Chapter 28 Chapter 28 Nutrition and Risk for Osteoporosis Copyright © 2013 Elsevier Inc. All rights reserved.

FIGURE 28.1 Schematic representation of the interplay of the principal factors thought to be important in hip fracture. Asterisks denote factors with a recognized nutritional determinant. Source: Copyright Robert P. Heaney, Used with permission. 2

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.2 Diagrammatic depiction of the bowing of vertical trabeculae that occurs in loading. The presence of a resorption bay on the surface of a trabeculae creates local weakness conducive to microfracture. Source: Copyright Robert P. Heaney, Used with permission. 3

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.3 Changes in calcium concentration of the diet associated with the agricultural/pastoral revolution. Source: Copyright Robert P. Heaney, Used with permission. 4

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.4 Threshold behavior of calcium intake. A. Theoretical relationship of bone accumulation to intake. Below a certain value − the threshold − bone accumulation is a linear function of intake (the ascending line); in other words, the amount of bone that can be accumulated is limited by the amount of calcium ingested. Above the threshold (the horizontal line), bone accumulation is limited by other factors, and is no longer related to changes in calcium intake. B. Actual data from two experiments in growing rats, showing how bone accumulation does, in fact, exhibit a threshold pattern. Source: redrawn from data in Forbes RM et al. [65]. Copyright Robert P. Heaney, Used with permission. 5

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.5 A. Schematic calcium intake and retention curves for three life stages. Retention is greater than zero during growth, zero at maturity, and may be negative during involution. Asterisks represent minimum daily requirement. B. The involution curve only. Point B designates an intake below the maximal calcium retention threshold, whereas point A designates an intake above the threshold. Source: Copyright Robert P. Heaney, Used with permission. 6

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.6 Calcium input from intestinal absorption and bone resorption in adolescent girls studied at two calcium intakes. The rise in absorbed calcium at the higher intake produced a nearly identical fall in the amount of calcium released from bone. ECF: extracellular fluid. Source: Drawn from published data of Wastney et al. [81]. Copyright Robert P. Heaney, Used with permission. 7

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.7 The relationship of calcium intake, on the horizontal axis, to calcium retention (balance), on the vertical axis, for a subset of the adolescents described by Matkovic and Heaney [57]. Note that, despite the “noisiness” that is inevitable in measurements of balance in humans, there is clear evidence of an intake plateau, as observed in the animal experiments of Fig, Note also that, for this age, the threshold of the plateau occurs at about 1500 mg Ca/day. Source: Copyright Robert P. Heaney, Used with permission. 8

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.8 Regression lines for the subthreshold regions of the intake–balance relationships in infants, children, adolescents, and young adults, from the data of Matkovic and Heaney [57]. Source: Copyright Robert P. Heaney, Used with permission. 9

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE 28.9 Partition of age-related bone loss in a typical postmenopausal woman with an inadequate calcium intake. Based upon a model described in detail elsewhere [100]. Source: Copyright Robert P. Heaney, Used with permission. 10

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE Partition of variance in calcium balance in normal women among the input–output processes involved in calculation of balance. EFCa: endogenous fecal calcium. Source: Copyright Robert P. Heaney, Used with permission. 11

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE Calcium absorption fraction as a function of serum 25(OH)D from three published studies [185–187]. Source: Copyright Robert P. Heaney, Used with permission. 12

Copyright © 2013 Elsevier Inc. All rights reserved. FIGURE Relationship of calcium intake, net calcium gain across the gut, and vitamin D-mediated, active calcium absorption. Each of the contours represents a different level of active absorption above a baseline passive absorption of 12.5%. (The values along each contour represent the sum total of passive and variable active absorption.) The horizontal, dashed lines indicate zero and 200 mg/day net absorption, respectively. The former is the value at which the gut switches from a net excretory to a net absorptive mode, and the latter is the value needed to offset typical urinary and cutaneous losses in mature adults. Source: Copyright Robert P. Heaney, Used with permission. 13