Reduction in vitamin D levels has been reported in subjects with recent onset type 1 diabetes. Several studies suggest that vitamin D supplementation in early childhood decreases the risk of developing type 1 diabetes, therefore vitamin D deficiency might play a role in the disease pathogenesis. We investigated whether the supplementation of the active form of vitamin D (calcitriol) in subjects with recent-onset type 1 diabetes can protect residual beta cell function evaluated by C peptide and improve glycaemic control as evaluated by HbA1c and insulin requirement.

Thirty-four subjects (age range 11-35 years, median 18 years) with recent-onset type 1 diabetes (<12 weeks duration) and high basal C-peptide >0.25 nmol/l were randomized in a double-blind trial to calcitriol (the active form of vitamin D, 1.25-dihydroxyvitamin D3 [1,25-(OH)2D3] ) at the dose of 0.25 ug/day or placebo, and followed up for 2 years.

Inclusion Criteria:

1. diagnosis of type 1 diabetes according to the American Diabetes Association (ADA) guidelines;
2. age at presentation between 11 and 35 years;
3. duration of clinical disease (since the beginning of insulin therapy) <12 weeks;
4. baseline C-peptide >0.25 nmol/l;
5. no medical contra-indications or any other major chronic disease;
6. willingness and capability to participate in a regular follow-up.

Exclusion Criteria:

1. cardiovascular disease;
2. renal disease;
3. liver disease;
4. neurological disorders;
5. allergic diathesis;
6. hyperparathyroidism;
7. neoplasia.