ویتامین D در خاور میانه و آفریقای شمالی Vitamin D in the Middle East and North Africa

1. Introduction One of the earliest reports on low 25-hydroxyvitamin D [25(OH)D] concentrations in the Middle East was in a group of apparently healthy young university students from Saudi Arabia, in the early eighties (Sedrani et al., 1983). The vitamin D field has since witnessed an explosion in publications, with a larger number of systematic reviews and meta-analyses than original publications, in the last decade (Holick, 2007; El-Hajj Fuleihan et al., 2015; Ross et al., 2011; Holick et al., 2011; Van Schoor and Lips, 2017; Sperati et al., 2013; Keum and Giovannucci, 2014; Bolland et al., 2014; Mao et al., 2013; Ford et al., 2014; Stubbs et al., 2015; Avenell et al., 2014; Weaver et al., 2016; Zheng et al., 2013; Bjelakovic et al., 2014; Chowdhury et al., 2014; Lips, 2010). The Middle East North Africa (MENA) region spans latitudes from 15 to 39° N. At such latitudes, it would be anticipated that vitamin D synthesis from the skin should be possible over 300/364 days of the year (Tavera-Mendoza and White, 2007). However, some of the lowest reported serum 25(OH)D levels, the metabolite that reflects vitamin D nutritional status, are from this region (Arabi et al., 2010; Bassil et al., 2013; Hoteit et al., 2014; El-Rassi et al., 2012). A recent systematic review of 195 studies, involving over 168,000 participants from 44 countries, revealed mean values < 50 nmol/l (20 ng/ml) in 37% of studies, with higher proportions in the Middle East and Asia (Hilger et al., 2014). Environmental and lifestyle factors account for substantial variations in serum 25(OH)D levels, amounting to 7.5–37.5 nmol/l (3 to 15 ng/ml). In this paper we describe 3 case presentations illustrating presentations for low vitamin D in the region. We then synthesize information based on a comprehensive literature search obtained from: reviews and studies on the prevalence of hypovitaminosis D, vitamin D randomized trials (completed and ongoing), vitamin D and overview guidelines, in the MENA region. The MENA countries, as defined by the World Bank, include: Algeria, Bahrain, Djibouti, Egypt, Jordan, Iran, Iraq, Kuwait, Lebanon, Libya, Malta, Morocco, Oman, Palestine/Israel, Qatar, Kingdom of Saudi Arabia (KSA), Syria, Tunisia, United Arab Emirates (UAE), and Yemen (MENA Countries Definition World Bank, n.d.). Details on literature search, abstract and title screen, eligibility criteria, calculation of weighted mean (WM) and pooled standard deviation (SDp), are presented in Appendix I (Arabi et al., 2010; Bassil et al., 2013; MENA Countries Definition World Bank, n.d.; Chakhtoura et al., 2017a, 2017b; Green, 2011; Weighted Mean Calculation, n.d.; Pooled Standard Deviation Calculation, n.d.).