More and more research is being done on the link between Vitamin D deficiency and the rise in auto-immune disorders like Type 1. Dan Hurley's book, Diabetes Rising, calls this the "sunshine hypothesis." This hypothesis states that since we now spend more time in doors, we are getting less sun and thus reducing the amount of Vitamin D that we are taking in. Likewise, when we are out-of-doors, we often use sunscreen, which further inhibits our intake of Vitamin D.
This deficiency has been noted by the American Academy of Pediatrics, who, in 2009, recommended an increase of 200 IUs to 400IUs per day for infants, children, and adolescents. If Vitamin D is not something that you are monitoring with your kids, you might want to consider working with your pediatrician, family doctor, or endocrinologist to do so.