Title:
Effect of calcium carbonate particle size on calcium absorption and retention in adolescent girls.

Abstract:
Increasing calcium bioavailability by decreasing calcium salt particle size in the supplement may be one way to increase calcium absorption. The aim of the study was to compare (1) large versus small particle size CaCO(3) supplements and (2) small particle size CaCO(3) supplement versus placebo on calcium absorption and retention in adolescent girls.
Thirty-one adolescent girls, aged 11 to 14 years, participated in two 3-week calcium balance periods separated by a 1-week washout period. During both balance periods, the subjects consumed a controlled diet containing 804 mg/d calcium. Using a crossover design, one group (n = 19) received an additional ∼600 mg/d calcium of two ∼300-mg calcium doses as either large particle (18 μm; i.e., standard commercial form) or small particle (13.5 μm) CaCO(3). A second group (n = 12) received ∼600 mg/d calcium from small-particle CaCO(3) or placebo.
The parathyroid hormone suppression curve, following a challenge, from the first arm of the study indicated that calcium absorption from the small particle size CaCO(3) was less than that from the large particle size CaCO(3). The parathyroid hormone suppression curve from the small particle versus placebo arm indicated that calcium absorption from small particle size CaCO(3) was greater than placebo. Calcium balance (Ca intake - [urine Ca + fecal Ca]) demonstrated that the small particle size CaCO(3) supplement increased Ca retention nearly 2-fold compared with placebo (p < 0.05; 496 ± 213 and 256 ± 94 mg/d, respectively). However, there was no significant difference in Ca retention due to small versus large particle size of CaCO(3) (p > 0.05; 349.1 ± 131.6 and 322.0 ± 194.2 mg/d, respectively).
Dietary supplementation with CaCO(3) is effective in increasing calcium absorption and retention compared with placebo. But there is no advantage of small compared with large particle size CaCO(3) on calcium absorption and retention.