ИСТИНА

We collected data on vitamin D status (as blood serum 25(OH)D concentration) of various groups of population of the RF on the territories lying above the 60°N. The data collectively represent 3730 individuals of post-traditional rural and urban residence (ethnic Russians, Karelians and Komi), and 1030 persons belonging to 17 ethnic groups of indigenous peoples of North (from Chukotka to Nenets AO). A population of tempered climate (48-59°N) made up a reference group. We examined the correlation of the populational levels of vitamin D with geographic latitude in 29 groups of Russians living in the sub-Arctic areas. There was no association found. The median values of 25(OH)D concentrations are becoming lower from summer to winter and reach the minimum in February. Kruskal–Wallis one-way analysis of variance confirmed that the season is a significant factor (p = 0.0081). A significant correlation was found between the length of daylight and the group-average serum concentration of 25(OH)D (Rsp = 0.64, p = 0.0017, n = 21). The levels of 25(OH)D in the groups of the indigenous people living in towns and large settlements vary within the range of group-average fluctuations seen among urban Russians and Karelians from more southern regions (57-59°N). The average 25(OH)D content in the groups of indigenous northerners, like in the temperate zone population, corresponds with the length of daylight. The vitamin D level was lower during the polar night (0-3 hours of daytime) than when the daytime was 8 hours and more (p < 0.05). Among the indigenous people, decrease in the content of 25(OH)D associated with the abandonment of traditional food. The traditional diet of inland Arctic indigenous population, which based on venison and river fish, effectively prevents hypovitaminosis D.