Correcting vitamin D insufficiency improves insulin sensitivity in obese adolescents: a randomized controlled trial.
Am J Clin Nutr. 2013 Feb 13.
Belenchia AM, Tosh AK, Hillman LS, Peterson CA.
Department of Nutrition and Exercise Physiology, University of Missouri, Columbia, MO.
BACKGROUND: Obese adolescents are at a greater risk of vitamin D deficiency because vitamin D is thought to be sequestered by excess adipose tissue. Poor vitamin D status has been associated with a higher prevalence of the metabolic syndrome, type 2 diabetes, or both in adults and adolescents.
Objective: The objective was to determine in obese adolescents the efficacy and safety of 4000 IU vitamin D(3)/d and whether subsequent increased circulating concentrations of 25-hydroxyvitamin D [25(OH)D] are associated with improved markers of insulin sensitivity and resistance and reduced inflammation.
DESIGN: Obese adolescent patients [n = 35; mean ± SD age: 14.1 ± 2.8 y; BMI (in kg/m(2)): 39.8 ± 6.1; 25(OH)D: 19.6 ± 7.1 ng/mL] were recruited from the University of Missouri Adolescent Diabetes and Obesity Clinic and were randomly assigned to receive either vitamin D(3) (4000 IU/d) or placebo as part of their standard care. Anthropometric measurements, inflammatory markers (IL-6, TNF-α, C-reactive protein), adipokines (leptin, adiponectin), fasting glucose, fasting insulin, and HOMA-IR values were measured at baseline and at 2 follow-up visits (3 and 6 mo).
Results: After 6 mo, there were no significant differences in BMI, serum inflammatory markers, or plasma glucose concentrations between groups.
Participants supplemented with vitamin D(3) had increases in
- serum 25(OH)D concentrations (19.5 compared with 2.8 ng/mL for placebo; P < 0.001),
- fasting insulin (-6.5 compared with +1.2 μU/mL for placebo; P = 0.026),
- HOMA-IR (-1.363 compared with +0.27 for placebo; P = 0.033), and
- Leptin-to-adiponectin ratio (-1.41 compared with +0.10 for placebo; P = 0.045).
Inflammatory markers remained unchanged.
Conclusion: The correction of poor vitamin D status through dietary supplementation may be an effective addition to the standard treatment of obesity and its associated insulin resistance. This trial was registered at clinicaltrials.gov as NCT00994396.