Type 1 diabetes has a pretty well defined genetic component, but also an ill defined (that is, not understood) environmental component. From studies in identical twins, we know that genetics alone are not enough. When one identical twin has type 1, the other has only a 50% risk -- not 100% if type 1 were purely genetic. The environment factor (or factors) is not known, in spite of many theories that have included early exposure to cow's milk and vaccinations, neither of which have stood up to scrutiny (in spite of what some may say). There is some thinking that early exposure to wheat may be a trigger, and that is under study right now.