Is Type 1 Diabetes Triggered by the Bovine Insulin in Milk?

The tight correlation among countries between the incidence of type 1 diabetes in children and cow’s milk consumption didn’t account for Iceland. Indeed, studies correlating dairy intake in children and adolescents with the incidence of type 1 diabetes deliberately excluded the Icelandic data. Why? Is it because of genetics? Perhaps, yes and no. The people of Iceland are similar genetically to other Nordic countries, but their cows are not. As I discuss in my video Does Bovine Insulin in Milk Trigger Type 1 Diabetes?, there are two main types of the cow milk protein casein: A1 and A2. Icelandic cattle, who “have been isolated from interbreeding with other cattle breeds for over 1,100 years,” are unusual in that they produce mostly A2 milk, which may explain the lower incidence of type 1 diabetes in Iceland.

Unlike A2 casein, A1 casein breaks down into casomorphin, which has opioid properties that may alter immune function, perhaps increasing susceptibility to infections that may themselves trigger type 1 diabetes. That’s what’s in the milk from the classic black-and-white patterned Holstein cows, who make up about 95 percent of the U.S. dairy herd and much of the global herd—A1 casein. This issue has even caused dairy boards to begin taking out patents on methods for selecting “nondiabetogenic” milk to avoid triggering of Type 1 diabetes. Indeed, looking only at A1 casein consumption certainly restores that tight linear relationship between milk intake and type 1 diabetes and you can see at 1:47 in the video.

These so-called ecological, or country-by-country, studies, however, primarily serve to suggest possibilities that then need to be put to the test. For example, a study was designed where hundreds of siblings of type 1 diabetics were followed for about ten years and found that those who drank a lot of milk did have about five times the risk of coming down with the disease, too. By the mid-1990s, more than a dozen such studies were done.

Overall, researchers found that early cow’s milk exposure appears to increase the risk of type 1 diabetes by about 50 percent. Those data were enough for the American Academy of Pediatrics to decide that “cow’s milk protein may be an important factor” in the initiation of the process that destroys our insulin-producing cells. The organization went on to say that the avoidance of cow’s milk protein may reduce or delay the onset of type 1 diabetes. As such, the American Academy of Pediatrics emphasizes that breast milk is best and, for those at higher risk of the disease, strongly encourages the avoidance of products containing cow’s milk protein that is intact, as opposed to hydrolyzed formula where the milk proteins are broken up into tiny pieces.

Typically, hydrolyzed formula is given to children with dairy allergies and could potentially make it less risky, but we don’t know until we put it to the test. Based on the population studies and meta-analyses of antibody studies, which suggested that “cow’s milk may serve as a trigger of Type 1 diabetes,” a pilot study was initiated the following year. Researchers wanted to see if babies at high genetic risk for the disease would be less likely to develop antibodies that would then attack their own pancreas if they drank hydrolyzed casein—that is, casein that was chopped up. The hydrolyzed formula did seem to reduce the appearance of at least one autoimmune antibody, but not two or more, which is much more predictive of the development of the disease.

Nevertheless, that was enough for the investigators to embark on the ambitious Trial to Reduce Incidence of Diabetes in Genetically at Risk, also known as the TRIGR study. This multinational, randomized prospective trial involved randomizing thousands of newborns across 15 countries. In 2010, preliminary data suggested the hydrolyzed formula may have helped, but they didn’t quite reach statistical significance, approximately meaning there was greater than a 1 in 20 chance the findings could have just been a fluke. Indeed, when the final autoimmune antibody results were published, the special hydrolyzed formula didn’t seem to help at all.

The researchers only looked at a special group of children, though—ones who were at high genetic risk with diabetes running in the family—whereas the great majority of children who get type 1 diabetes do not have any afflicted close relative. Perhaps most importantly, however, as the researchers themselves emphasized, their study wasn’t designed to test whether cow’s milk is or is not a trigger for the disease. Instead, it aimed to analyze the potential effects of the hydrolyzed casein formula. Maybe it’s not the casein, though. Maybe it’s the bovine insulin.

Insulin autoantibodies—antibodies our body produces to attack our own insulin—often appear as the first sign in prediabetic children. “Because cow’s milk contains bovine insulin,” around the same time researchers were looking into casein, another team “followed the development of insulin-binding antibodies in children fed with cow’s milk formula.” They found significantly more antibodies to bovine insulin in the cow’s milk formula group compared to the exclusively breastfed group, who may have only been exposed to cow proteins through their mom’s breast milk (if their mothers consumed dairy). Furthermore, the bovine antibodies cross-reacted with human insulin, potentially being that caught-in-the-crossfire cause triggering at least some cases of type 1 diabetes.

Of course, we can’t know for sure until we put it to the test. Researchers ran another randomized, double-blind trial, but, this time, tried a cow’s milk formula from which the bovine insulin had been removed. And, indeed, without the bovine insulin exposure, the children built up significantly fewer autoimmune antibodies. What we don’t know yet is whether this will translate into fewer cases of diabetes.


You may also want to check out:

For more on the concerns with cow’s milk exposure in infancy and childhood, see:

I’ve developed a six-part series on the role of gluten-free, casein-free diets in the treatment of autism:

What’s The Best Baby Formula? Breast milk!

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:

Milk Consumption Is Linked to Type 1 Diabetes

Type 1 diabetes, which typically strikes children and young adults, is an autoimmune disease in which our own immune system attacks and destroys the insulin-producing cells of our pancreas. Untreated it’s deadly, but even with well-managed insulin replacement, it may shorten life expectancy by a decade. “Families are devastated when a child receives a diagnosis of type 1 diabetes…Thus, one of modern medicine’s ‘holy grails’” is to understand what causes the body to attack itself, in the hopes that we can cure or prevent the disease. Genetic susceptibility plays an important role, but the “concordance for type 1 diabetes is only about 50% among identical twins.” So, even if someone with our exact same DNA gets the disease, there’s only about a 50 percent chance we will get it, too—meaning there must be external factors as well.

Some countries have low rates of incidence, and others have high rates. Japan, for example, has type 1 diabetes rates 18 times lower than the United States. This disparity isn’t due only to genetics, however, because, when children migrate, they tend to acquire the risk of their new home, suggesting it’s got something to do with the environment, diet, or lifestyle. In fact, the incidence rates vary more than 350-fold around the world. Some countries have rates hundreds of times higher than others, and it is on the rise. Researchers looked at 37 populations from around the world and found that the incidence has been increasing about 3 percent a year—our genes don’t change that fast. In fact, they couldn’t find a single population with decreasing incidence of type 1 diabetes.

Something is going on that started around the end of World War II. “The best evidence available suggests that childhood diabetes [also known as type 1 diabetes] showed a stable and relatively low incidence over the first half of the 20th century, followed by a clear increase that began…around…the middle of the century.” Why the increase, though? A number of factors have been postulated, including vitamin D deficiency, certain infections, or exposure to cow’s milk.

Decades ago, published cross-country comparisons showed a tight correlation between milk consumption and the incidence of  type 1 diabetes. The “analysis showed that 94% of the geographic variation in incidence might be explained by differences in milk consumption.” Investigators in Finland, the country with the highest rates of type 1 diabetes and cow’s milk consumption, led much of the research into this area.

It all started with studies like the one I feature in my video Does Casein in Milk Trigger Type 1 Diabetes?, showing that the less babies are breastfed, the higher the rates of type 1 diabetes, leading to the obvious conclusion that “[b]reast-milk protects the newborn infant.” On the other hand, if babies are not getting breast milk, they’re getting formula, which probably contains cow’s milk proteins. In the first few months of life, our gut is especially leaky to proteins. Is it possible that as our immune system attacks the foreign cow proteins, our pancreas gets caught in the crossfire? This was based on animal experiments, however. In susceptible mice, a diet containing the cow’s milk protein, casein, produced diabetes, but it did not cause diabetes in rats. So, are we more like mice or rats?

Researchers drew blood from children with type 1 diabetes to see if they had elevated levels of antibodies that attack bovine proteins compared to controls. Their finding? Every single child with type 1 diabetes had elevated anti-bovine protein antibodies circulating in their blood compared to much lower levels in the control subjects. That seems pretty convincing, but what about Iceland? They drink more milk in Iceland than in Finland, yet Icelanders have less than half the type 1 diabetes. I explore this paradox in my follow-up video Does Bovine Insulin in Milk Trigger Type 1 Diabetes?.


The vast majority of diabetes cases are type 2, so that’s been my concentration:

I’m pleased to have been able to address type 1 diabetes. For even more on this disease, see:

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:

Where Vitamin D Supplements Fail

As I discuss in my video Do Vitamin Supplements Help with Diabetes, Weight Loss, and Blood Pressure?, review articles continue to be published touting vitamin D as a veritable cure-all. The vitamin D receptor is found in most tissues in the body, including the brain, and upwards of 2,000 genes may be regulated by vitamin D. Within 24 hours of vitamin D exposure, we can change the expression of hundreds of genes.

The term vitamin is a misnomer, though, because vitamins by definition cannot be synthesized within our body, but we can make all the D we need with sufficient sun exposure. So, rather than a vitamin, D is actually a hormone that’s produced by our skin in response to sunlight exposure. D is not just a hormone of calcium regulation and bone health; it’s also a hormone of fertility, immunity, and brain function. But is it a panacea or a false prophet?

Remember when vitamin E was the vitamin du jour, touted as a “curative for many clinical disorders”? Supplement sales of vitamin E, the “radical protector,” created a billion-dollar business that capitalized on the public’s fears. After all, those with low levels of vitamin E in their blood had a 50 percent higher cancer risk. Similar attention was directed towards vitamin A or beta-carotene. People who eat lots of greens, sweet potatoes, and other beta-carotene-rich foods have lower risk of cancer, so maybe we should give people beta-carotene pills? When they were put to the test, however, beta-carotene pills actually increased cancer rates. In fact, beta-carotene, vitamin A, and vitamin E supplements all may increase mortality, so when we buy these supplements, we’re potentially paying to shorten our lifespans. As such, I imagine you can understand the skepticism in the medical community regarding claims about vitamin D, which is now enjoying its moment in the sun.

Having a half-billion-dollar vitamin D supplement industry doesn’t help matters in terms of getting at the truth. And there’s also a highly lucrative vitamin D testing industry that loves to talk about the studies suggesting that having higher vitamin D levels may reduce the risk of heart disease, cancer, diabetes, autoimmune diseases, and infections. Most of this research, however, stems from observational studies, meaning studies that correlate higher D levels in the blood with lower disease risk, but that doesn’t mean vitamin D is the cause. It’s like the early beta-carotene data: Higher levels in the blood may have just been a marker of healthy eating. Who has high beta-carotene levels? Those who eat lots of greens and sweet potatoes. Similarly, higher levels of vitamin D may just be a marker of healthy behaviors. Who has high vitamin D levels? Those who run around outside, and those who run around outside, run around outside. Indeed, higher vitamin D levels may just be a sign of higher physical activity.

So, for instance, when you see studies showing significantly lower diabetes rates among those with higher vitamin D levels, it doesn’t mean giving people vitamin D will necessarily help. You have to put it to the test.  And, when you do, vitamin D supplements fall flat on their face, showing no benefit for preventing or treating type 2 diabetes.

So, when supplement companies wave around studies suggesting vitamin D deficiency plays a role in obesity, because most population studies show that obese individuals have lower vitamin D levels in their blood, is that simply because they’re exercising less or because it’s a fat-soluble vitamin so it’s just lodged in all that fat? We might expect obese sunbathers to make more vitamin D, since they have more skin surface area, but the same exposure level for them leads to less than half the D bioavailability, because it gets socked away in the fat. This is why obese people may require a dose of vitamin D that’s two to three times higher than normal weight individuals, although they may get it back if they lose weight and release it back into their circulation. This would explain the population data. Indeed, when you put vitamin D to the test as a treatment for obesity, it doesn’t work at all.

It’s a similar story with artery health. Those with low vitamin D levels have worse coronary blood flow, more atherosclerosis, and worse artery function, but if you actually put it to the test in randomized controlled trials, the results are disappointing. Vitamin D is also ineffective in bringing down blood pressures.

This all adds to the growing body of science “casting doubt on the ability of vitamin D supplementation to influence health outcomes beyond falls, fractures, and possibly respiratory tract infection and all-cause mortality.” Wait. What? Vitamin D supplements may make you live longer? That’s kind of important, don’t you think? I talk about that in my video Will You Live Longer If You Take Vitamin D Supplements?.


Explore the other videos in my series on vitamin D, including:

And check out these other videos on vitamin D’s potential benefits:

For additional videos on supplements, see:

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: