This chapter discusses ethnic issues and nutrition regarding the have consequences for vitamin D status in different countries and continents. In addition, it addresses the risk groups. Vitamin D status has been determined in numerous studies covering all continents and many countries. When comparing vitamin D status between countries, results from assay differences vary between various studies. The vitamin D status depends on the available amount of ultraviolet light in the sunlight which varies with latitude and season, on actual sunlight exposure and on skin pigmentation, and the use of sunscreen and clothing. This also varies depending on cultural and religious background. The lower the amount of sunlight available, the more nutrition becomes important, especially the consumption of fatty fish, vitamin D-fortified foods, and vitamin D supplements. In the following paragraphs, vitamin D status and the occurrence of vitamin D deficiency will be discussed in different continents, North America, South America, Europe, the Middle East, Asia, Africa, and Oceania. Subsequently studies on vitamin D status in one or more continents performed in a central laboratory will be discussed. In these studies interlaboratory variation in serum 25 (OH)D assays does not play a role. Finally, the chapter sheds light on the consequences, i.e. the part of the population being vitamin-D deficient or vitamin-D-insufficient.
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