The traditional Inuit diet in Greenland consists mainly of fish and marine mammals, rich in vitamin D. Vitamin D has anti-inflammatory capacity but markers of inflammation have been found to be high in Inuit living on a marine diet. Yet, the effect of vitamin D on inflammation in Inuit remains unsettled. This led us to investigate the association between vitamin D and markers of inflammation in a population with a high intake of a marine diet. We studied 535 Inuit and non-Inuit living in West and East Greenland. Information concerning dietary habits was obtained by interview-based FFQ. Blood samples were drawn for analysis of 25-hydroxyvitamin D, high-sensitivity C-reactive protein (hsCRP) and chitinase-3-like protein 1(YKL-40). Participants were divided into three groups based on degree of intake of the traditional Inuit diet. The diet groups (Inuit diet/mixed diet/imported foods) were associated with vitamin D levels in serum (74·2, 69·8 and 52·9 nm; P < 0·001), hsCRP (1·6, 1·4 and 1·3 mg/l; P = 0·002) and YKL-40 (130, 95 and 61 ng/ml; P < 0·001), respectively. YKL-40 level decreased with rising vitamin D level in Inuit (Inuit diet P = 0·002; mixed diet P = 0·011). YKL-40 was lower in groups with higher vitamin D levels after adjusting for other factors known to influence inflammation (P < 0·001). This was not seen for hsCRP. In conclusion, vitamin D and markers of inflammation vary in parallel with the intake of the marine Inuit diet. Vitamin D levels were inversely associated with YKL-40 levels, but no association with hsCRP was found. The hypothesised anti-inflammatory effect of vitamin D was not supported. Other factors in the marine diet may be speculated to influence inflammation.

Vitamin D status as measured by plasma 25-hydroxyvitamin D (25(OH)D) is important to human health. Circumpolar people rely on dietary sources and societal changes in the Arctic are having profound dietary effects. The objective of the present study was to determine plasma 25(OH)D status and factors important to plasma 25(OH)D in populations in Greenland. Inuit and non-Inuit aged 50–69 years in the capital in West Greenland (latitude 64°15′N) and in a major town and remote settlements in East Greenland (latitude 65°35′N) were surveyed. Supplement use and lifestyle factors were determined by questionnaires. Inuit food scores were computed from a FFQ of seven traditional Inuit and seven imported food items. 25(OH)D2 and 25(OH)D3 levels were measured in the plasma. We invited 1 % of the population of Greenland, and 95 % participated. 25(OH)D3 contributed 99·7 % of total plasma 25(OH)D. Non-Inuit had the lowest median plasma 25(OH)D of 41 (25th–75th percentile 23–53) nmol/l compared with 64 (25th–75th percentile 51–81) nmol/l in Inuit (P< 0·001). Plasma 25(OH)D was below 20 and 50 nmol/l in 13·8 and 60·1 % of participants, respectively, with Inuit food item scores below 40 % (P< 0·001), and in 0·2 and 25·0 % of participants, respectively, with higher scores (P< 0·001). The Inuit diet was an important determinant of plasma 25(OH)D (P< 0·001) and its effect was modified by ethnicity (P= 0·005). Seal (P= 0·005) and whale (P= 0·015) were major contributors to plasma 25(OH)D. In conclusion, a decrease in the intake of the traditional Inuit diet was associated with a decrease in plasma 25(OH)D levels, which may be influenced by ethnicity. The risk of plasma 25(OH)D deficiency in Arctic populations rises with the dietary transition of societies in Greenland. Vitamin D intake and plasma 25(OH)D status should be monitored.