Vitamin D in health and disease: the global threat of vitamin D deficient rickets.

Nowadays, infectious diseases are less prevalent in many countries around the world and chronic diseases including obesity, diabetes, behavioral problems and nutritional deficiencies are thought to have become the major and eminent health burdens in both the adult and the young population. Among these, vitamin D deficiency poses a major health problem in children and adolescents globally. In fact, even in countries with high sun and specifically high ultraviolet B (UVB) exposure such as Brasil and Australia vitamin D deficiency rickets has become very prevalent. In Australia this has been attributed to the use of sun protecting ointments and changes in life styles that lead to lesser sun exposure especially in children and young people [1]. In populations with dark skin living, for example, in Africa or the Middle East, the prevalence of vitamin D insufficiency with 25-hydroxyvitamin D (25(OH)D) levels ranging between 15 and 20 ng/ mL (37.5–50 nmol/L) ranges from 5% to 80%. Risk factors to develop nutritional rickets include traditional dress and avoidance of sunlight exposure, and also multiple dietary factors as a result of specific cultural beliefs in many of the affected countries as nutritional rickets may also be caused by inadequate dietary intake of calcium when, for example, milk and milk products are consumed less or are not available [2]. As a result of vitamin D and/or calcium deficiency severe bone disease, stunted growth and even the emergence of autoimmune disease and alterations of the immune system are being observed in many populations.