Researchers have shown that mice exposed to common stomach bacteria are protected against the development of type 1 diabetes. The findings support the “probiotics theory” (the theory that bacteria does good things for health) and "hygiene hypothesis" (the theory that lack of exposure to parasites and bacteria in our sterile lives may lead to increased risk of diseases).
In Type I diabetes, it was found that patients given common stomach bacteria, such as occur in raw milk, patient's pancreatic cells that produce insulin were reconstructed and regenerated. This proves that exposure to some forms of bacteria will help prevent onset of Type 1 diabetes as well as reverse it. Hippocrates and Dr. Crewe both proved that an all raw milk diet alone reverses diabetes Types 1 and 2.

Sources:
Science Daily September 21, 2008 and Nature September 28, 2008.