The Role of Meat and Dairy in Triggering Type 1 Diabetes

Type 1 diabetes “arises following the autoimmune destruction of the insulin-producing pancreatic β [beta] cells…[and] is most often diagnosed in children and adolescents, usually presenting with a classic trio of symptoms” as their blood sugars spike: excessive thirst, hunger, and urination. They need to go on insulin for the rest of their lives, since their own immune systems attacked and destroyed their ability to produce it. What would cause our body to do such a thing? I examine this in my video, Does Paratuberculosis in Milk Trigger Type 1 Diabetes?

Whatever it is, it has been on the rise around the world, starting after World War 2. “Understanding why and how this produced the current pandemic of childhood diabetes would be an important step toward reversing it.” A plausible guess is “molecular mimicry, whereby a foreign antigen (bacterial or viral) provokes an immune response, which cross-reacts” with a similar-looking protein on our pancreas such that when we attack the bug, our own organ gets caught in the cross-fire. Given this, what pancreatic proteins are type 1 diabetics self-attacking? In the 1980s, a protein was identified that we came to realize in the 1990s looked an awful lot like a certain mycobacterial protein. Mycobacteria are a family of bacteria that cause diseases like tuberculosis and leprosy, and, in one study, all newly diagnosed type 1 diabetic children were found to have immune responses to this mycobacterial protein. This didn’t make any sense as incidence of type 1 diabetes has been going up in the industrialized world, whereas TB and leprosy rates have gone down. However, there is one mycobacterial infection in farm animals that has shot up with the industrialization and globalization of animal agriculture: paratuberculosis (paraTB), which causes Johne’s disease in animals. Paratuberculosis is now recognized as a global problem for the livestock industry.

Weren’t there a dozen or so studies suggesting that “cow’s milk exposure may be an important determinant of subsequent type 1 diabetes” in childhood? Indeed. After putting two and two together, an idea was put forward in 2006: Could mycobacterium paratuberculosis from cattle be a trigger for type 1 diabetes? The idea was compelling enough for researchers put it to the test.

They attempted to test the association of Mycobacterium avium paratuberculosis (MAP), the full name for the bug, with type 1 diabetes by testing diabetics for the presence of the bacteria in their blood. Lo and behold, most of the diabetic patients tested positive for the bug, compared to only a minority of the healthy control subjects. This evidence of MAP bacteria in the blood of patients with type 1 diabetes “might provide an important foundation in establishing an infectious etiology,” or cause, for type 1 diabetes. “These results also might possibly have implications for countries that have the greatest livestock populations and high incidence of MAP concurrent with the highest numbers of patients with” diabetes, like the United States.

Johne’s is the name of the disease when farm animals get infected by MAP. The reason diabetes researchers chose to look at Sardinia, an island off the coast of Italy, is because paratuberculosis is present in more than 50 percent of Sardinian herds. Surpassing that, though, is the U.S. dairy herd. According to a recent national survey, 68 percent of the U.S. dairy herd are infected with MAP, especially those cattle at big, industrial dairies, as you can see at 3:33 in my video. Ninety-five percent of operations with more than 500 cows came up positive. It’s estimated the disease costs the U.S. industry more than a billion dollars a year.

How do people become exposed? “The most important routes of access of MAP to the [human] food chain appear to be contaminated milk, milk products and meat” from infected cattle, sheep, and goats. MAP or MAP DNA has been detected in raw milk, pasteurized milk, infant formula, cheese, ice cream, muscle and organ tissues, and retail meat. We know paraTB bacteria survive pasteurization because Wisconsin researchers bought hundreds of pints of retail milk off store shelves from three of the top U.S. milk-producing states and tested for the presence of viable, meaning living, MAP bacteria. They found that 2.8 percent of the retail milk tested came back positive for live paraTB bacteria, with most brands yielding at least one positive sample. If paraTB does end up being a diabetes trigger, then “these findings indicate that retail milk [in the United States] would need to be considered as a transmission vector.” Why hasn’t the public heard about this research? Perhaps because the industry is not too keen on sharing it. Indeed, according to an article in the Journal of Dairy Science: “Fear of consumer reaction…can impede rational, open discussion of scientific studies.”

Not only is MAP a serious problem for the global livestock industry, but it also may trigger type 1 diabetes, given that paraTB bacteria have been found in the bloodstream of the majority of type 1 diabetics tested who presumably are exposed through the retail milk supply as the bacteria can survive pasteurization. But what about the meat supply? MAP has been found in beef, pork, and chicken. It’s an intestinal bug, and unfortunately, “[f]aecal contamination of the carcass in the abattoir [slaughter plant] is unavoidable…” Then, unless the meat is cooked well-done, it could harbor living MAP.

In terms of meat, “ground beef represents the greatest potential risk for harboring MAP…[as] a significant proportion originates from culled dairy cattle,” who may be culled because they have paratuberculosis. These animals may go straight into the human food chain. There also exists greater prevalence of fecal contamination and lymph nodes in ground meat, and the grinding can force the bacteria deep inside the ground beef burger. As such, “given the weight of evidence and the severity and magnitude of potential human health problems, the precautionary principle suggests that it is time to take actions to limit…human exposure to MAP.” At the very least, we should stop funneling animals known to be infected into the human food supply.

We know that milk exposure is associated with type 1 diabetes, but what about meat? As I discuss in my video Meat Consumption and the Development of Types 1 Diabetes, researchers attempted to tease out the nutritional factors that could help account for the 350-fold variation in type 1 diabetes rates around the world. Why do some parts of the world have rates hundreds of times higher than others? Yes, the more dairy populations ate, the higher their rates of childhood type 1 diabetes, but the same was found for meat, as you can see at 2:07 in my video. This gave “credibility to the speculation that the increasing dietary supply of animal protein after World War II may have contributed to the reported increasing incidence of type 1 diabetes…” Additionally, there was a negative correlation—that is, a protective correlation that you can see at 2:26 in my video—between the intake of grains and type 1 diabetes, which “may fit within the more general context of a lower prevalence of chronic diseases” among those eating more plant-based diets.

What’s more, the increase in meat consumption over time appeared to parallel the increasing incidence of type 1 diabetes. Now, we always need to be cautious about the interpretation of country-by-country comparisons. Just because a country eats a particular way doesn’t mean the individuals who get the disease ate that way. For example, a similar study looking specifically at the diets of children and adolescents between different countries “support[ed] previous research about the importance of cow’s milk and [other] animal products” in causing type 1 diabetes. But, the researchers also found that in countries where they tended to eat the most sugar, kids tended to have lower rates of the disease, as you can see at 3:18 in my video. This finding didn’t reach statistical significance since there were so few countries examined in the study, but, even if it had and even if there were other studies to back it up, there are countless factors that could be going on. Maybe in countries where people ate the least sugar, they also ate the most high fructose corn syrup or something. That’s why you always need to put it to the test. When the diets of people who actually got the disease were analyzed, increased risk of type 1 diabetes was associated with milk, sugar, bread, soda, eggs, and meat consumption.

In Sardinia, where the original link was made between paraTB and type 1 diabetes, a highly “statistically significant dose-response relationship” was found, meaning more meat meant more risk, especially during the first two years of children’s lives. So, “[h]igh meat consumption seems to be an important early in life cofactor for type 1 diabetes development,” although we needed more data.

The latest such study, which followed thousands of mother-child pairs, found that mothers eating meat during breastfeeding was associated with an increased risk of both preclinical and full-blown, clinical type 1 diabetes by the time their children reached age eight. The researchers thought it might be the glycotoxins, the AGEs found in cooked meat, which can be transferred from mother to child through breastfeeding, but they have learned that paratuberculosis bacteria can also be transferred through human breast milk. These bacteria have even been grown from the breast milk of women with Crohn’s disease, another autoimmune disease linked to paraTB bacteria exposure.


For a deeper discussion of other possibilities as to why cow’s milk consumption is linked to this autoimmune destruction of insulin production, see Does Casein in Milk Trigger Type 1 Diabetes? and Does Bovine Insulin in Milk Trigger Type 1 Diabetes?.

If we don’t drink milk, though, what about our bone health? See my videos Long-Term Vegan Bone Health and Is Milk Good for Our Bones?.

The vast majority of cases of diabetes in the United States are type 2, though. Ironically, meat may also play a role there. See my videos Why Is Meat a Risk Factor for Diabetes? and How May Plants Protect Against Diabetes? for more information.

For more on the links between milk and diabetes, see my videos Does Casein in Milk Trigger Type 1 Diabetes? and Does Bovine Insulin in Milk Trigger Diabetes?. What about treating and preventing diabetes through diet? Check out How Not to Die from Diabetes and How to Prevent Prediabetes from Turning Into Diabetes.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Cow Cancer Virus Implicated in Breast Cancer

Up to 20 percent of all cancers in general are linked to infections, particularly viruses, and the list of potentially carcinogenic infectious agents is growing. It would be great if we could find a virus that contributed to breast cancer risk, because then we might have new ways to prevent and treat it. Currently, the dietary link between breast cancer and consumption of meat and dairy is considered a saturated fat effect, but there is a cancer-causing bovine virus that infects the mammary gland cells of cows. The infectious virus is then released into the milk supply. Since most U.S. dairy herds are infected, scientists posit that Americans are often exposed to this bovine leukemia virus (BLV), which I discuss in my video The Role of Bovine Leukemia Virus in Breast Cancer.

We didn’t have proof of this until 2003, 34 years after the virus was first identified. Early on, our best available tests failed to find antibodies to BLV in human blood. When our immune system is exposed to a virus, it creates antibodies to attack it. No antibodies, no exposure. “This led to the prevailing opinion that…the virus is not a public health hazard.” Though those tests “were state of the art at that time, they are extremely insensitive compared to more modern techniques.” As a result, researchers decided to re-examine the issue now that we have better tests. They took blood from about 250 people simply to address the question: “Do any humans have antibodies to BLV?” The answer? Yes, 191 of them did––74 percent. That shouldn’t have come as a surprise, however: By then, nearly 90 percent of American dairy herds were infected, and, according to the latest national survey, 100 percent of the big factory dairy farms were infected, as determined by testing the milk coming from those operations. Given this, why isn’t there an epidemic of cancer of the udder? Dairy cattle are slaughtered so young that there isn’t a lot of time for them to develop gross tumors, but that’s how most women may be getting infected. Although pasteurization should knock out the virus, who hasn’t eaten a rare, pink-in-the-middle burger at some point?

The bottom line is that the “long-held assumption that BLV is not a public health hazard…is no longer tenable…” This whole field of investigation needs to be reopened, with the next step determining whether humans are actually infected. “The presence of antibodies to particular viruses in human sera is generally interpreted as an indicator of a present or past infection with the virus.” But, theoretically, we might have developed antibodies to the dead viruses we ate, viruses that had been killed by cooking or pasteurization. Just because three-quarters of us have been exposed doesn’t mean we were actively infected by the virus.

How do we prove this? We would need to find the retrovirus actively stitched into our own DNA. Well, millions of women have had breast surgery, so why not just look at the tissue? Researchers finally did just that and published their findings in the Centers for Disease Control and Protection’s emerging infectious diseases journal: Forty-four percent of samples tested positive for BLV, proving for the first time that humans can be infected with bovine leukemia virus. The final step? Determine whether the virus is actually contributing to disease. In other words, are the bovine leukemia viruses we’re finding in human breast tissue cancer-causing or just “harmless passengers”?

One way to make that determination is to see whether the virus is more often present in those with breast cancer. No one had ever looked for the virus in breast tissue from people with cancer…until now. The “[p]resence of BLV-DNA in breast tissues was strongly associated with diagnosed and histologically confirmed breast cancer…” As many as 37 percent of human breast cancer cases may be attributable to exposure to bovine leukemia virus.


For some historical background leading up to these shocking findings, see my video Is Bovine Leukemia Virus in Milk Infectious?.

I couldn’t wait to read the meat and dairy industry journals to see how they’d try to spin this. Find out what I discovered in my final video in this series Industry Response to Bovine Leukemia Virus in Breast Cancer.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Should You Be Concerned about Bovine Leukemia Virus in Milk?

Decades ago, concern was raised that the milk of dairy cows frequently contains a leukemia-causing virus—more specifically, bovine leukemia virus (BLV), the leading cancer killer among dairy cattle. Most U.S. dairy herds are infected with the cancer virus. “Thus the question of whether dairy cows naturally infected with BLV release infectious virus into milk is an important public health consideration” and the subject of my video Is Bovine Leukemia Virus in Milk Infectious?.

Researchers at the University of Pennsylvania decided to put it to the test. And indeed, infectious virus was demonstrated in the milk of 17 of the 24 cows tested, indicating that “humans are often orally exposed to BLV.” Just because we’re exposed to it doesn’t mean it’s causing human disease, though. How do we know BLV can even infect human cells? We didn’t until 1976 when it was discovered that BLV can indeed infect human, chimpanzee, and rhesus monkey cells. Nevertheless, that still doesn’t mean BLV necessarily causes cancer in other species.

Researchers can’t lock human infants in a cage and feed them infected milk, but they can cage infant chimpanzees. Chimps Bois and Roger were fed infected milk, developed leukemia, and died. Until then, we didn’t even know chimps could get leukemia. The fact that BLV-infected milk appeared to transmit or induce leukemia in our closest living relatives certainly did raise the stakes, but human beings are not chimpanzees. Yes, our DNA may be 98 percent identical, but we may share 60 percent of our DNA with a banana. We need human studies.

We can’t do interventional trials in this case, thanks to those pesky Nuremberg principles, but what about observational studies? Do cattle farmers have higher rates of cancer? Apparently so. This finding led some to suggest that “milk- and egg-borne viruses may be highly important in the pathogenesis [or development] of human leukemia and lymphoma,” but farmers may be exposed to all sorts of potential carcinogens, such as pesticides. Large animal veterinarians may also have more leukemia and lymphoma, but some are also “particularly lax in the use of X-ray protective equipment,” so it didn’t necessarily have anything to do with viruses.

We needed so-called serology studies, testing people’s blood for antibodies against the virus, which would prove human exposure, and we got them. Ten different studies looked for BLV antibodies in cancer patients and non-cancer patients, creamery employees versus office employees, veterinarians, unpasteurized milk drinkers, and more. “Not one of these studies found a single individual with antibodies to BLV…” As a result, in 1981, the case was closed: “Therefore, there is strong serological evidence to indicate that BLV is not transmissible to man.” However, the strength of the evidence is only as strong as the strength of the test. Chimpanzees Bois and Roger didn’t develop detectable antibodies either, and they died from BLV.

The tests available a handful of decades ago were not really sensitive. “Clearly, the question of whether BLV poses a public health hazard deserves thorough investigation” using highly sensitive molecular probes. It would take a few decades for us to get such an examination, and I discuss those landmark findings in my videos The Role of Bovine Leukemia in Breast Cancer and Industry Response to Bovine Leukemia Virus in Breast Cancer.


Thankfully, feline leukemia virus does not appear to be transmissible. See Pets and Human Lymphoma.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: