Vitamin D in the Middle East and North Africa

PURPOSE

The Middle East and North Africa (MENA) region registers some of the lowest serum 25‑hydroxyvitamin D [25(OH)D] concentrations, worldwide. We describe the prevalence and the risk factors for hypovitaminosis D, completed and ongoing clinical trials, and available guidelines for vitamin D supplementation in this region.

METHODS

This review is an update of previous reviews published by our group in 2013 for observational studies, and in 2015 for randomized controlled trials (RCTs) from the region. We conducted a comprehensive search in Medline, PubMed, and Embase, and the Cochrane Library, using MeSH terms and keywords relevant to vitamin D, vitamin D deficiency, and the MENA region, for the period 2012-2017 for observational studies, and 2015-2017 for RCTs. We included large cross-sectional studies with at least 100 subjects/study, and RCTs with at least 50 participants per arm.

RESULTS

We identified 41 observational studies. The prevalence of hypovitaminosis D, defined as a 25‑hydroxyvitamin D [25(OH)D] level below the desirable level of 20 ng/ml, ranged between 12-96% in children and adolescents, and 54-90% in pregnant women. In adults, it ranged between 44 and 96%, and the mean 25(OH)D varied between 11 and 20 ng/ml. In general, significant predictors of low 25(OH)D levels were female gender, increasing age and body mass index, veiling, winter season, use of sun screens, lower socioeconomic status, and higher latitude.We retrieved 14 RCTs comparing supplementation to control or placebo, published during the period 2015-2017: 2 in children, 8 in adults, and 4 in pregnant women. In children and adolescents, a vitamin D dose of 1000-2000 IU/d was needed to maintain serum 25(OH)D level at target. In adults and pregnant women, the increment in 25(OH)D level was inversely proportional to the dose, ranging between 0.9 and 3 ng/ml per 100 IU/d for doses ≤2000 IU/d, and between 0.1 and 0.6 ng/ml per 100 IU/d for doses ≥3000 IU/d. While the effect of vitamin D supplementation on glycemic indices is still controversial in adults, vitamin D supplementation may be protective against gestational diabetes mellitus in pregnant women. In the only identified study in the elderly, there was no significant difference between 600 IU/day and 3750 IU/day doses on bone mineral density. We did not identify any fracture studies.The available vitamin D guidelines in the region are based on expert opinion, with recommended doses between 400 and 2000 IU/d, depending on the age category, and country.

CONCLUSION

Hypovitaminosis D is prevalent in the MENA region, and doses of 1000-2000 IU/d may be necessary to reach a desirable 25(OH)D level of 20 ng/ml. Studies assessing the effect of such doses of vitamin D on major outcomes, and confirming their long term safety, are needed.

Clinical practice guidelines for vitamin D in the United Arab Emirates

In the UAE and the Gulf region in general, there are several intricate public health issues in the context of vitamin D deficiency that needs to be addressed. Changes in lifestyle such as diet, lack of exercise, cultural habits, avoiding sun exposure due to excessive heat, and other risk factors predispose those who live in GULF countries, such as Emiratis likely to becoming vitamin D deficient. Consequently, the prevalence of vitamin D deficiency is high, and new guidelines are needed to overcome this major public health issue. Peer-reviewed papers related to guidelines and those vitamin D-related papers relevant to the Middle-Eastern region were extracted from multiple research databases using key words according to the general guidelines from the Preferred Reporting Items for Systematic Analysis. This guideline was prepared focusing on the United Arab Emirate and the Gulf populations, to overcome the high incidence of vitamin D deficiency and to improve overall health. We recommend the following vitamin D supplementations for different groups of people: (A) Breastfed infants supplement with 400 IU/day up to age 6 months, and 400-600 IU/day between 6 and 12 months, depending on daily intake of total vitamin D and sun exposure; (B) for children and adolescents of age 1-18 years supplement with 600-1000 IU/day depending on the body weight; (C) adults greater than 18 years', supplementation with 1000-2000 IU/day is recommended, while, (D) the elderly (over 65 years) should be supplemented with 2000 IU/day, throughout the year; (E) pregnant and breast feed women, 2000 IU/day from the first trimester of pregnancy. (F) Premature infants, supplementation of 400-800 IU/daystart from the first days of life. (G) For obese, individuals and those with metabolic syndrome, supplementation of 2000 IU/day (H) For individuals with dark skin complexions and for night workers, supplementation of 1000-2000 IU/day (25-50μg/day), throughout the year, depending on body weight. The goal of supplementation is to achieve and longer term maintenance of serum 25(OH)D concentration of 30-50ng/mL.