Height and height Z-score are related to calcium absorption in five- to fifteen-year-old girls

Context: Understanding the relationship between calcium absorption and growth has been limited. We have developed a database of calcium absorption measurements in 315 girls aged 5.0 - 15.0 yr. Design: We have used this database to assess the relationship between height, its age- and gender-normalized value (height Z-score), and calcium absorptive efficiency. Results: Overall, height was significantly related to calcium absorption ( corrected for calcium intake, age, Tanner, stage, and ethnicity) (P = 0.001). Similarly, height Z-score was significantly related to calcium absorption (P < 0.007). About 3 - 3.5% of the variability (eta(2)) of absorption was associated with height or height Z-score. We found that calcium absorption was significantly lower in girls with height Z-score equal to or less than zero compared with those with a height Z-score more than zero (difference, 3.9 +/- 1.4%, mean +/- SEM; P = 0.007). Limiting the analysis to those girls in which Tanner staging was performed or those age 9 yr or older did not substantively affect these relationships. Conclusion: These results indicate that a small but significant component of the variability in calcium absorption is due to height. Identifying genetic risk factors for lowered calcium absorption during growth could lead to individual approaches for prevention of inadequate bone mass.