown of Potential Diseases From Raw Milk Consumption: Common Milk-Borne Illnesses
Remember that there are different diseases that can potentially arise from consuming raw milk depending on the type of pathogen, the amount of ingested pathogen, the time of pathogen incubation, and individual susceptibility. The following is a rundown of potential diseases or illnesses from raw milk consumption:
• Brucellosis: A common illness borne from raw milk consumption. This is caused by the Brucella bacteria. Symptoms include fever, muscle and joint pains, and headaches. It can further result in complications like endocarditis or inflammation of the inner layer of the heart and nervous system infections like meningitis and encephalitis.
• Gastroenteritis: This is an inflammation of the gastrointestinal tract that is caused by pathogens like Campylobacter, Escherichia coli, Listeria, and Salmonella. Symptoms include diarrhea and bloody diarrhea, abdominal cramps, vomiting, fever, and lack of energy. Dehydration may also occur when left unmanaged.
• Query Fever: This is an infection caused by Coxiella burnetii. The bacterium primarily spreads through inhalation of contaminated dust or aerosols from infected animals but can also be transmitted by consuming raw milk. Most people develop no symptoms or mild illness. Some can develop high fever, headaches, and muscle pain.
• Scarlet Fever: Raw milk can carry the Streptococcus pyogenes bacteria. Its consumption increases the risk of developing scarlet fever. This is true for vulnerable groups. Symptoms include sore throat, fever, headache, swollen lymph nodes in the neck, and a distinctive rash on the tongue called white or red strawberry tongue.
• Tuberculosis: Milk was one of the main routes of transmission of tuberculosis. This illness is caused by Mycobacterium. The particular milk-induced tuberculosis is caused by the specific Mycobacterium bovis species. This microorganism is the causative agent of tuberculosis in cattle and can cause zoonotic tuberculosis in humans.
Note that listeriosis or infection from Listeria is particularly dangerous for pregnant women, newborns, elderly individuals, and those with weakened immune systems. It can cause miscarriage, stillbirth, meningitis, and severe bloodstream infections. Severe cases of salmonellosis from Salmonella can lead to bloodstream infections and require hospitalization. E. coli infection can lead to Hemolytic-Uremic Syndrome that can cause kidney failure in children.
It is important to underscore the fact that there are population groups that are vulnerable to severe cases of milk-borne illnesses. These include infants and young children, pregnant women, older adults, and those with weakened immune systems like cancer patients, transplant recipients, and individuals with chronic illnesses. Pasteurization ensures safer milk consumption. However, even pasteurized milk can become contaminated if not handled or stored properly.
Raw milk consumption can also contribute to the development and spread of antibiotic-resistant bacteria or superbugs. It can harbor antibiotic-resistant bacteria that originate from infected cows treated with antibiotics or from environmental contamination during milking. Bacteria in raw milk can transfer resistance genes to other bacteria in the human gut through horizontal gene transfer. This can enhance the proliferation of antibiotic-resistant bacteria in the body.
Consumption of raw milk containing resistant bacteria can lead to infections that are difficult to treat. Furthermore, the introduction of antibiotic-resistant bacteria from raw milk can alter the balance of the gut microbiome, potentially promoting the persistence of resistant strains in the gastrointestinal system. Pathogens shed from infected individuals into the environment can further spread antibiotic resistance. Pasteurization lessens risks from these resistant bacteria.
FURTHER READINGS AND REFERENCES
- Hassani, S., Moosavy, M.-H., Gharajalar, S. N., Khatibi, S. A., Hajibemani, A., and Barabadi, Z. 2022. “High Prevalence of Antibiotic Resistance in Pathogenic Foodborne Bacteria Isolated From Bovine Milk. Scientific Reports. 12(1). Springer Science and Business Media LLC. DOI: 1038/s41598-022-07845-6
- Langer, A. J., Ayers, T., Grass, J., Lynch, M., Angulo, F. J., and Mahon, B. E. 2012. “Nonpasteurized Dairy Products, Disease Outbreaks, and State Laws—United States, 1993–2006.” Emerging Infectious Diseases. 18(3): 385-391. Centers for Disease Control and Prevention. DOI: 3201/eid1803.111370
- Lucey, J. A. 2015. “Raw Milk Consumption.” Nutrition Today. 50(4): 189-193. Ovid Technologies (Wolters Kluwer Health). DOI: 1097/nt.0000000000000108
- Sozańska, B. 2019. “Raw Cow’s Milk and Its Protective Effect on Allergies and Asthma.” Nutrients. 11(2): 469. MDPI AG. DOI: 3390/nu11020469
- United States Food and Drug Administration. 2024. “The Dangers of Raw Milk: Unpasteurized Milk Can Pose a Serious Health Risk.” Food. United States Food and Drug Administration. Available online