Scientific evidence raises concerns over foodborne pathogens in unpasteurized milk, while many claims about its nutritional and digestive benefits remain unproven.
Raw milk is increasingly promoted by wellness advocates as a more natural alternative to pasteurized milk, with claims that it offers superior nutrition, supports gut health and may reduce the risk of allergies. However, a scientific review published on October 1, 2026, by Nicola Holden, Ph.D., and Gil Domingue, Ph.D., highlights the established microbiological risks associated with unpasteurized milk and the limited evidence supporting many of its purported health benefits.
The review, Raw Milk Under the Microscope: Separating Safety Risks From Nutritional Claims, examines the differences between raw and pasteurized milk, foodborne disease outbreaks, regulatory approaches and ongoing research into potential health effects. Its central finding is that pasteurization significantly reduces exposure to harmful microorganisms, while current evidence does not establish that raw milk provides superior overall nutrition, meaningful probiotic benefits or improved lactose digestion.
The findings come amid growing consumer interest in minimally processed foods and renewed debate over whether traditional dairy products offer health advantages that conventional processing may diminish.
Raw milk is milk that has not undergone pasteurization or an equivalent treatment designed to reduce harmful microorganisms. It may come from cows, goats, sheep or buffaloes.
Pasteurization uses controlled heat treatment to inactivate disease-causing microorganisms while retaining the milk’s overall nutritional value. One commonly used method, high-temperature, short-time (HTST) pasteurization, heats milk to at least 72°C (161°F) for 15 seconds, although requirements vary by processing method.
Ultra-high-temperature (UHT) processing uses higher temperatures, approximately 138°C (280°F) for a fraction of a second, to inactivate vegetative microorganisms and most bacterial spores.
According to the review, commercial pasteurization, combined with improved farm hygiene, substantially reduces the risks associated with pathogens including:
These pathogens can enter milk through infected animals, contaminated farm environments, milking equipment or inadequate handling practices. Importantly, animals carrying harmful microorganisms may not display visible signs of illness.
The review highlights epidemiological evidence linking access to unpasteurized dairy products with increased foodborne illness outbreaks.
In the United States, 79% of dairy-associated foodborne illness outbreaks reported between 1998 and 2011 were linked to raw milk and raw cheese products.
A separate analysis covering 2013–2018 found that jurisdictions where unpasteurized milk was accessible experienced 3.2 times as many outbreaks as jurisdictions where retail sales were prohibited. The reported consequences included 98 hospitalizations, ten cases of haemolytic uraemic syndrome (HUS), two cases of Guillain-Barré syndrome or Miller Fisher syndrome, and two deaths.
Evidence from other regions also demonstrates the potential consequences:
These figures illustrate the potential public health consequences of consuming unpasteurized dairy products. They should, however, be interpreted within the time periods and populations covered by the respective studies rather than as estimates of the risk from every individual serving of raw milk.
Raw milk can carry several types of microorganisms capable of causing serious illness. Contamination may occur at multiple points between the farm and the consumer.
1. STEC
Shiga toxin-producing E. coli can be carried by ruminants and shed into the environment through manure. Contamination may spread to milk through farm environments and inadequate hygiene. Certain STEC infections can cause HUS, a potentially life-threatening complication affecting the kidneys.
2. Salmonella
Salmonella can cause fever, diarrhoea and abdominal cramps. The bacteria may enter the food chain through contaminated animals, equipment or handling environments.
3. Campylobacter
This pathogen is associated with gastrointestinal illness and has been a leading cause of outbreaks linked to raw milk in several European investigations.
4. Listeria monocytogenes
Listeria is particularly concerning because it can grow at refrigeration temperatures. Severe infections are more likely among pregnant women, older adults and people with weakened immune systems.
5. Other biological hazards
The review also identifies Brucella species, Mycobacterium bovis, Cryptosporidium and Toxoplasma gondii among relevant dairy-associated hazards. Research involving raw milk produced in some low- and middle-income countries has additionally identified concerns involving toxins, antibiotic residues and heavy metals.
Filtering milk may remove visible particles, but it cannot be relied upon to eliminate pathogenic microorganisms. Likewise, refrigeration does not make contaminated raw milk safe.
One of the most common arguments in favour of raw milk is that heat treatment destroys important nutrients. However, the review concludes that there is no meaningful difference in overall macronutrient value between raw and pasteurized milk.
Pasteurization can affect some heat-sensitive vitamins, including vitamin C, but milk is naturally a relatively limited source of this vitamin. A meta-analysis discussed in the review found that pasteurization had minimal overall effects on milk’s nutritional value. Vitamin B2 was identified as an area requiring further investigation.
Claims that raw milk contains enzymes that substantially improve digestion are also not supported by convincing evidence. Human digestion relies primarily on enzymes produced by the pancreas and intestine, and many enzymes present in milk either survive pasteurization or are broken down in the stomach before they can make a meaningful contribution to digestion.
Similarly, raw milk does not naturally contain enough lactase to reliably alleviate lactose intolerance.
The evidence therefore does not support treating raw milk as nutritionally superior simply because it has not been heat-treated.
Another frequently promoted benefit is that raw milk contains beneficial bacteria that support the gut microbiome.
However, the review notes that the microbial population of raw milk is highly variable. It may contain microorganisms with potentially beneficial properties, but it can also harbour disease-causing bacteria. The levels of potentially probiotic microorganisms generally have not been shown to provide an established gut health benefit.
This differs from commercial probiotic foods, which may contain selected microbial strains at specified concentrations with demonstrated benefits.
The presence of certain gut-associated bacteria in raw milk can also indicate faecal contamination rather than a health advantage.
Consequently, the assumption that consuming a more diverse population of live microorganisms automatically improves gut health is not scientifically justified. The identity, concentration, safety and demonstrated function of microorganisms all matter when evaluating probiotic claims.
The relationship between raw milk and allergies is more complex than claims about nutrition or digestion.
Observational studies have associated raw milk consumption during childhood with lower rates of certain allergic and respiratory conditions, including asthma, hay fever and allergic sensitisation. Some research has also reported an association between early-life raw milk consumption and approximately 30% lower risk of respiratory tract infections compared with UHT milk.
However, these findings do not establish that raw milk itself causes the observed effects.
Many studies involve children growing up on farms, where exposure to animals, environmental microorganisms and other factors may influence immune development. Researchers therefore face difficulties distinguishing the effects of raw milk consumption from the broader environmental influences sometimes described as the “farm effect.”
Potential mechanisms under investigation include omega-3 polyunsaturated fatty acids and microRNAs, which may influence inflammatory and immune responses.
Although these findings provide avenues for further research, they do not establish raw milk as a safe or effective way to prevent allergies. The observed associations must also be considered alongside the documented risk of foodborne infection.
The risks associated with unpasteurized milk are not limited to beverages. Cheese made from raw milk has also been implicated in serious foodborne disease outbreaks.
The review describes a multistate US STEC O157 outbreak in 2026 in which epidemiological evidence implicated cheese made from unpasteurized milk. Although the producer voluntarily withdrew the implicated product, the outbreak strain was not recovered from the tested cheese.
A similar challenge occurred during the 2016 Scottish STEC O157 outbreak associated with raw milk cheese. Investigations implicated a particular cheese, and the outbreak resulted in one death, even though the outbreak strain was not detected in tested samples of the implicated product.
These cases demonstrate a key limitation in foodborne disease investigations: failure to detect a pathogen in the samples tested does not automatically exclude a food as the source of an outbreak. Contamination may be unevenly distributed, and the implicated product may no longer be available by the time testing takes place.
The review highlights the importance of combining epidemiological evidence, appropriate sampling and molecular techniques such as whole genome sequencing to investigate contamination and trace pathogens.
Rules governing raw milk vary considerably across countries and jurisdictions.
In the United States, some states permit retail sales, while others restrict sales to farms or direct-to-consumer channels. Federal law prohibits interstate sales of raw milk for direct human consumption.
In the United Kingdom, the sale of raw milk for direct human consumption is permitted under specified conditions in England, Wales and Northern Ireland, while it is prohibited in Scotland. Across the European Union, requirements and permitted sales arrangements vary under applicable national and regional rules.
The review also describes changes in consumer demand. In the United Kingdom, raw milk sales reportedly increased fivefold over five years, alongside wider interest in unprocessed foods.
Regulatory decisions must account for consumer choice, production practices, food business responsibilities and the potential costs of foodborne disease. These costs extend beyond medical treatment to outbreak investigations, public health interventions and lost productivity.
The authors highlight the need for effective inspections, supply-chain oversight, testing and hygiene controls to reduce risks wherever raw milk is legally produced or sold.
Researchers are exploring whether alternative processing technologies could reduce microbial hazards while preserving milk components that may have biological value.
The objective is to determine whether milk can be made microbiologically safe without unnecessarily affecting components being investigated for potential health benefits.
However, these approaches remain an area of research. Any alternative would need to demonstrate reliable pathogen control and substantiate its claimed nutritional or biological advantages before being considered an established substitute for conventional pasteurization.
Until such evidence is available, the review identifies pasteurization as an important established measure for reducing the microbiological risks associated with milk consumption.
The evidence reviewed by Holden and Domingue points to several practical considerations for consumers:
Raw milk remains at the centre of a debate involving traditional food practices, consumer preferences, nutritional claims and public health. Although observational research has identified associations between childhood raw milk consumption and lower rates of some allergic and respiratory conditions, these findings do not establish causation or outweigh the need to consider established microbiological hazards.
The available evidence does not demonstrate that raw milk offers superior overall nutrition, meaningful probiotic benefits or reliable relief from lactose intolerance compared with pasteurized milk. By contrast, the ability of pasteurization to reduce exposure to major foodborne pathogens is well established.
For consumers, producers and regulators, the challenge is to distinguish emerging scientific questions from established evidence. Future research may help identify ways to preserve potentially beneficial milk components while controlling pathogens, but any proposed health advantage must be supported by rigorous evidence of both safety and efficacy.
Source: Nicola Holden, Ph.D., and Gil Domingue, Ph.D., Raw Milk Under the Microscope: Separating Safety Risks From Nutritional Claims, October 1, 2026.