Unpasteurized milk, commonly called raw milk, is milk that has not been heated to kill bacteria and other microorganisms. Pasteurization typically involves holding milk at around 72°C (161°F) for 15 seconds, a process that eliminates most pathogens. Skipping that step leaves the milk’s microbial community intact, including both beneficial bacteria and potentially dangerous ones. Whether that trade-off makes raw milk worth drinking depends on what you value and how much risk you’re willing to accept, but the epidemiological evidence tilts heavily toward caution.
What Lives in Raw Milk
Raw milk is not a sterile product with a few stray germs in it. It is a complex microbial ecosystem. Studies using genetic sequencing have identified hundreds of bacterial genera in a single set of cow’s milk samples. The dominant groups at the broadest level are Firmicutes and Proteobacteria, which together typically account for roughly 70 to 80 percent of the bacterial community, with Actinobacteria and Bacteroidetes making up much of the remainder.1Scientific Reports. Variation in Raw Milk Microbiota Throughout 12 Months and the Impact of Weather Conditions At the genus level, Pseudomonas, Acinetobacter, Streptococcus, and Lactobacillus are among the most frequently detected.2PubMed Central. Microbial Properties of Raw Milk throughout the Year and Their Relationships to Quality Parameters
Many of these bacteria are harmless or even useful in cheesemaking. Lactic acid bacteria like Lactococcus, Lactobacillus, and Leuconostoc are the workhorses behind traditional fermented dairy products, and they occur naturally in raw milk at varying levels.3FEMS Microbiology Reviews. The complex microbiota of raw milk But Pseudomonas and other psychrotrophs, bacteria that thrive in cold temperatures, also flourish during refrigerated storage. These are the organisms that make raw milk spoil faster than pasteurized milk, and their presence is a reminder that refrigeration alone does not freeze the microbial clock.
The Pathogens That Matter
The bacteria that cause illness in raw milk are not exotic rarities. They are well-known foodborne pathogens: Campylobacter, Salmonella, E. coli O157:H7, and Listeria monocytogenes. Campylobacter is the single biggest offender. In a U.S. analysis of outbreaks linked to unpasteurized milk from 2013 to 2018, Campylobacter caused more outbreaks and more illnesses than any other pathogen, accounting for roughly half of all cases.4PubMed Central. Foodborne illness outbreaks linked to unpasteurised milk and relationship to changes in state laws – United States, 1998–2018 Studies of raw milk samples have found Campylobacter jejuni in 20 percent of tested raw milk in some surveys.5PubMed Central. Prevalence of Campylobacter jejuni and Campylobacter coli in raw milk and some dairy products
A Belgian survey of raw milk sold directly from farms found E. coli O157 in about 0.7 percent of samples and Listeria monocytogenes in roughly 6 percent.6Journal of Food Safety. A Belgian Survey of Hygiene Indicator Bacteria and Pathogenic Bacteria in Raw Milk and Direct Marketing of Raw Milk Farm Products Those percentages sound small, but the consequences of infection with either organism can be severe. Listeria is particularly dangerous for pregnant women, older adults, and anyone with a compromised immune system. E. coli O157:H7 can trigger hemolytic uremic syndrome (HUS), a kidney-damaging complication that disproportionately strikes young children.
The sheer scale of the risk difference between raw and pasteurized dairy is striking. A study estimating outbreak-related illness rates from 2009 to 2014 in the United States found that unpasteurized dairy products caused roughly 840 times more illnesses and about 45 times more hospitalizations per unit consumed than pasteurized products.7Emerging Infectious Diseases. Outbreak-Related Disease Burden Associated with Consumption of Unpasteurized Cow’s Milk and Cheese, United States, 2009–2014 Those numbers reflect how effectively pasteurization removes pathogenic organisms, and how much risk remains when it’s skipped.
Who Faces the Greatest Danger
Not everyone who drinks contaminated raw milk will end up in the hospital. Many Campylobacter infections cause a few days of diarrhea and resolve on their own. But the consequences can be far worse for vulnerable groups. During the 2013–2018 outbreak period in the United States, about 14 percent of the people sickened by unpasteurized milk were children under five, and another 34 percent were between five and nineteen.4PubMed Central. Foodborne illness outbreaks linked to unpasteurised milk and relationship to changes in state laws – United States, 1998–2018 Children made up a disproportionate share of severe outcomes. Ten cases of HUS and two cases of Guillain-Barré syndrome or its variant were reported during the same period, along with two deaths.
A Canadian case report describing a pediatric HUS case linked to E. coli O157:H7 from raw milk consumption underscored that the health risks to children can far outweigh any potential benefits.8PubMed Central. Public health risks of raw milk consumption: Lessons from a case of paediatric hemolytic uremic syndrome HUS can cause permanent kidney damage, and in rare cases it is fatal. For families considering raw milk for children, this is the risk that public health agencies most urgently want on the table.
Does Raw Milk Have More Nutrients
One of the most common arguments for drinking raw milk is that pasteurization destroys vitamins. There is a kernel of truth here, but the practical significance is thin. A systematic review and meta-analysis examining the effects of pasteurization on milk vitamins found that concentrations of vitamins B1, B2, C, and folate did decrease after heat treatment. Vitamins B12 and E also declined, while vitamin A actually increased.9PubMed. A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes The review’s authors noted, however, that the overall nutritive impact was minimal because many of these vitamins are present in relatively low levels in milk to begin with. Vitamin B2 (riboflavin) is the notable exception: milk is a significant dietary source of B2, and the small reduction from pasteurization could matter for people whose B2 intake is already marginal.
Beyond vitamins, pasteurization also denatures some of the minor whey proteins in milk. At standard high-temperature short-time pasteurization conditions (72°C for 15 seconds), about 59 percent of lactoferrin and 12 percent of immunoglobulin G (IgG) were denatured in one study, while bovine serum albumin was least affected.10PubMed. Denaturation of selected bioactive whey proteins during pasteurization and their ability to modulate milk immunogenicity Lactoferrin has antimicrobial properties, and IgG is part of the immune system. Raw milk advocates point to these proteins as evidence that raw milk supports immune health. The issue is that we don’t have good clinical evidence showing these proteins, consumed orally and digested in the stomach, deliver meaningful immune benefits to adults. They are biologically interesting, but the leap from “present in raw milk” to “improves your health when you drink it” has not been made convincingly in controlled trials.
The Allergy and Asthma Connection
The most scientifically interesting argument for raw milk involves allergies and asthma. Multiple epidemiological studies, particularly of children growing up on farms in Europe, have found that early-life consumption of raw milk is associated with lower rates of asthma, hay fever, and allergic sensitization. The GABRIELA study, one of the largest, found that children who consumed raw milk had roughly 40 percent lower odds of asthma and about half the odds of hay fever compared with those who didn’t, even after adjusting for other farm exposures. Boiled farm milk did not show the same protective effect.11PubMed. The protective effect of farm milk consumption on childhood asthma and atopy: the GABRIELA study
A meta-analysis pooling multiple studies confirmed these associations, finding reduced odds of asthma, current wheeze, hay fever, and allergic sensitization among children who consumed raw milk early in life.12PubMed. The Beneficial Effect of Farm Milk Consumption on Asthma, Allergies, and Infections: From Meta-Analysis of Evidence to Clinical Trial A broader review characterized the epidemiological evidence as showing raw milk to be one of the most effective protective factors against allergies in both farm and non-farm populations.13PubMed Central. Raw Cow’s Milk and Its Protective Effect on Allergies and Asthma
The catch is that these are observational studies. Children on farms differ from urban children in dozens of ways, and while researchers have tried to control for confounders, it is extremely difficult to isolate the effect of the milk itself from everything else about farm life — barn dust, animal exposure, a broader microbial environment. The heat-sensitive whey proteins in raw milk are plausible candidates for the protective effect, which is why boiled milk doesn’t seem to work the same way. But recommending raw milk for allergy prevention would mean exposing children to the very pathogens they’re most vulnerable to. Researchers are working on ways to preserve the beneficial components of raw milk while removing the pathogens, but that work is still in progress.
Raw Milk and Lactose Intolerance
A persistent claim among raw milk enthusiasts is that people with lactose intolerance can drink raw milk without symptoms, supposedly because it contains bacteria that help digest lactose. A randomized controlled trial directly tested this. Adults with confirmed lactose malabsorption drank raw milk and pasteurized milk on separate occasions, and researchers measured both hydrogen breath levels (a marker of undigested lactose) and self-reported symptoms. The result was clear: raw milk did not reduce lactose malabsorption or intolerance symptoms compared with pasteurized milk.14PubMed Central. Effect of raw milk on lactose intolerance: a randomized controlled pilot study Whatever people may feel they experience, the controlled data do not support the idea that raw milk is easier on lactose-intolerant guts.
Does Raw Milk Protect Itself
Raw milk contains natural antimicrobial systems, and raw milk advocates sometimes argue that these make the milk self-protecting. The lactoperoxidase system, which uses an enzyme naturally present in milk along with thiocyanate and hydrogen peroxide, does have genuine antibacterial activity against a range of organisms.15PubMed. Effects of bovine milk lactoperoxidase system on some bacteria And fresh raw milk has been shown to inhibit Listeria monocytogenes growth at body temperature (37°C), with the pathogen becoming undetectable after 56 hours of incubation under those conditions.16Biotechnology: Food and Health for the 21st Century. Antibacterial activity of fresh raw milk against Listeria monocytogenes
But here’s where the reality gets uncomfortable for the self-protection narrative. That same study found no inhibition of Listeria at refrigerator temperatures (4°C or 7°C), and the antimicrobial effect weakened the longer the milk was stored. Since raw milk sold to consumers is refrigerated and often days old by the time it’s consumed, the conditions under which these natural defenses actually work don’t match how people use the product. A study that inoculated raw milk with common pathogens and stored it at 4.4°C found that while Campylobacter, E. coli O157:H7, and Salmonella did not grow over 14 days, Listeria monocytogenes did grow in the majority of replicates during the second week of storage.17PubMed Central. Suppression of pathogens in properly refrigerated raw milk Refrigeration suppresses some pathogens but gives Listeria room to multiply.
Can Good Farm Practices Make Raw Milk Safe
The question many raw milk drinkers really want answered is not whether factory-farm milk is dangerous unpasteurized, but whether carefully produced milk from a small, clean farm can be safe. Some evidence says careful production helps considerably. A review of raw milk producers in North America and Europe found that raw milk intended for direct consumption can be produced with a high level of hygiene and safety across various farming systems.18PubMed Central. Raw milk producers with high levels of hygiene and safety Farms that focus on raw milk sales often invest in rigorous cleaning protocols, frequent testing, and faster delivery to customers.
But “can be produced safely” does not mean “is always safe.” A case study of a dairy goat farm in Thailand illustrates what can go wrong even with generally adequate nutritional quality in the milk: researchers found consistently high levels of presumptive Staphylococcus aureus and elevated somatic cell counts indicating subclinical mastitis, and antibiotic residues were detected in over half the samples.19Asian Health, Science and Technology Reports. Assessment of milking hygiene practices and raw goat milk quality: A case study of a dairy goat farm in Narathiwat Province, Thailand Subclinical mastitis means the animal appears healthy but has an udder infection shedding bacteria into the milk. You cannot spot it without testing. Even well-intentioned farms can have invisible contamination events: a cow might carry Campylobacter asymptomatically, or a brief lapse in sanitation can introduce Listeria from the environment. Good practices reduce the probability of contamination. They do not eliminate it.
Bird Flu and Raw Milk
The emergence of highly pathogenic avian influenza (H5N1) in U.S. dairy cattle in 2024 added a new wrinkle to the raw milk safety debate. Infected cows were found to shed large amounts of virus in their milk.20PubMed. Huge amounts of bird-flu virus found in raw milk of infected cows Pasteurization inactivates the virus, which is why commercially sold pasteurized milk is not considered a risk. But raw milk from an infected herd would contain live virus. A Swiss surveillance effort testing 124 raw milk vending machine samples over four months found no influenza A virus, suggesting the risk varies by region and herd status.21Dairy. No Evidence for Highly Pathogenic Avian Influenza H5N1 Virus in Direct-To-Consumer Raw Cow’s Milk Samples in Switzerland The broader concern, though, is that raw milk consumers have no practical way to know whether their source herd has been exposed. H5N1 in dairy cattle is a rapidly evolving situation, and it has made raw milk consumption riskier in areas where the virus is circulating among herds.
Raw Milk Cheese Is a Different Conversation
Many people encounter unpasteurized dairy not as a glass of milk but as aged cheese. Raw milk cheeses are valued for their complex flavors, and consumers consistently prefer them over pasteurized-milk versions in sensory evaluations, with taste being the most important factor driving purchases.22Revista do Instituto de Laticínios Cândido Tostes. Consumer-based sensory characterization and preference of raw and pasteurized milk cheeses In many countries, raw milk cheeses are legal and widely sold, often with a requirement that hard cheeses be aged at least 60 days before sale. The aging process, combined with acidity, salt content, and reduced water activity, creates conditions that most pathogens cannot survive in.
Soft cheeses are a different story. A study of soft lactic cheese made from raw goat milk found that while the cheesemaking process reduced Listeria monocytogenes counts, the pathogen survived throughout manufacture, ripening, and storage.23PubMed. Survival of Listeria monocytogenes during manufacture, ripening and storage of soft lactic cheese made from raw goat milk This is why food safety authorities around the world tend to be more cautious about soft raw-milk cheeses than hard aged ones, and why pregnant women are specifically warned against fresh soft cheeses made from unpasteurized milk.
What Raw Milk Does in the Gut
A small but growing area of research looks at how raw milk consumption affects the gut microbiome. One study tracked people over 12 weeks and found that intake of unpasteurized milk and dairy products was positively correlated with increased abundance of Lactobacillus in fecal samples. The researchers also observed a significant increase in valerate, a short-chain fatty acid associated with gut health.24PubMed Central. Recipe for a Healthy Gut: Intake of Unpasteurised Milk Is Associated with Increased Lactobacillus Abundance in the Human Gut Microbiome This fits with what we know about raw milk’s microbial cargo: it contains live Lactobacillus and other lactic acid bacteria that could, at least temporarily, shift the composition of gut microbes.
Whether that shift translates to improved health outcomes is an open question. The gut microbiome field is still working out which changes are beneficial, which are neutral, and which are fleeting. A bump in Lactobacillus sounds good because the genus appears in many probiotic supplements, but the clinical significance of a dietary increase from raw milk, as opposed to from fermented foods like yogurt that carry no pathogen risk, has not been established. It is an interesting finding sitting in the gap between microbiome measurement and clinical meaning.
Bacterial Counts and What They Tell You
If you’ve ever seen raw milk test results, you may have encountered total plate counts (TPC) and coliform counts. These numbers give a rough picture of how many bacteria are in the milk. A study comparing pasteurized, unpasteurized, and raw milk in Kathmandu found that unpasteurized milk had a mean total plate count about 20 times higher than pasteurized milk, and E. coli was isolated from 40 percent of unpasteurized samples compared with about 19 percent of pasteurized ones.25Tribhuvan University Journal of Microbiology. Bacterial Analysis of Different Types of Milk (Pasteurized, Unpasteurized and Raw Milk) Consumed in Kathmandu Valley High coliform counts don’t necessarily mean pathogens are present, but they indicate sanitary conditions during milking, handling, or storage that allow fecal-origin bacteria to thrive. For consumers buying directly from farms, asking about test results is reasonable, but even clean results from one batch don’t guarantee the next batch will be the same.
The microbial composition of raw milk also shifts with the seasons. Both bacterial diversity and the relative abundance of specific genera change throughout the year, influenced by temperature, humidity, feed, and housing conditions.1Scientific Reports. Variation in Raw Milk Microbiota Throughout 12 Months and the Impact of Weather Conditions A farm that tests clean in winter might have higher pathogen loads in summer, or vice versa. This variability is part of what makes raw milk inherently harder to guarantee as safe compared with a product that goes through a consistent kill step.
Goat, Sheep, and Camel Milk
Raw milk conversations usually center on cow’s milk, but the same safety principles apply to milk from goats, sheep, camels, and other animals. Goat milk has a reputation for being more digestible due to its smaller fat globules and slightly different protein structure. Camel milk has attracted attention for its higher levels of certain antimicrobial proteins and potential benefits for glycemic control, though most of that research is still preliminary. The microbiological risks, however, are comparable across species. Campylobacter, Listeria, E. coli, and Staphylococcus aureus can all be present in unpasteurized goat or sheep milk, and the same hygiene challenges apply to small ruminant dairies as to cattle operations. If anything, small-scale goat and sheep dairies may face additional challenges because the animals are often milked with less automated equipment and in closer contact with soil and vegetation where environmental pathogens live.