Introduction
The standard method used to assess vitamin D status is the measurement of 25-hydroxyvitamin D (25OHD) serum concentration, the major circulating metabolite of vitamin D. Opinions regarding the optimal concentration of serum 25OHD vary widely. Generally in Italian studies a cut-off of 30 nmol/L has been used because concentrations of 25OHD below 30 nmol/L were associated with secondary hyperparathyroidism, increased bone turnover, and decreased bone mineral density at the hip, even if many recent studies have shown that serum concentrations of at least 50-75 nmol/L are necessary to maximize intestinal calcium absorption and minimize perturbations in parathyroid hormone (PTH), calcium, and phosphorus homeostasis.
Numerous epidemiological studies have assessed the prevalence of low serum 25OHD concentrations and have indicated that vitamin D inadequacy is a common problem worldwide. Differences in the prevalence of vitamin D inadequacy have been related to a variety of factors, including physiological changes with age, race, body mass index, sun exposure, latitude, and dietary vitamin D intake.
Several studies have compared vitamin D status in different populations and geographical regions, but these comparisons are frequently complicated by differences in assays. Here we review the available data on the prevalence and consequences of hypovitaminosis D (defined as serum 25OHD level below 30 nmol/L) in Italy and some of the strategies for its prevention. When you need your medication buy cialis professional