ABSTRACT
A prospective, nonblinded and nonrandomized controlled trial was conducted to test the hypothesis that vitamin D supplementation would improve glycemic control in patients with type 1 diabetes mellitus who have vitamin D deficiency. Eight patients with type 1 diabetes mellitus who had 25-hydroxyvitamin D levels less than 50 nmol/L were assigned to receive 4000 IU of vitamin D3. Calcium supplements were provided to ensure a total calcium intake of 1200 mg/d. Glycosylated hemoglobin and 25-hydroxyvitamin D levels were measured at baseline and at 12 weeks. There was a significant difference in mean [SD] glycosylated hemoglobin level [%] between the groups that achieved 25-hydroxyvitamin D levels of <35.4 nmol/L, 35.4-51 nmol/L and >51 nmol/L at 12 weeks [P=.02]. There was a significant difference in glycosylated hemoglobin change from baseline between the groups that achieved 25-hydroxvitamin D levels of<35.4 nmol/L, 35.4-51 nmol/L and >51 nmol/L at 12 weeks [P=0.4]. There was a significant difference in25-hydroxyvitamin D level between the groups that achieved glycosylated hemoglobin levels of <7.8, 7.8-9.9 and >9.9 at 12 weeks [P=.001]. Patients were more likely to achieve lower glycosylated hemoglobin levels at 12 weeks if they had higher 25-hydroxyvitamin D levels at 12 weeks [r=-0.4, p=0.01]. There was an observed effect of vitamin D supplementation on glycemic control in vitamin D-replete, type 1 diabetes mellitus patients. Further studies are needed to determine if these findings are applicable