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Newer Perspectives on Calcium Nutrition and Bone Quality

Creighton University, Omaha, Nebraska
Purdue University, West Lafayette, Indiana

View larger version (25K): [in a new window]   Fig. 1. Plots of incidence of distal forearm fractures in males (A) and females (B) from the data of Khosla et al. [14] among residents of Rochester, Minnesota. The lower line for both panels represents fractures reported in 1969–1971 and the upper line represents fractures reported in 1999–2001. The shaded zones represent the increases in childhood fracture in 3 decades.

View larger version (28K): [in a new window]   Fig. 2. Twelve month changes in 20% tibia cross-section by pQCT and leg BMC by DXA in 3–5 y olds randomized to calcium supplementation or placebo and fine motor vs. gross motor exercise in a 2 x 2 factorial design. There was a significant interaction between activity and Ca supplementation in BMC (P = 0.05). There were significant (P 0.05) activity effects in perisoteal and endosteal circumferences by pQCT and significant Ca x activity interactions for cortical area (P = 0.01) and cortical thickness (P = 0.02). Reproduced with permission from reference 22.

View larger version (14K): [in a new window]   Fig. 3. Diagrammatic illustration of the fact that vertical trabeculae bow slightly when loaded. Resorption pits in the side of such trabeculae serve as stress concentrators, since the prior load must now be borne by a smaller cross-section. The result is a tendency to snap with usual load-bearing activities. Hundreds of such healed or healing trabecular fractures can be found in osteoporotic bone by micro-dissection. (Copyright Robert P. Heaney, 2005. Used with permission.)

View larger version (18K): [in a new window]   Fig. 4. Plots of the cumulative incidence of fractures, redrawn from the studies of Chapuy et al. [37] (bottom) and Dawson-Hughes et al. [38] (top). In both cases, the upper line represents the placebo control subjects, and the lower line represents the calcium and vitamin D-treated subjects. The shaded zones represent the reduction of fracture risk, which, as can be readily seen, starts with the very beginning of treatment. (Copyright Robert P. Heaney, 2004. Used with permission.)

View larger version (15K): [in a new window]   Fig. 5. Schematic redrawing of the change in BMC in the compliant subjects in the study of Johnston et al. [39], with the post-treatment follow-up data from the report of Slemenda et al. [40]. (Data supplied by Dr. C.C.Johnston.) A represents the positive remodeling transient at the beginning of supplementation, and B, the negative transient at its withdrawal. (Copyright Robert P. Heaney, 2005. Used with permission.)