Calcium is the key determinant of the quality of the skeleton because it gives it its stiffness properties. Thus, because of the major public health concern represented by impairment of the musculoskeletal system among seniors, optimizing the calcium status must be ensured by covering the needs identified by the recommended dietary intake, but also by potentiation of its bioavailability. Therefore, any strategy that can promote calcium absorption must be considered. This is why food source of calcium and calcitherapy must be associated with vitamin D, which in its di-hydroxylated form is involved in the transport of the mineral through the enterocyte in the digestive tract. This concept is well established. On the other hand, recent studies indicate that 25(OH) D may directly modulate bone cells that possess not only specific receptors (VDR), but also the 1alpha-hydroxylase necessary for the transformation of the molecule into its active metabolite. Regarding the demonstration of the skeletal effects of vitamin D, it is clear that secondary hyperparathyroidism that develops in a situation of vitamin D deficiency is extremely harmful because it causes an acceleration of bone resorption. This is why, in such a situation, supplementation may improve bone mass and remodeling, even though the effect is small. However, scientists agree that supplementation combining calcium and vitamin D may reduce the risk of fracture, depending on the intensity of the initial consumption threshold, the prescribed dose and course of treatment adherence. This apparent disparity between bone mass and fracture risk could be explained by the cumulative effects of the vitamin on the skeleton with the impact on extra -osseous targets, eg, muscle, since the risk of falling decreases when taking in vitamin. In addition, according to recent data, vitamin D may also reduce body fat and insulin resistance, which are also risk factors for bone health. In summary, even if all the cellular and molecular mechanisms are not fully understood, the benefit of vitamin D supplementation is real in case of deficiency (especially in the elderly). It is therefore obvious that we must be vigilant in respect of the recommendations. In addition, acorrection of any deficiencies should precede or accompany any therapy targeting bone disease. (C) 2014 Societe france aise de nutrition. Published by Elsevier Masson SAS. All rights reserved.
