Baseline serum 25-hydroxy vitamin D is predictive of future glycaemic status and insulin resistance: The MRC Ely prospective study 1990 – 2000

Abstract

Objective: Accumulating epidemiological evidence suggests that hypovitaminosis D may be associated with type 2 diabetes and related metabolic risks. However, prospective data using the biomarker serum 25-hydroxyvitamin D (25(OH)D) are limited and therefore examined in the present study.

Research Design and Methods: 524 randomly selected non-diabetic men and women aged 40-69 years at baseline with measurements for serum 25(OH)D and insulin-like growth factor-1 (IGF-1) in the population-based Ely Study had glycaemic status (oral glucose tolerance), lipids, insulin, anthropometry and blood pressure measured, and metabolic syndrome risk score (MS-z) derived at baseline and at 10-years of follow-up.

Results: Age-adjusted baseline mean serum 25(OH)D was greater in men (64.5 (95% CI 61.2-67.9) nmol/L) than women (57.2 (54.4,60.0) nmol/L) and varied with season (highest late summer). Baseline 25(OH)D was associated inversely with 10-year risk of hyperglycemia (fasting glucose: beta -0.0023, p=0.019; 2h-glucose: beta -0.0097, p=0.006), insulin resistance (fasting insulin beta -0.1467, p=0.010; HOMA-IR: beta -0.0059, p=0.005) and MS-z score (beta -0.0016, p=0.048) after adjustment for age, sex, smoking, BMI, season and baseline value of each metabolic outcome variable. Associations with 2h-glucose, insulin and HOMA-IR remained significant after further adjustment for IGF-1, parathyroid hormone, calcium, physical activity and social class.

Conclusions: This prospective study reports inverse associations between baseline serum 25(OH)D and future glycemia and insulin resistance. These associations are potentially important in understanding the etiology of abnormal glucose metabolism, and warrant investigation in larger specifically designed prospective studies and randomized controlled trials of supplementation.