Vitamin D deficiency in South Europe: effect of smoking and aging

The main source of vitamin D is synthesis in the skin during exposure to ultraviolet radiation. The existence of photoaggravated diseases and the increasing incidence of skin cancer have prompted recommendations to avoid the sun. Here, we study the status of vitamin D in a healthy population and its relation to their habits of sun exposure. To do so, we designed a cross-sectional study that included 177 healthy people. We analyzed parameters about demographic data, sun exposure, and protection habits and estimated vitamin D dietary intake. We performed blood tests to measure serum 25-hydroxyvitamin D [25(OH)D], calcium, phosphorus, and intact parathyroid hormone. Mean levels (± standard deviation) of 25(OH)D were 24.0 (± 8.5) ng/ml. Seventy-six percent of the population did not reach recommended levels of vitamin D (30 ng/ml), including 4.5% who were vitamin D deficient (< 10 ng/ml). Levels were higher in young people (P = 0.04) and those with more sun exposure (P = 0.04). Smoking was associated with an increased risk of hypovitaminosis D (odds ratio, 1.8; 95% confidence interval, 1.00-3.35). On the basis of our findings, we should consider the risk of hypovitaminosis when we recommend sun avoidance, especially in some risk groups, because the sun is the most important source of this vitamin.