Vitamin D Studies on Serum Samples

Some publications suggest that vitamin D levels of Finnish children are lower than recommended. There have even been speculations that this might be linked to the high occurrence of type 1 diabetes (T1D) in the Finnish population.

We are now studying whether serum vitamin D levels differ between children who have developed T1D, children who are healthy but have T1D related autoantibodies, and a selected group of control children who remain autoantibody negative. A similar study will be made using serum samples from children diagnosed with celiac disease (CD), children with CD related autoantibodies, and matched autoantibody-negative control children. We are also conducting a general survey of serum vitamin D levels in children participating in the DIPP study; we also study how these levels fluctuate during different seasons and different years. The main source of vitamin D is the UV-light from the sun. Consequently serum vitamin D levels peak towards the end of the summer. Vitamin D has also been added to milk products in Finland since 2003 and this, in part, causes differences in the samples taken during different years.

Two forms of vitamin D are measured from the serum samples selected for this study. The storage form of vitamin D, also called 25-hydroxy-vitamin D, or calcidiol, is measured from most of the samples, but from some also the amount of the active form called 1,25-hydroxy-vitamin D or calcitriol is measured. No action is required from the DIPP study families to participate in the vitamin D studies.