Vitamin D deficiency and insufficiency in Africa and the Middle East, despite year-round sunny days.

Exposure to sunlight, specifically ultraviolet B (UVB), is essential for cutaneous vitamin D synthesis. Despite significant daily sunlight availability in Africa and the Middle East, persons living in these regions are frequently vitamin D insufficient or deficient. Vitamin D insufficiency (25-hydroxyvitamin D (25(OH)D) between 15 and 20 ng/mL (37.5-50 nmol/L)) has been described in various population groups, ranging from 5% to 80%. Risk factors include traditional dress and avoidance of sunlight exposure, and multiple dietary factors as a result of specific cultural beliefs. Vitamin D resistance due to calcium deficiency mechanisms has been described in similar population groups, which may lead to hypovitaminosis D. Should the new diseases related to hypovitaminosis D prove to be truly associated, Africa and the Middle East will become an epicentre for many of these conditions. Urgent attention will need to be paid to cultural dress and dietary behaviours if hypovitaminosis D is to be taken seriously. Should such factors not be correctable, new strategies for supplementation or food fortification will have to be devised.