Type 1 Diabetes: No Vitamin D-Glycemic Control Link

There was no significant relationship between glycemic control and vitamin D levels among children and adolescents with type 1 diabetes, according to a new observational study.

Researchers analyzed nearly 200 children and found that 40.6% of them had what is considered deficient 25-hydroxyvitamin D levels of ≤50 nmol/L; 49.2% of them had insufficient levels from 51 and 75 nmol/L, and 10.2% of them had a normal level of >75 nmol/L. But the relationship between HbA1c levels and vitamin D levels was not significant (P=0.057), according to co-author Terri Lipman, PhD, at the University of Pennsylvania school of nursing.

Lipman and colleagues published their findings in Diabetes Research and Clinical Practice.

"Although the benefit of normal 25-hydroxyvitamin D levels in type 1 diabetes is yet to be established, the negative effects of vitamin D deficiency have been demonstrated," wrote the authors. "This data emphasize the importance of screening 25-hydroxyvitamin D levels in all youth with type 1 diabetes."

Previous studies have indicated that low vitamin D levels are a significant risk factor for worsened glucose control and type 1 diabetes, wrote the authors. But many studies looking at the link were longitudinal and weren't ideally powered to determine that relationship.

All participants were 7-18 years old and had type 1 diabetes for at least 1 year. Data were drawn from the Diabetes Center for Children at the Children's Hospital of Philadelphia. Patients who had a history of smoking, HbA1c levels of >12%, a history of ketoacidosis episodes, inflammatory disorders, or other relevant disorders were excluded. Data on socioeconomic status, weight, age, sex, and type 1 diabetes management was collected.

The mean age of the participants was 13, and most were males (57%), white (55%, and had private insurance (70%). About 23% were overweight and 13% were obese; 36% were being treated with insulin pump therapy and the rest were on regiments of multiple insulin injections. The mean Hba1c level was 8.6, wrote Lipman and colleagues.

Ethnicity, insurance status, duration of diabetes, and the type of insulin regimen were all significantly associated with HbA1c.

Limitations of the study include its cross-sectional design, so researchers cold not determine causal relationships. In addition, the sample size was relatively small, and data on sun exposure of the children and adolescents was not collected.

"A future trial studying the impact of vitamin D supplementation on glycemic control for children with type 1 diabetes who have low 25-hydroxyvitamin D levels is indicated," concluded the authors.

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