Vitamin D Supplementation Does Not Impact Insulin Resistance in Black and White Children

J Clin Endocrinol Metab. 2016 Apr;101(4):1710-8. doi: 10.1210/jc.2015-3687. Epub 2016 Feb 17.

Abstract

Context: Vitamin D supplementation trials with diabetes-related outcomes have been conducted almost exclusively in adults and provide equivocal findings.

Objective: The objective of this study was to determine the dose-response of vitamin D supplementation on fasting glucose, insulin, and a surrogate measure of insulin resistance in white and black children aged 9–13 years, who participated in the Georgia, Purdue, and Indiana University (or GAPI) trial: a 12-week multisite, randomized, triple-masked, dose-response, placebo-controlled vitamin D trial.

Design: Black and white children in the early stages of puberty (N = 323, 50% male, 51% black) were equally randomized to receive vitamin D3 (0, 400, 1000, 2000, or 4000 IU/day) for 12 weeks. Fasting serum 25-hydroxyvitamin D (25(OH)D), glucose and insulin were assessed at baseline and weeks 6 and 12. Homeostasis model assessment of insulin resistance was used as a surrogate measure of insulin resistance. Statistical analyses were conducted as intent-to-treat using a mixed effects model.

Results: Baseline serum 25(OH)D was inversely associated with insulin (r = −0.140, P = 0.017) and homeostasis model assessment of insulin resistance (r = −0.146, P = 0.012) after adjusting for race, sex, age, pubertal maturation, fat mass, and body mass index. Glucose, insulin, and insulin resistance increased (F > 5.79, P < .003) over the 12 weeks, despite vitamin D dose-dependent increases in serum 25(OH)D.

Conclusions: Despite significant baseline inverse relationships between serum 25(OH)D and measures of insulin resistance, vitamin D supplementation had no impact on fasting glucose, insulin, or a surrogate measure of insulin resistance over 12 weeks in apparently healthy children.

Trial registration: ClinicalTrials.gov NCT00931580.

MeSH terms

  • Adolescent
  • African Continental Ancestry Group
  • Blood Glucose*
  • Body Composition / physiology
  • Child
  • Cholecalciferol / administration & dosage*
  • Dietary Supplements*
  • Dose-Response Relationship, Drug
  • European Continental Ancestry Group
  • Fasting / blood
  • Female
  • Humans
  • Insulin / blood*
  • Insulin Resistance / physiology*
  • Male
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood

Substances

  • Blood Glucose
  • Insulin
  • Vitamin D
  • Cholecalciferol
  • 25-hydroxyvitamin D

Associated data

  • ClinicalTrials.gov/NCT00931580