Thousands of years ago, after domesticating cows and other ruminants, humans did something remarkable: They began to consume the milk from these animals. Scientists consider mammalian milk to confer a tremendous evolutionary advantage because it allows mothers to feed immature offspring with food well tailored to their needs. With the advent of dairying, humans inserted themselves into this ancient relationship between ruminant mothers and their offspring, diverting this source of nutrition into their own bodies.
By consuming the milk of ruminants — possibly after fermenting it — humans found a reliable way to nourish themselves with grass and other tough plant material that they themselves couldn’t digest directly. As a cultural adaptation, dairying was so important, one scientist told me, that whoever invented it deserves to win a Nobel Prize posthumously. Every year.
But living closely with animals and drinking their milk also presents risks, chief among them the increased likelihood that infections will jump from animals to people. Some of humanity’s nastiest scourges, including smallpox and measles, probably originated in domesticated animals. In the 19th century, as industrialization spurred urbanization and mass migration, milk became a major vector of disease. As late as 1938, illnesses from milk still accounted for one-quarter of all infectious diseases contracted from what people ate and drank that year. During this period, newly established health authorities began pushing for milk to be treated by heating it; this simple practice of pasteurizing milk would come to be considered one the great public-health triumphs of the modern era.
Today, however, a small but growing number of Americans prefer to drink their milk raw. And Robert F. Kennedy Jr., Donald Trump’s choice to lead the Department of Health and Human Services, now stands at the vanguard of this movement. Kennedy has said he drinks raw milk and has criticized what he describes as the Food and Drug Administration’s “aggressive suppression” of raw-milk production, among other things. Enthusiasts anticipate that, as H.H.S. secretary, he would make raw milk easier to acquire — although how remains unclear. Federal regulations prohibit the sale of raw milk across state lines, but where it’s legal, raw milk is regulated by state governments, not federal agencies.
In embracing raw milk, Kennedy is following an established trend as much as leading it. The roots of the movement stretch back decades. The small, independent health-food stores my parents frequented in New Mexico in the 1980s, for example, sold raw milk. (We never partook.) But to hear Mark McAfee tell it, the pandemic supercharged demand.
McAfee heads one of the largest producers of raw milk in the country, Raw Farm in California. McAfee, who has said Kennedy is a customer, has applied to serve in an advisory role at H.H.S. — at the urging of Kennedy’s transition team, he says. During the pandemic, McAfee told me, people felt abandoned by medical professionals and began researching ways to care for their own immune systems. Many turned to raw milk, which he calls “the first food of life.” Maybe they thought it could protect them from the coronavirus, he says, an unproven idea that may stem from the observation that human breast milk provides nursing infants with some protection against infection.
Anecdotes of seemingly miraculous cures from raw milk also help fuel the phenomenon — inflammatory diseases that go into remission, allergies and digestive problems that disappear. McAfee eagerly shared such stories. Nonetheless, his customers defy easy categorization. When he began selling raw milk 25 years ago, hippie “nut-and-berry moms” and natural foodies, as he puts it, formed McAfee’s core clientele. But as his sales have grown — about 30-fold since then, he estimates — his customers have diversified.
Today’s raw-milk movement is made up of people and ideas from across the political spectrum: back-to-the-land types seeking unadulterated whole foods; health fanatics seeking the latest superfood; don’t-tell-me-what-to-eat libertarians who distrust authority and who, in McAfee’s description, intend to do the opposite of whatever the F.D.A. says. A variety of labels have been applied to the movement: “food sovereignty,” “slow food,” “real food,” “food freedom.” For the more conspiratorially minded, raw milk represents food free of government meddling. For those merely chasing the latest fad, raw milk may be a status symbol — a single gallon can cost nearly $20.
There are numerous reasons to be skeptical about these claims and the fervor behind them, not least of which is that unpasteurized dairy products are 840 times as likely as their pasteurized counterparts to lead to infection and illness, according to the Centers for Disease Control and Prevention. (For all the care McAfee says he takes, health authorities have linked his dairy with several disease outbreaks over the years, and the government has pursued legal action against him in the past. McAfee says the F.D.A. is simply bent on suppressing raw milk.)
And yet there is also a wealth of epidemiological research, most of it from Europe, that suggests that drinking raw milk early in life can protect against the development of asthma and allergies later. Even if this science does not indicate that raw milk can cure disease, but only prevent certain conditions from developing, the basic notion animating the raw-milk movement — that something good and healthful is lost during processing — may have some validity to it.
No researcher I spoke with, including the scientists most familiar with the putative benefits of raw milk, recommended that people drink it. The risks are too great to be offset by the possible benefits. Between 1998 and 2018, at least 2,645 people fell ill after drinking raw milk, according to data from the Centers for Disease Control and Prevention; 228 of them were hospitalized; three died. (More than 200 people have been sickened in outbreaks since then, according to the C.D.C.’s National Outbreak Reporting System, which doesn’t include all cases.) And as the H5N1 bird flu has infected dairy herds across the country in recent months — with the first human fatality, most likely from direct contact with infected birds, coming in the first week of January — public-health experts have become increasingly concerned that consumers could contract the virus from raw milk.
Yet these cautions shouldn’t obscure the importance of what these same scientists may have uncovered. Over the course of the 20th century, a rising tide of allergic diseases engulfed the developed world. Children seemed increasingly vulnerable to asthma, hay fever, eczema, food allergies and other allergic problems. These trends have baffled scientists. The allergens now causing so much misery, from dust mites and tree pollen to nuts and wheat, weren’t exactly new to the human experience. Why were people now so sensitive to them?
The discovery around the turn of the millennium that some groups of people were relatively resistant to this trend, including a subset of European children who were drinking raw milk, suggests there might be a fix to what is often called the allergy epidemic. Scientists think that if they can identify what’s special about raw milk, and preserve it through treatment that makes it safe, maybe they can turn a widely consumed foodstuff into a powerful tool of preventive medicine.
With Kennedy now tapped to helm H.H.S., scientists and public-health experts face a conundrum. Should they flatly deny that raw milk has any health benefits, a longstanding strategy that risks driving curious people to less reliable sources of information? Or should they try to directly address what truths might be found among this consumer movement?
The modern story of raw milk and its possible health benefits begins in the late 1990s, when Charlotte Braun-Fahrländer, then an epidemiologist at the University of Basel in Switzerland, received a tip from a local village doctor: The children of farmers seemed to suffer from allergies much less frequently than other village children.
The first study by Braun-Fahrländer and her colleagues investigating this observation, published in 1999, corroborated the village doctor’s impression, documenting a strong inverse relationship between farming and allergic disease. Children on farms were about one-third as allergic, as measured by specific antibodies in their blood and their propensity for sneezing attacks during hay-fever season, as their nonfarming peers in the same rural areas. And the more intensively their families farmed — part time versus full time — the more protected they were.
That finding sparked what has become its own small field of scientific inquiry. In the decades since, Braun-Fahrländer and others have published dozens of studies, comprising thousands of children, on what is now known as the “farm effect.” The effect has been observed on farms in Switzerland, Austria, Germany, France, Britain, Finland and, most recently, among some farming communities in the United States.
Researchers have settled on two distinct kinds of exposure that they think explain how farming may lower the risk of allergy and asthma. First is the microbially rich environment of farms with animals, particularly cows. The greater the exposure to animals, cowsheds and fermented feed, the stronger the protection against a variety of allergies. The second factor, which seems to work independently of the first, is the consumption of raw milk. Children who don’t live on farms but who might acquire raw milk from one nearby also have a lower risk of these diseases. And the earlier the initial exposures, whether to microbes or raw milk, the more protection children seem to get.
The relevant farms are generally small, family-run affairs, not the large dairying operations that tend to dominate in the United States. The distinct lifestyle is important, scientists think, for how it determines the timing and variety of exposures throughout childhood. Expectant mothers might work with animals during pregnancy; they might also consume raw milk while pregnant, and their infants might begin drinking it after they are weaned. Children might play in the cowshed, ensuring exposure to an abundance and variety of microbes well into their youth. “It’s many effects that overlay,” says Markus Ege, a scientist at the German Center for Lung Research at Ludwig Maximilian University of Munich who studies the farm effect. Together “they give a strong effect.”
The constant stimulation of immune systems in such conditions seems to set them on a specific trajectory of development. At birth, their umbilical-cord blood already contains more regulatory T-cells, thought to prevent allergy, than that of newborns in nonfarming environments. And their immune systems continue to be measurably different for years to come.
Disentangling precisely what features of an alpine farm are most important — mud, manure, fermented feed, fungi, raw milk — has been maddeningly difficult, however. Scientists I spoke with who were familiar enough with this research to comment on it knowledgeably were usually convinced that the farm effect is real, without being exactly sure how it works. Christine Seroogy, a pediatric allergist and immunologist at the University of Wisconsin-Madison who has begun to study the farm effect in the state’s Amish, Mennonite and other farming communities, doesn’t think the European studies have satisfactorily determined the extent to which raw milk alone contributes to the protective effect of farming. “I’m not ignoring their findings,” she told me. “But I think we want to understand mechanism and biology.”
The best way to prove that raw milk really does improve human health would be to give it to children from nonfarming environments and then measure their health outcomes over time compared with the health of children drinking pasteurized milk. The trouble, of course, is that getting ethical approval for such an experiment is difficult because of the risks involved. So the next best approach is to study animals.
About a decade ago, Betty van Esch, an immunologist at Utrecht University in the Netherlands, began a series of mouse studies, partly funded by Danone Research & Innovation, to ascertain whether raw milk might prevent allergy and asthma. Using untreated milk from an organic dairy farm in Germany, where the sale of raw milk is legal and regulated, she and her colleagues found that raw milk does seem to alter how the mouse immune system responds to allergens.
In a food-allergy experiment, giving mice the human equivalent of two glasses of raw milk a day for eight days greatly dampened the allergic reaction to egg protein. In another experiment meant to simulate asthma, raw milk also blunted the reaction to dust mites, a common respiratory allergen. Heat-treated milk did not have this effect. Van Esch is still investigating why. She talks about “the matrix” of milk — the fact that, as an evolutionary artifact, milk does many things at once.
Certain bioactive molecules in cow’s milk — it contains whey proteins, such as lactoferrin, that may subtly stimulate the immune system, as well as signaling molecules called cytokines and antibodies — most likely work to direct the calf’s immune system toward healthy development. And because many of these molecules are sensitive to and deformed by high temperatures, heating milk may nullify their benefits. (In a study with just nine participants, van Esch also found that children already allergic to milk were better able to tolerate raw milk than milk treated with high heat, suggesting that such processing may somehow make the milk itself more allergenic.)
Importantly, the bovine versions of the cytokines thought to help prevent allergy in human milk are close enough to their human counterparts for the human immune system to recognize and respond to them, says Joost van Neerven, an immunologist who studies milk at Wageningen University in the Netherlands. Some antibodies in cow’s milk may also bind to allergens and prevent them from spurring a reaction in people, he says; other antibodies may lessen the severity of infections like R.S.V., a virus linked to the development of asthma. (An intriguing epidemiological finding is that children on farms who drink raw milk have a 30 percent reduction in symptomatic colds in the first year of life compared with those who don’t.)
Another possible explanation for the beneficial effects associated with raw milk may be how it affects the community of microbes inhabiting farming children’s bodies. Microbiologists believe that these microbes, which mostly live in the large intestine, greatly influence how the immune system works and whether it’s prone to allergic or autoimmune diseases. And epidemiologists studying the farm effect have in fact found that children on farms tend to develop, earlier in life than their nonfarming peers, a microbiome that produces more of a metabolite called butyrate. The more butyrate produced, the lower the chance of developing asthma.
How drinking raw milk might contribute to this shift is unclear. Caroline Roduit, a pediatric allergist at the University of Bern hospital in Switzerland, posits that the combination of breast milk with the early-life introduction of raw cow’s milk may help seed children’s microbial communities with key species they don’t come by otherwise. These bugs could then enhance their ecosystems’ ability to produce butyrate and other metabolites when the children eat fiber and certain starches. Raw milk may prevent the emergence of asthma and allergic disease by essentially fine-tuning the microbiome — a kind of pharmaceutical factory within us — to children’s benefit.
All of the scientists working in this field agree that more research is needed. Erika von Mutius, director of the Institute of Asthma and Allergy Prevention at Helmholtz Munich and a senior author on many of the farm-effect studies, sketched out a best-case scenario in the current American political moment. Perhaps Kennedy’s ascension, which has already put the spotlight on raw milk, would provide “an incentive to study this more carefully,” she said.
And maybe we don’t even need to figure out the exact mechanism by which raw milk confers its benefits. Some experts told me that new processing technologies could lessen the need to heat milk, thereby preserving its mysterious protective quality — using ultraviolet radiation to kill pathogens in milk, for example, or membrane filters to remove them. Betty van Esch points out that fermenting raw milk into kefir raises acidity, which could kill off pathogens while preserving milk’s anti-allergic virtues.
Simply using less heat during treatment might be another approach. Joost van Neerven notes that higher temperatures alter what may be the key milk proteins more than lower temperatures do. Indeed, Markus Ege, Erika von Mutius and their colleagues are testing minimally heated milk in an ongoing study with children.
When it comes to the broader raw-milk movement, scientists worry that, in pursuit of uncertain benefit, aficionados will expose themselves to significant risk. Von Mutius, a pediatrician, recalls seeing earlier in her career children in the intensive-care unit sickened by food-borne illnesses. “I’m sorry, but it’s not a little side effect you have, a belly ache or something,” she told me. “The milk can be contaminated by one pathogen, cause severe disease and even kill.”
Most of the cow’s milk that has been studied comes from small alpine farms. Cows in other environments, eating different feed, do not necessarily produce milk with the same protective qualities. Moreover, anyone inspired to begin drinking raw milk might be overlooking the fact that the current evidence indicates the preventive medicinal power of raw milk probably comes from starting to drink it early in life. The farm effect research has not investigated whether there is any benefit for those who start drinking it as adults.
The movement also tends to disregard the particular immunological conditioning that occurs on farms, von Mutius says. The abundance of microbial stimuli in those settings may enhance children’s ability to fight off infectious organisms — including those found in raw milk. “They have a different immune system,” she says. “These children are much more protected.”
If it is crucial to acknowledge these sorts of nuances and uncertainties, it is also important to recognize the vein of truth running through the raw-milk movement: The health value of raw milk may be greater than the basic nourishment it provides. It may contain ingredients that benefit human health in extra-nutritional ways that haven’t received much consideration in the past, mostly because no one knew they mattered.
Now, as Kennedy and others who have long railed against the government agencies tasked with caring for Americans’ health appear set to wield influence over them, scientists face a delicate balancing act. How do they discuss frankly not just the risks but also the possible benefits of raw milk without encouraging more of the unfounded claims and misinformation that already abound?
Christine Seroogy of the University of Wisconsin told me that while she no longer thinks that scientists should dominate discussions about raw milk — “You need to have multiple stakeholders at the table,” like the families interested in drinking it, the producers, the regulators — they are still in the best position to provide guidance.
Moises Velasquez-Manoff is a writer based in California. He’s is the author of the book “An Epidemic of Absence: A New Way of Understanding Allergies and Autoimmune Diseases.” Ricardo Tomás is an illustrator and designer from Spain who is currently based in Sweden. His work focuses on simple solutions for conceptual challenges through the exploration of different techniques.
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