Ethnic aspects of vitamin D deficiency.

Vitamin D deficiency has been linked to bone fragility in children and adults, and to an increased risk of chronic diseases. The main sources of vitamin D are the diet and cutaneous synthesis, the latter being the most important one, since foods are relatively poor in vitamin D. The main factors influencing this endogenous production are the seasons, the time of day, latitude and skin phototype. Due to the contribution of sun exposure in maintaining vitamin D levels, it would be expected that this deficiency would be more prevalent in countries at a high latitude; it has been shown, however, that hypovitaminosis D is commonly found in tropical regions such as Brazil. In high latitude regions in which extreme skin phototypes have been compared, the prevalence of vitamin D deficiency is more common in people with originally darker skin who have a natural barrier to the already lower UV irradiation penetrating the skin. In Brazil, particularly in the areas where sun rays are more abundant, the difference in sunlight exposure between subjects showed no significant variation in serum 25-hydroxyvitamin D (25OHD).