Vitamin D-rich marine Inuit diet and markers of inflammation – a population-based survey in Greenland

Abstract

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.

The influence of persistent organic pollutants in the traditional Inuit diet on markers of inflammation

“…Thus, the composition differs markedly from that of the imported diet [ 6 ]. The Inuit diet contains high levels of vitamin D [ 17 , 31 ] and other nutrients such as iodine, selenium and vitamin E [ 16 , 34 ]. However, it has become evident that also the levels of contaminants are high [ 7 ].…”

“…A detailed description of the area of investigation and the subjects in the study has been presented previously [ 13 , 16 , 17 ]. In short, 535 Inuit and non-Inuit, men and women, 50–69 years old participated.…”

Living inside the box: environmental effects on mouse models of human disease

“…An exception to this seems to be the Inuit in the American Subarctic and far Northeast Asia, who have darker skin pigmentation than others living at the same latitude, such as Swedish populations. One hypothesis is that retention of darker pigmentation is a response to the requirement to protect from high UV exposure during the long and intense daylight periods of the arctic summer, but this is compensated for by a diet that is very rich in vitamin D ( Schaebel et al, 2015 ). Concomitant selection for genetic variants associated with this diet and environment ( Fumagalli et al, 2015 ) shows that this population has become extremely adapted both behaviorally and genetically.…”

Adaptation of human skin color in various populations

“…One possible reason is that the dark skin could protect the Inuits from the severe UV exposure because of the long daylight hours in winter and high levels of UV reflection from the snow. While the dark skin is a disadvantage for vitamin D production, plenty of vitamins including vitamin D could be compensated from their diets [ 91 , 92 ]. Another cause could be the founder effect of the ancient East Asian ancestry of the Inuits, who have inhabited the arctic region since nearly 5000 years ago, and had higher melanin production than the European ancestry.…”