title: Vitamin D status in North Greenland is influenced by diet and season: indicators of dermal 25-hydroxy vitamin D production north of the Arctic Circle.
abstract: Vitamin D status, as measured by serum 25-hydroxy vitamin D (s-25OHD), is important to human health. Dermal 25OHD production depends on UVB light that is influenced by latitude. We aimed to identify factors important to the production of s-25OHD in Arctic people and investigated subjects living in the town of Ilulissat and the settlement of Saqqaq in North Greenland (70°N) during the four seasons. Participants were enrolled with a balanced representation of non-Inuit and Inuit in Ilulissat and Inuit in Saqqaq, men and women, aged 30-39 and 40-49 years. Supplement use, hours spent outdoors and other lifestyle factors were determined by questionnaires. Scores of traditional Inuit food intake were computed from a FFQ at inclusion, and frequencies of intake were recorded at each visit. s-25OHD concentration was measured. There were sixty-four Inuit and thirty-three non-Inuit participants. Inuit food score < 40 % was found in 87, 64 and 48 % of non-Inuit, Inuit in Ilulissat and Inuit in Saqqaq participants, respectively (P= 0·009). Inuit diet associated positively with s-25OHD (P< 0·001). s-25OHD concentration was lower in non-Inuit than in Inuit participants (spring/summer/autumn/winter/average: 30·3 v. 36·8/43·2 v. 44·7/43·6 v. 48·6/32·8 v. 43·5/39·0 v. 44·6 nmol/l, P= 0·002/0·62/0·19/ < 0·001/0·011, respectively). s-25OHD levels differed with season (Inuit, P< 0·001; non-Inuit, P< 0·001) as did diet (Inuit, P< 0·001; non-Inuit, P< 0·001) and hours spent outdoors (Inuit, P< 0·001; non-Inuit, P= 0·012). s-25OHD level was influenced by diet (P< 0·001), season (P< 0·001), origin (P= 0·001), residence (P= 0·013) and sex (P= 0·026). We conclude that the season influenced vitamin D status in Arctic populations beyond diet, ethnicity and vitamin intake. This suggests dermal 25OHD production at a high latitude of 70°N.
authors.affiliation: Arctic Health Research Centre, Aalborg University Hospital, Hobrovej 42D-1, 9000 Aalborg, Denmark. stiga@dadlnet.dk
authors.forename: Stig
authors.initials: S
authors.lastname: Andersen
authors.forename: Anna
authors.initials: A
authors.lastname: Jakobsen
authors.forename: Peter
authors.initials: P
authors.lastname: Laurberg
mesh_terms: D000328:Adult; D001110:Arctic Regions / Q000208:ethnology; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006116:Greenland / Q000208:ethnology; D006304:Health Status; D006801:Humans; D004930:Inuit; D008019:Life Style; D008297:Male; D008875:Middle Aged; D012621:Seasons; D012737:Sex Factors; D012867:Skin / Q000378:metabolism*; D013472:Sunlight; D011795:Surveys and Questionnaires; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000097:blood* / Q000208:ethnology
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D