Vitamin D deficiency in Spain: a population-based cohort study

Background: Vitamin D deficiency is common worldwide. No homogenous reference values have yet been established and no studies of values have been conducted in Spain involving a large number of participants. Objective: To study the population concentrations of vitamin D in a representative sample of the Spanish population. Subjects/Methods: The study involved two cohorts from Spain, the Asturias study and the Pizarra study, which are two prospective, population-based studies involving 2260 participants. In 1262 subjects (age: 20-83 years) we studied 25-hydroxyvitamin D, intact parathyroid hormone (iPTH), calcium, phosphorus and creatinine. Results: The median population values of 25-hydroxyvitamin D and iPTH were 22.46 ng/ml and 42.29 pg/ml, respectively. The values of 25-hydroxyvitamin D were significantly higher in summer and correlated with age (beta = -0.05 +/- 0.01, P < 0.0001), creatinine (beta = 6.42 +/- 1.17, P < 0.0001) and iPTH (-0.07 +/- 0.01, P < 0.0001), but not with calcium, phosphorus or sex. The increase in iPTH with age was seen whatever the values of 25-hydroxyvitamin D, and was greater in the older persons. The concentration of iPTH rose continuously with effect from 25-hydroxyvitamin D values below approximate to 30 ng/ml. Values above approximate to 35 ng/ml were associated with a significantly lower concentration of iPTH. Conclusions: One-third (33.9%) of the Spanish population may be at risk for Vitamin D deficiency. The 25-hydroxyvitamin D values above 30 ng/ml can safely discard 'hyper PTH'. The increase in iPTH concentration is greater in older persons for similar values of 25-hydroxyvitamin D. European Journal of Clinical Nutrition (2011) 65, 321-328; doi:10.1038/ejcn.2010.265; published online 22 December 2010