Vitamin D insufficiency in Aboriginal Australians

Abstract

Objective: To investigate the adequacy of vitamin D status in a South Australian Aboriginal population, and to examine the relationship between serum 25-hydroxyvitamin D (25-OHD) levels and biochemical variables of calcium and bone mineral homeostasis, as well as other factors which may influence vitamin D synthesis, storage and metabolism. Design, setting and participants: A single-visit, observational study of 58 adults from two Aboriginal community-controlled health services in Adelaide and Yalata, South Australia. Participants were recruited between May 2008 and December 2009. Main outcome measures: Serum levels of 25-OHD, parathyroid hormone (PTH), fasting glucose and fasting C-terminal telopeptides of type I collagen (β-CTx). Results: Serum 25-OHD levels showed clear seasonal variation, being higher in summer (P < 0.001). The overall mean level was 56.8 nmol/L (SD, 22.1), which is below the recommended target level of 60 nmol/L. Serum 25-OHD levels correlated significantly with β-CTx (P = 0.03), but not with age, body mass index (BMI), PTH levels or levels of fasting glucose. A significant association was found between BMI and PTH levels (P = 0.001). A significant inverse association between serum 25-OHD levels and BMI, observed in other studies, was not found in our study. Conclusions: Vitamin D insufficiency is highly prevalent in this population of adult Aboriginal Australians, with low mean values found in all seasons other than summer.