Vitamin D status in a rural population of northern Norway with high fish liver consumption

Abstract

AbstractObjective: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.Design:Experimental field study.Methods: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.Results: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).Conclusion: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).