I have read a number of anecdotal pieces that indicate that Vitamin D supplementation for infants and young children may reduce their chances of developing T1D.As a parent with T1D who would love to see his child miss this disease, the reports are interesting, however, the only study I’ve run across (and it has enough holes to be less than compelling) is here : http://pediatrics.jwatch.org/cgi/content/full/2008/423/1
I have not actually done any research on this but I did enroll my daughters in a trialnet study and since my youngest daughter had the autoantibodies, her doctor did his own research and prescribed her a specific kind of liquid vitamin D I give her in her mouth daily. There are also studies that indicate additional DHA is helpful to build the immune system and prevent the onset of Type 1.