a1 Institute of Community Medicine, University of Tromsø, N-9037 Tromsø, Norway
a2 Norwegian Institute for Air Research, The Polar Environmental Centre, Tromsø, Norway
a3 Department of Paediatrics, University of Bergen, Bergen, Norway
Objective: To determine the vitamin D status of middle-aged women living in the Norwegian arctic and its relationship with vitamin D intake and exposure to ultraviolet (UV) radiation.
Design: Cross-sectional study.
Subjects and setting: This study is based on measurements of 25-hydroxyvitamin D (25(OH)D) levels in a sub-sample of the Norwegian component of the EPIC biological bank, which consists of blood samples from a random selection of participants in the Norwegian Women and Cancer Study. From November 2001 until June 2002, 309 blood samples were collected from a total of 443 invited middle-aged women (44–59 years) in northern Norway (65–71°N) (crude response rate, 69.8%). Questionnaire data provided information on dietary sources of vitamin D and UV exposure.
Results: Median plasma 25(OH)D concentration for the whole group was 55.0 nmol l−1 (range 8.1–142.8 nmol l−1). Vitamin D intake was a significant predictor of 25(OH)D status (P = 0.0003). The time of the year when the blood sample was collected significantly predicted plasma 25(OH)D level (P = 0.005). Levels of 25(OH)D were positively associated (P = 0.0002) with estimated hours per day of exposure to UV-B radiation. Residing in northern Norway during the summer prior to blood sampling was negatively associated with 25(OH)D concentration (P = 0.001). The prevalence of moderate hypovitaminosis D was highest in January–February, when a quarter of the participants had 25(OH)D concentrations ≤37.5 nmol l−1.
Conclusions: Increased ingestion of marine food items that provide vitamin D should be promoted and further studies should be carried out to investigate vitamin D status in arctic populations in relation to both UV exposure and traditional food sources.
(Received June 09 2003)
(Accepted September 03 2003)