To assess vitamin D status and the impact of three fish meals consisting of cod liver and fresh cod-liver oil on the plasma level of vitamin D metabolites in an area with high consumption of cod liver and cod-liver oil.

Experimental field study.

Thirty-two volunteers from the Skjervøy (70°N) municipality in northern Norway were recruited to consume three traditional mølje meals, consisting of cod, cod liver, fresh cod-liver oil and hard roe, in one week. The liver and fresh cod-liver oil consumed by the participants were weighed and recorded. Blood samples were collected before the first meal, and subsequently 12h and 4 days after the last meal. The blood samples were analysed for the vitamin D metabolites 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D). All participants answered a semi-quantitative food-frequency questionnaire, which was used to estimate usual daily nutrient intake. The study was carried out in the last part of March 2001.

The median daily vitamin D intake estimated from the questionnaire was 9.9μg. The proportion of subjects with baseline 25(OH)D level below 50nmoll−1 was 15.4% and none were below 37.5nmoll−1. Only ‘mølje consumption’ and ‘time spent in daylight’ were significantly associated with baseline log 25(OH)D. The mean total intake of vitamin D in the three servings was 272μg (standard deviation 94μg), ranging from 142 to 434μg. Relative to baseline plasma concentration, the mean level of 25(OH)D decreased slightly in both post-consumption samples (P≤0.03), while 1,25(OH)2D peaked 12h after the final meal (P = 0.03).

Three mølje meals provided, on average, an amount of vitamin D equal to 54 times the recommended daily dose. Subjects with food consumption habits that included frequent mølje meals during the winter sustained satisfactory vitamin D levels in their blood, in spite of the long ‘vitamin D winter’ (i.e. absence of ultraviolet-induced vitamin D production in the skin).

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.

Cross-sectional study.

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.

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.

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.