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

Vitamin D levels in a large Mediterranean cohort: reconsidering normal cut-off values

“…58 The most intriguing finding of our study was the suboptimal 25-(OH)D values observed in both genders (males=19.48±9.51 and females=18.01±9.01, ng/ mL±SD), contrary to what would be expected in an area with abundant sunshine and a population prone to outdoor activities. This is in line with other studies indicating that 25-(OH)D levels in Mediterranean countries, 12,55,[59][60][61][62][63][64] and in Greece specifically, 28,64 are often surprisingly low, with reported levels as low as 9.4 ng/mL in males and 8.5 ng/mL in females in autumn. 65 Our results are also in agreement with published reports suggesting that insolation in a certain region may not be the sole, or even an accurate, predictor of the VitD status.…”

“…2,10,[26][27][28] In our cohort also, a significant seasonal variation of 25-(OH)D was evident (p<0.001) ( Figure 1B, Table 3). Interestingly, there was one major peak throughout the year, with values significantly increasing from April to August and linearly decreasing thereafter, roughly corresponding to maximum insolation and UV index on the island of Crete (source http://www.bing.com/ search?q=weather).…”

“…The globally reported seasonal fluctuation of 25-(OH)D levels, 28,[33][34][35][36][37][38][39][40][41] attributed to cutaneous synthesis of VitD being affected by geographical location and season, 2,26,27,42 was also observed in our cohort. Consequently, given this universally observed seasonal variation of VitD levels, caution should be exercised when single "snapshot" measurements of 25-(OH) D form the basis for recommendations on VitD supplementation and associations with various health outcomes.…”

Parathyroid hormone response to severe vitamin D deficiency is associated with femoral neck bone mineral density: an observational study of 405 women with hip-fracture

“…11 Parathyroid hormone (PTH) excess can contribute to bone loss 12 and possibly to fall risk 13 in patients with vitamin D depletion because the latter is an established cause of secondary hyperparathyroidism. 14,15 However, PTH elevation is not always found in vitamin D depletion: several patients with severe vitamin D deficiency do not have PTH excess, as first shown by Sahota et al 16 and confirmed by several recent reports. [17][18][19][20] At present, the reasons why vitamin D depletion leads to either secondary hyperparathyroidism or normal PTH levels in individual subjects are not clear.…”

“…12,14 The clinical significance of our results rests on the excess of bone loss found in hip-fracture women with vitamin D depletion who developed secondary hyperaparathyroidism versus those who did not. Besides bone loss, other adverse consequences have been associated with PTH excess in hip-fracture patients, who are frail subjects 7,8,22 with a high risk of recurrent falls 23 and fractures, 4,24 several comorbidities, 22 and reduced life expectancy.…”