I remain intrigued about Vitamin D and its relationship to diabetes, obesity, and overall health. As I have written in past blogs, there appears to be a correlation with sunlight exposure (and Vitamin D levels) with the development of Type 1 diabetes. Countries furthest away from the equator appear to have higher incidences of type 1 diabetes. Once again, this information does not prove that low Vitamin D levels cause diabetes, however, there seems to be some relationship between metabolism and Vitamin D.
In the paper, “Correcting Vitamin D insufficiency improves insulin sensitivity in obese adolescents: a randomized controlled trial” (The American Journal of Clinical Nutrition, doi: 10.3945/ajcn.112.050013), Belenchia, Tosh, Hillman, and Peterson once again discuss Vitamin D and its relationship to insulin. According to the authors, obese adolescents appear to be at greater risk of Vitamin D deficiency due to the hypothesis that Vitamin D is stored by excess fat tissue. As I stated above, the authors noted that low Vitamin D levels are associated with metabolic syndrome and type 2 diabetes in both adolescents and adults.
The goal of the study was to determine the “efficacy and safety of 4,000 IU Vitamin D3 and if subsequent increased circulating concentrations of 25-hydroxyvitamin D (common lab measurement for Vitamin D levels) are associated with improved markers of insulin sensitivity and resistance and reduced inflammation.”
Who were the subjects?
- 35 obese adolescents with an average age of 14 with a BMI of 39.8 and a 25-hydroxyvitamin D level of 19.6+/-7.1 ng/mL were recruited from The University of Missouri’s Adolescent Diabetes and Obesity Clinic.
- The 35 adolescents were randomly assigned to receive Vitamin D3 at 4,000 IU/dose OR placebo.
- Measurements of various metabolic components including inflammatory markers, fasting blood sugars, and anthropometric features were obtained at baseline and at 3-month and 6-month follow-up visits.
What were the results?
- After 6 months, there were no significant differences in BMI, serum inflammatory markers, or plasma glucose levels between groups.
- Subjects supplemented with Vitamin D3 as compared to those with placebo had:
- Increases of 25 hydroxyvitamin D levels of 19.5 ng/mL and 2.8 ng/mL respectively (p<0.001).
- Fasting insulin levels (-6.5 uU/mL and +1.2 uU/mL respectively (p=0.026).
- Inflammatory markers remained unchanged.
The authors conclude that correction of poor Vitamin D status through dietary supplementation of Vitamin D may help in the treatment of obesity and associated insulin resistance. According to Dr. Peterson, “by increasing Vitamin D intake alone, we got a response that was nearly as powerful as what has been seen using a prescription drug.”
What is the practical implication of this paper?
I have been checking hydroxyvitamin D levels in many of my patients due to my interest in the association of Vitamin D and diabetes. In many cases, I have found them to be low, especially in my obese patients with type 1 and type 2 diabetes. I have been supplementing with vitamin D3 in an effort to increase levels to greater than or equal to 30 ng/mL. Anecdotally, I have yet to note any significant changes in insulin sensitivity in terms of insulin doses. I will continue to supplement in view of the lack of harm to patients and the unknown benefit that might result from the Vitamin D administration.