**12. Vitamin D and type 1 diabetes**

Experimental studies suggest that vitamin D may play a role in the defence against type 1 diabetes as well as type 2 diabetes. Epidemiological data suggest that there is a link between vitamin D deficiency and an increased incidence of Type 1 diabetes. A multinational casecontrol study and a birth cohort follow-up study from Finland [86] have concluded that vita‐ min D3 supplementation at birth protects against type 1 diabetes later in life, and a metaanalysis supports similar conclusions [87]. Low serum levels of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3, calcitriol] has been found in patients with recently diagnosed type 1 diabetes. The protective effects of vitamin D against diabetes are mediated through the regulation of several components such as the immune system and calcium homeostasis. Thus, mechanistic studies show that 1,25(OH)2D3 modulates dendritic cell maturationand facilitates a shift from a Th1 to a Th2 immune response. There is also ncreasingevidence suggesting that vitamin D also affects beta cells directly thereby rendering them more resistant to cellular stress. There are results indicating that Vitamin D may also improve insulin sensitivity, which in turn de‐ crease beta cell stress.

Vitamin D has been used in patients with recent onset Type 1 diabetes in an effort to preserve residual insulin secretion. However, so far Vitamin D alone has not been efficacious [88. 89]. It seems resaonable to try Vitamin D, both in higher dose, and in combination with other therapy.
