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The tight correlation among countries between the incidence of type 1 diabetes among children and cow milk consumption didn’t account for Iceland. So, you’ll see studies like this. “Cow’s milk…consumption [in children and adolescents was] correlated with the incidence” of type 1 diabetes—but only when they excluded the Icelandic data.

Is it just genetics? Maybe yes and no. The people of Iceland are genetically similar to other Nordic countries, but their cows are not. “Icelandic cattle have been isolated from interbreeding with other cattle breeds for over 1,100 years.” See, there are two main types of casein protein (A1 and A2), and Icelandic cattle are unusual in that they produce mostly A2 milk. And, that may explain the lower incidence of type 1 diabetes in Iceland.

See, A1 casein breaks down into casomorphin, whereas A2 casein doesn’t. And, casomorphin has opioid properties that may alter immune function—perhaps increasing susceptibility to infections that may themselves trigger type 1 diabetes. And, that’s the kind of milk you get with Holstein cows—the ones with the classic black-and-white pattern, who make up about 95% of the U.S. dairy herd, and much of the global dairy herd.

It got to a point where dairy boards began taking out patents on methods for selecting non-diabetogenic milk, to avoid triggering type 1 diabetes. It certainly did restore that tight linear relationship between milk consumption and type 1 diabetes, if you just looked at A1 casein consumption. But, these so-called “ecological [or country-by-country] studies, really only [serve to] suggest possibilities [that then need to be put to the test].” So, studies like this were designed, where hundreds of siblings of type 1 diabetics were followed for about ten years, and those that drank a lot of milk had about five times the risk of coming down with the disease, too.

By the mid-90s, more than a dozen such studies were done. And, overall, they found that “early cow’s milk exposure” appears to “increase the risk” of type 1 diabetes by about 50%. That was good enough for the American Academy of Pediatrics, who decided that “cow’s milk protein may [indeed] be an important factor in the initiation of the [process that destroys your insulin-producing cells].”

And so, “The avoidance of cow’s milk protein…may reduce…or delay [the onset of type 1 diabetes].” Yet, another reason to emphasize breast is best. For those at risk, they strongly encourage “the avoidance of…products containing intact cow’s milk protein,” as opposed to hydrolyzed formula, in which the milk proteins are all broken up into tiny pieces—which is used for kids with dairy allergies, or could potentially make it less risky. But, I mean, you don’t know, until you put it to the test.

Based on the population studies and meta-analyses of all those antibody studies, which suggested that “cow’s milk may serve as a trigger of Type 1 diabetes,” the next year, “a pilot study was initiated” to see if babies at high genetic risk would be less likely to develop antibodies that then attacked their own pancreas, if they drank casein that was chopped up first. And, here’s the study.

The hydrolyzed formula did seem to reduce the appearance of at least one autoimmune antibody—but not two or more, which is more predictive of the development of the disease. But, that was enough for the investigators to embark on the “ambitious” TRIGR study, the “Trial to Reduce Incidence of Diabetes in Genetically at Risk, a multinational, randomized prospective trial” involving randomizing thousands of newborns across 15 countries, with expected completion in 2017. But, in 2010, we got some preliminary data suggesting it may have helped, but didn’t quite reach statistical significance—meaning, basically, there was a greater than 1 in 20 chance it could have just been a fluke. And, indeed, when the autoimmune antibody results were published after 7 years of follow-up, the special hydrolyzed formula didn’t seem to help at all.

Now, they did just look at a special group of children at high genetic risk, with diabetes running in the family, whereas the great majority of children who get type 1 diabetes don’t have any afflicted close relative. But, perhaps most importantly, 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—just what effect the hydrolyzed casein formula might have.

Maybe it’s not the casein; 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, [cow insulin, around the same time the other researchers were looking into casein, this research team was following] 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 only have been exposed to a few cow proteins through their mom’s breast milk, if their mom drank the stuff.

Furthermore, the “bovine…antibodies…cross-reacted [to] human insulin,” potentially being that caught-in-the-crossfire cause that triggers at least some cases of type 1 diabetes, but you can’t know for sure, until (you guessed it!) you put it to the test.

Same as the other one, a randomized, double-blind trial. But, this time, they 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. But, what we don’t yet know is if this will translate into fewer cases of diabetes. Stay tuned.

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