Vitamin D deficiency among northern Native Peoples: a real or apparent problem?

Abstract

Vitamin D deficiency seems to be common among northern Native peoples, notably Inuit and Amerindians. It has usually been attributed to: (1) higher latitudes that prevent vitamin D synthesis most of the year; (2) darker skin that blocks solar UVB; and (3) fewer dietary sources of vitamin D. Although vitamin D levels are clearly lower among northern Natives, it is less clear that these lower levels indicate a deficiency. The above factors predate European contact, yet pre-Columbian skeletons show few signs of rickets—the most visible sign of vitamin D deficiency. Furthermore, because northern Natives have long inhabited high latitudes, natural selection should have progressively reduced their vitamin D requirements. There is in fact evidence that the Inuit have compensated for decreased production of vitamin D through increased conversion to its most active form and through receptors that bind more effectively. Thus, when diagnosing vitamin D deficiency in these populations, we should not use norms that were originally developed for European-descended populations who produce this vitamin more easily and have adapted accordingly.1

Low vitamin D concentrations among indigenous Argentinean children living at high altitudes

“…Numerous studies have been performed to determine the prevalence of abnormal vitamin D status in children, but only a limited number of studies have been performed in non-Caucasian groups such as Argentinean Indians. Although vitamin D levels are clearly lower among Koya children, similar results were found in Natives from Canada (23). A recent study in Native North American children who lived in a reservation located at 43 • latitude, reported that 97% of them had a vitamin D concentration <30 ng/mL (10) Similarly, a vitamin D concentration <30 ng/mL was found in more than 95% of French Canadian children (11).…”

“…Furthermore, Canadian Cree living in Manitoba have a significantly higher frequency of single nucleotide polymorphisms associated with a low expression of vitamin D receptors than a comparative Caucasian cohort (31). Thus, norms that were originally developed for European descendents may not be accurate models for vitamin D deficiency in American Indian populations (21,23).Our finding that all of the children in SAC had insufficient or deficient vitamin D levels implicates dark skin, high altitudes, or genetic backgrounds; it is unlikely that these findings reflect the catch-up growth of malnourished children because the exclusion of children who were underweight did not alter results.…”

Vitamin D status in Greenland – dermal and dietary donations

“…It has been speculated that the frigid Arctic environment caused a selection of Inuit to adapt to a low calcium diet and low vitamin D (17,34). Most of the changes mentioned above are more recent and are thus not likely to counteract this hypothesized selection.…”

Association of vitamin D receptor gene with anthropometric measures in Komi ethnic group

“…The mean values of the 25 OHD3 content in adolescents (M = 37.9, SD = 12.2 nmol/L, n = 44) were significantly lower than in adults (M = 47.7, SD = 12.0 nmol/L, n = 52; p < 0.001). The mean value of 25 OHD3 in serum remains below 50 nmol/l in both age groups, usually depicted as the lower border of the recom mended level of the vitamin D content (Frost, 2012;Holick, 2007;Roth et al, 2005). The frequencies of FokI, BsmI, and ApaI alleles, as well as TaqαI and VDR genotypes, in the studied sam ple are shown in Table 2.…”

“…Undoubtedly, a significant role in this case is played by the traditional food content with its high vitamin D content in meat, fish, sea mammals, and reindeer fat (Kozlov, Ateeva, 2011;Björn, Wang, 2000). However, the possible role of anthropological (including that determined ethnically and ecologically) characteristics, possibly including the different tissue sensitivity to calciferol (Frost, 2012) and the population specifics of genetic determinants of the D vitamin exchange should be taken into consideration.…”