Back in 2006 when I was a newly diagnosed diabetic, I read a book by James McManus, Going to the Sun. It had come up in my university's library catalog when I looked for information on diabetes and travel, and it was a fiction book, a first person story by a woman whose blood sugar goes to 20 on a first date in one of the first scenes, which at the time seemed very unrealistic to me (a few months later when my own blood sugar starting dropping to the 20s without symptoms or warnings it stopped seeming unrealistic). The protagonist is angry at life and very resentful about diabetes- the shots and blood sugar checks and the long term health prognosis. At the end of the book, it seems that she commits suicide.
I learned a bit more about the book later. Talking to a librarian who ran a discussion group that had read the book, I learned that McManus is a local author- he lives within a few miles from me- and that the ending of the book is more ambiguous than I thought, and whether the protagonist does or doesn't commit the suicide she is contemplating at the end of the book was a hot topic in the book discussion. McManus has a daughter with type 1 diabetes- she was diagnosed at the age of 4 and went to the same children's hospital that I did, twenty-some years before me. I thought I'd be pretty upset about having a father who wrote a book with someone like me as the protagonist if that protagonist committed suicide at the end of the book, and wondered about the stories behind it.
So when I realized that James McManus had written a nonfiction book about American healthcare, Physical I thought I'd take a look and see if it helped me figure that out. I thought it was relevant that McManus's son- a euglycemic sort of guy- had died in a possible suicide. But it also seemed that he and his daughter do think of diabetes as being pretty horrid (not without reason- she developed proliferative retinopathy as a teenager) and they focus a lot on the downs of diabetes and hope for a cure (in embryonic stem cell research specifically).
But what was catching my attention was what McManus attributed his daughter's diabetes to. Twice he says that "her immune system suddenly attacked the islets of Langerhans in her pancreas, mistaking them for bovine serum albumin in cow milk protein." I thought that was a bit odd- was there any diabetogenic antibody that was known to attack bovine serum albumin?
Milk has been proposed as a trigger for type 1 diabetes, and in March 1989- right around the time McManus's daughter was diagnosed- a paper was published entitled "Could bovine serum albumin be the initiating antigen ultimately responsible for the development of insulin dependent diabetes mellitus?" This theory had been thought of as early as the 1960s and in the late 1980s and early 1990s gained steam.
Evidence exists. Children who were breastfed, rather than getting milk based formulas, have roughly two-thirds the risk of developing diabetes compared to those who were formula fed- a significant but not extreme reduction in risk. Some studies found higher rates of bovine serum antibodies in type 1 diabetics- other studies didn't. Even when slightly higher rates were found in type 1 diabetics, some people argued that this didn't prove that the antibodies caused diabetes. Type 1 diabetics, after all, are more likely to have thyroid antibodies as well- it's because we are more likely to have antibodies generally, not because thyroid antibodies cause diabetes. Milk protein antibodies at some level are present in about half of American adults, most of whom (obviously) do not have type 1 diabetes. Therefore, even those people who felt that BSA antibodies might be diabetogenic sometimes argued that testing for them was not worthwhile- because too many people have them. You can't guess somebody's diabetes status very accurately from the test. As markers for diabetes, they were deemed "neither sensitive nor specific", which is to say that many diabetics don't have them, and many non-diabetics do.
While the milk theory has not been thrown out, I think the evidence points to milk as a minor player in the cause of diabetes, and not as a soloist causing diabetes.
I myself did receive milk based formula as an infant in addition to breast milk, because my mother was working full time. I became a vegan at the age of eleven years but was a faithful milk drinker prior to that, and I think that whatever caused my diabetes had probably been set in motion well before I became vegan- my first diabetes symptoms showed up when I was thirteen.