I can buy trying to figure out allergies, but Type I diabetes? It's clearly hereditary, rarely showing up without some family link. Finland may have a high rate due to a lack of ethnic diversity.
Hereditary, but not in a strong sense - to quote the american diabetes association:
> In general, if you are a man with type 1 diabetes, the odds of your child getting diabetes are 1 in 17. If you are a woman with type 1 diabetes and your child was born before you were 25, your child's risk is 1 in 25; if your child was born after you turned 25, your child's risk is 1 in 100.
Even if both partners are diabetic, the risk is only 1 in 10 to 1 in 4. This strongly implies that what is heritable is the vulnerability to getting diabetes, rather than getting diabetes itself. There is, presumably, some trigger that also needs to occur.
Clearly? Identical twins do not have the same likeliness of developing T1DM. Genetics do not explain why we have had a significant global growth (~3% per year) in the number of cases of Type 1 Diabetes Melanoma (T1DM) in recent decades. There are even a number of vaccines in development (with early successes).
In many cases a T1DM diagnosed child was sick with a cold/flu immediately prior to onset of T1DM. Disease has been theorized for quite a long time to influence the immune system's reaction. A large majority of T1DM cases are diagnosed in winter, Vitamin D / sunlight has been hypothesized to play a role - more northern countries tend to have higher rates.
Even in the hereditary factor, here is research indicating that epigenetics play a role - timing of food shortages during our grandparents' lives significantly increases likeliness of T1DM. That appears to be an environmental factor tweaking our genes.
