1 Paediatric and International Nutrition, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet2 National Institute of Public Health, University of Southern Denmark3 Steno Diabetes Center, Gentofte4 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet5 Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark.6 Department of Public Health, Aarhus University, Aarhus7 Department of Clinical Biochemistry and Immunology, Statens Serum Institut, Copenhagen8 Greenland Centre for Health Research, University of Greenland, Nuuk9 Paediatric and International Nutrition, Department of Nutrition, Exercise and Sports, Faculty of Science, Københavns Universitet10 Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet
BACKGROUND: Low vitamin D status may be pronounced in Arctic populations due to limited sun exposure and decreasing intake of traditional food. OBJECTIVE: To investigate serum 25(OH)D3 as a measure of vitamin D status among adult Inuit in Greenland, predictors of low serum 25(OH)D3 concentrations and the trend from 1987 to 2005-2010. DESIGN: A total of 2877 randomly selected Inuit (≥18 years) from the Inuit Health in Transition study were included. A sub-sample (n = 330) donated a blood sample in 1987 which allowed assessment of time trends in vitamin D status. RESULTS: The geometric mean serum 25(OH)D3 (25[OH]D2 concentrations were negligible and not reported) in 2005-2010 was lowest among the 18-29 year old individuals (30.7 nmol/L; 95% CI: 29.7; 31.7) and increased with age. In all age-groups it decreased from 1987 to 2005-2010 (32%-58%). Low 25(OH)D3 concentrations (<50 nmol/L) were present in 77% of the 18-29 year old and decreased with age. A characteristic seasonal variation in 25(OH)D3 concentrations was observed (range 33.2-57.1 nmol/L, p<0.001), with the highest concentrations in August to October. Age (2.0% per year increase; CI: 1.7, 2.2), female gender (7.1%; CI: 2.0; 12.5), alcohol intake (0.2% per increase in drinks/week; 0.0; 0.4), and traditional diet (10.0% per 100 g/d increase; CI: 7.9; 12.1) were associated with increased serum 25(OH)D3, whereas smoking (-11.6%; CI: -16.2; -6.9), BMI (-0.6%; CI: -1.1; -0.2) and latitude (-0.7% per degree increase; CI: -1.3; -0.2) were associated with decreased concentrations. CONCLUSION: We identified a remarkable decrease in vitamin D status from 1987 to 2005-2010 and a presently low vitamin D status among Inuit in Greenland. A change away from a traditional diet may well explain the observed decline. The study argues for the need of increased dietary intake of vitamin D and supplementation might be considered.