Calcium absorptive efficiency is positively related to body size.

Abstract

Calcium absorption efficiency is a more important determinant of calcium balance than calcium intake itself. The sources of variability in absorptive performance are only partly elucidated. The aim of the study was to explore the relationship between body size and calcium absorption efficiency. Metabolic studies were performed on an inpatient metabolic unit in an academic health sciences center. One hundred seventy-eight women, with an average age of 50.2 yr, were studied from one to five times and yielded an aggregate data set containing 633 individual studies. Calcium absorption fraction was measured by the dual-tracer method. Observed values were expressed as residuals from predicted values for each woman's actual calcium intake, using the previously published relationship between intake and absorption. Absorption residuals were significantly positively correlated with height, weight, and surface area, and after adjusting for estrogen status, these body size variables accounted for approximately 4% of the total variability. The magnitude of the effect is such that a woman 1.8 m in height would absorb 30+% more calcium from a given intake than a woman 1.4 m tall.