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Treating Vitamin D Deficiency In Children With Type 1 Improves Glycemic Control

Use of cholecalciferol demonstrated reductions in HbA1c.

The active form of vitamin D is a very important hormone that works in the body by increasing the absorption of calcium. Vitamin D deficiency has been implicated in a variety of chronic diseases, including bone mineral disease, malignancy, autoimmunity, and diabetes. In recent years, it has been found that beta cells express the vitamin D receptor (VDR) and variations in the genes controlling the vitamin D metabolism and expression of VDR have been associated with a higher risk of diabetes, including type 1 and type 2. Patients with serum concentration of vitamin D below 30 nmol/L and 30-50 nmol/L are categorized as deficient and insufficient, respectively.  Daily supplementation of vitamin D in the diet and sunlight exposure in the diet is essential for preventing deficient levels.

Some studies have associated vitamin D deficiency with beta cell dysfunction and insulin resistance with a consequent development of type 2 diabetes in the adult population. In children with type I diabetes mellitus (T1DM), the prevalence of vitamin D deficiency has been found to be higher when compared to children without diabetes. Other studies have found the prevalence of vitamin D deficiency is similar between children with and without diabetes. Furthermore, a Finnish study reported that there was a 4-fold increased risk of development of T1DM in children who had rickets, which is a long-term effect of vitamin D deficiency causing weak bones. All these background studies suggest that there is a possible correlation between vitamin D deficiency and the risk of both type 1 and 2 diabetes. However, there is poor evidence related to the effects of vitamin D treatment in children with diabetes and vitamin D deficiency.

A retrospective study accessed medical records of a total of 271 children and teens with T1D attending outpatient diabetes clinics. All of them were screened for 25 (OH) levels and classified as deficient, insufficient, or optimal. Children classified as deficient received 6000 U of cholecalciferol for 3 months. Children with vitamin D deficiency were treated with 400 U of cholecalciferol for 3 months. They also had their HbA1c checked before and after the completion of treatment and plasma 25(OH)D concentration was measured after the completion of treatment.

From the total number of participants, 40 (14.8%) had vitamin D deficiency and 84 (31.0%) of the children were vitamin D insufficient; 147 (54.2%) children had normal serum concentrations of 25(OH)D (>50 nmol/l) and therefore were classified as optimal and were excluded from future observations. Of the remaining 124, only 73 of them included a HbA1C baseline and were therefore analyzed for association with T1D.

Using a multiple regression analysis, it was found that children with a higher HbA1c (6000 U) before treatment had a significantly greater reduction in HbA1c (p < 0.001) after treatment with cholecalciferol. The children with lower vitamin D levels showed a significantly higher reduction in HbA1c (p = 0.004) after treatment with cholecalciferol.

This study found a significant improvement in the glucose levels (measured by HbA1c) upon treating the vitamin D deficiency in children and adolescents with T1D. It was shown that the glycemic control notably improves with normalization of vitamin D concentrations. Furthermore, it was shown that the group of children with the highest blood glucose levels and those with the lowest 25(OH)D levels demonstrated a higher improvement in their HbA1c after treatment with cholecalciferol.

This study, despite its limitations due to its retrospective nature, supports the principle of vitamin D assessment and optimization in children with type 1 diabetes. Therefore, it is important to note that vitamin D deficiency is common in diabetes and treatment of the same may help improve glycemic control. Future prospective randomized trials will be crucial to understand the long-term effects of vitamin D supplementation on children and adolescents with TIDM and their glycemic profiles.

Practical Pearls:

  • Vitamin D deficiency is common in children and teenagers with type 1 diabetes.
  • Optimal vitamin D levels may improve glycemic control.
  • Treatment with cholecalciferol has demonstrated reductions in HbA1c in children with vitamin D deficiency.


Chiu KC, Chu A, Go VL, Saad MF. Hypovitaminosis D is associated with insulin resistance and beta cell dysfunction. Am J Clin Nutr. 2004; 79:820–825.

Hyppönen E, Läärä E, Reunanen A, Järvelin MR, Virtanen SM. Intake of vitamin D and risk of type 1 diabetes: a birth-cohort study. Lancet. 2001; 358:1500–1503.

Dinesh Giri, Dona Pintus. Treating vitamin D deficiency in children with type I diabetes could improve their glycaemic control. BMC Res Notes. 2017; 10: 465.

Fabio Rodriguez, PharmD. candidate 2018, LECOM School of Pharmacy