Vitamin D deficiency in white, apparently healthy, free-living adults in a temperate region.

OBJECTIVE The precise incidence of vitamin D deficiency is not known, primarily because there is no consensus on the optimal levels of serum 25(OH)Vitamin D. The aim of the present study was to determine the incidence of vitamin D deficiency in a large group of normal adult volunteers residing in a typical temperate region. DESIGN-METHODS: In 625 healthy, free living adults (553 women, 72 men, aged 18-85 years), serum 25(OH)Vitamin D and 1-25(OH)2 Vitamin D (RIA), plasma intact PTH (ECLIA) and routine chemistries (multianalyser) were determined at baseline once during a whole year. In a subgroup of 36 subjects, a vitamin D loading (suppression) test was also performed to define the lower normal values for these two Vitamin D metabolites. RESULTS The estimated lower normal values, based on the results of the vitamin D2 loading test, were 22 ng/ml (55 nmol/L) for 25(OH)Vitamin D and 24.6 pg/ml (59 pmol/l) for 1-25(OH)2 Vitamin D. During the whole year, the incidence of low values was 57.7% for 25(OH)Vitamin D and 33.2% for 1-25(OH)2 Vitamin D. A highly significant (p<0.001) positive linear correlation of serum 25(OH)Vitamin D with 1-25(OH)2 Vitamin D values and a negative correlation of 25(OH)Vitamin D with intact PTH was observed in the entire group and separately in women without or with osteoporosis and osteopenia. CONCLUSION Most of the white normal adults living in a temperate region were vitamin D deficient. The observed correlations between serum concentrations of 25(OH)Vitamin D and 1-25(OH)2 Vitamin D as well as of 25(ΟΗ)Vitamin D and intact PTH, suggest that 25(OH)Vitamin D is implicated not only in 1-25(OH)2 Vitamin D production but also in PTH secretion.