Associations between Vitamin D Status and Type 2 Diabetes Measures among Inuit in Greenland May Be Affected by Other Factors

PLoS One. 2016 Apr 13;11(4):e0152763. doi: 10.1371/journal.pone.0152763. eCollection 2016.

Abstract

Objective: Epidemiological studies have provided evidence of an association between vitamin D insufficiency and type 2 diabetes. Vitamin D levels have decreased among Inuit in Greenland, and type 2 diabetes is increasing. We hypothesized that the decline in vitamin D could have contributed to the increase in type 2 diabetes, and therefore investigated associations between serum 25(OH)D3 as a measure of vitamin D status and glucose homeostasis and glucose intolerance in an adult Inuit population.

Methods: 2877 Inuit (≥18 years) randomly selected for participation in the Inuit Health in Transition study were included. Fasting- and 2hour plasma glucose and insulin, C-peptide and HbA1c were measured, and associations with serum 25(OH)D3 were analysed using linear and logistic regression. A subsample of 330 individuals who also donated a blood sample in 1987, were furthermore included.

Results: After adjustment, increasing serum 25(OH)D3 (per 10 nmol/L) was associated with higher fasting plasma glucose (0.02 mmol/L, p = 0.004), 2hour plasma glucose (0.05 nmol/L, p = 0.002) and HbA1c (0.39%, p<0.001), and with lower beta-cell function (-1.00 mmol/L, p<0.001). Serum 25(OH)D3 was positively associated with impaired fasting glycaemia (OR: 1.08, p = 0.001), but not with IGT or type 2 diabetes.

Conclusions: Our results did not support an association between low vitamin D levels and risk of type 2 diabetes. Instead, we found weak positive associations between vitamin D levels and fasting- and 2hour plasma glucose levels, HbA1c and impaired fasting glycaemia, and a negative association with beta-cell function, underlining the need for determination of the causal relationship.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Blood Glucose / analysis
  • Diabetes Mellitus, Type 2 / blood*
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / etiology
  • Female
  • Glucose Intolerance / blood*
  • Glucose Intolerance / epidemiology
  • Glucose Intolerance / etiology
  • Glucose Tolerance Test
  • Greenland / epidemiology
  • Humans
  • Inuit
  • Male
  • Middle Aged
  • Prediabetic State / blood*
  • Prediabetic State / epidemiology
  • Prediabetic State / etiology
  • Risk Factors
  • Vitamin D / blood*
  • Vitamin D Deficiency / complications*
  • Vitamins / blood
  • Young Adult

Substances

  • Blood Glucose
  • Vitamins
  • Vitamin D

Grants and funding

The study was supported by the Government of Greenland’s health department (2011-047012/2012-074239), Aase and Ejnar Danielsen’s Foundation (10-000444), and Dagmar Marshalls Foundation. All grants were received by NON. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.