Older age and lower adiposity predict better 25-hydroxy vitamin D concentration in Inuit adults: International Polar Year Inuit Health Survey, 2007–2008

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Our aim was to determine the prevalence and correlates of serum 25-hydroxy vitamin D (25(OH)D) concentration in Inuit adults. Low 25(OH)D concentration (< 50 nmol/L) was common; the strongest positive predictors were older age and healthy waist circumference. Nutritional health promotion and interventions along with longitudinal nutritional assessments are needed. While 25(OH)D concentration of Canadian Inuit has not been examined on a large scale, Nutrition Canada Survey (1973) suggested that Inuit have low intakes of vitamin D. Our main purpose was to determine the prevalence and correlates of 25(OH)D concentration in a recent Inuit Health Survey. Inuit adults (≥ 18 years) participated in the 2007-2008 International Polar Year Inuit Health Survey conducted in the months of August to October. Households were selected randomly in 36 communities. Dietary intake was assessed using a 24-h recall and a food frequency questionnaire. Anthropometric measurements, household living conditions, supplement use, and health status were assessed. In fasting samples, serum 25(OH)D and parathyroid hormone were measured using chemiluminesent assays (Diasorin, Liaison). Of the 2,595 participants, serum 25(OH)D was available on 2,207, of whom 67.4% and 42.2% had concentrations below 75 and 50 nmol/L, respectively. Further, 27.2% had values <37.5 nmol/L. Older adults (≥ 51 years) consumed higher quantities of traditional food and consequently had higher vitamin D intake than younger adults (18-30 and 31-50 years) (p < 0.05). The strongest positive predictors of 25(OH)D (≥ 50 or 75 nmol/L) among Inuit adults were older age and healthy waist circumference. This is the first population assessment of dietary vitamin D and 25(OH)D concentration in Inuit adults. The high prevalence of suboptimal 25(OH)D concentration noted in the late summer and early fall raises concerns of greater prevalence and more severe inadequacies in the winter.