S. A. Abrams, I. J. Griffin*, P. M. Davila*, K. M. Hawthorne*. Pediatrics, Baylor College of Medicine, Houston, TX, USA.
We measured calcium absorption in groups of 9 to 12 year-old children who were given diets including at least 240 ml/day of milk or one of two types of calcium-fortified orange juice. One orange juice (OJ-1) contained calcium citrate malate as the calcium source and the other contained a mixture of calcium phosphate and calcium lactate as the calcium source (OJ-2). Drinks were extrinsically tagged with a calcium stable isotope (46Ca). Beverages were given with a breakfast meal including a total of 350-550 mg of calcium. Complete 24-hour dietary calcium intake was determined using weighed dietary records. Fractional absorption was very similar between groups and total absorption was not significantly different (p=0.31 by ANOVA) despite differences in intake (see Table below). Calcium intake was linearly correlated with total daily absorption (r = 0.63) suggesting a benefit to increased calcium intake on total absorption up to as much as 2.2 g/day (see figure below). These findings suggest that these three sources of calcium provide similar bioavailability and lead to comparable levels of daily calcium absorption when included as part of a mixed diet containing calcium intakes comparable to recent dietary recommendations. Calcium intake up to a gram over current recommendations may lead to increased calcium absorption using bioavailable calcium sources. Funded in part by NIAMS (AR43740). Also funded in part by The Minute Maid Company (Houston, TX).
Group Number of Calcium Percent Absorption Total
subjects intake (mg/d) absorption
Milk 40 1268±172 33.7±7.8 429±124
OJ-1 30 1510±255 32.5±10.0 492±157
OJ-2 39 1413±503 33.1±10.3 455±198