Long-term calcium supplementation does not affect the iron status of 12-14-y-old girls.
BACKGROUND
Single-meal studies have established that calcium has an acute inhibitory effect on the absorption of iron. However, there is growing evidence that high calcium intakes do not compromise iron status.


OBJECTIVE
We evaluated whether long-term calcium supplementation taken with the main meal affected biomarkers of iron status in adolescent girls with high requirements of both iron and calcium.


METHODS
The study was a randomized, double-blind, placebo-controlled trial of supplementation with 500 mg Ca/d for 1 y among 113 adolescent girls aged 13.2 +/- 0.4 y at enrollment. Participants were advised to take the supplement with their evening meal, which usually contributes the majority of dietary iron. Iron status was assessed at baseline and after 1 y of supplementation by measuring hemoglobin and serum concentrations of ferritin and transferrin receptors (TfRs).


RESULTS
The mean (+/-SD) hemoglobin at enrollment was 134 +/- 9 g/L, geometric mean serum ferritin was 26.3 microg/L (interquartile range: 18.6-39.4 microg/L), and serum TfR was 4.19 mg/L (3.52-5.10 mg/L). Daily calcium supplementation had no effect on the least-squares mean concentrations of iron-status markers adjusted for their baseline values (hemoglobin: 136 and 134 g/L, P = 0.31; ferritin: 25.4 and 26.1 microg/L, P = 0.73; TfR: 4.1 and 4.4 mg/L, P = 0.12; and the ratio of TfR to ferritin: 160 and 161 in the calcium and placebo groups, respectively; P = 0.97).


CONCLUSIONS
Although it remains to be shown in iron-deficient persons, long-term iron status does not seem to be compromised by high calcium intakes.
Mølgaard
Christian
C
Department of Human Nutrition, Centre for Advanced Food Studies, Royal Veterinary and Agricultural University, Frederiksberg, Denmark. cm@kvl.dk
Kaestel
Pernille
P
Michaelsen
Kim F
KF
D000293:Adolescent; D000886:Anthropometry; D001823:Body Composition; D002136:Calcium, Dietary / Q000008:administration & dosage / Q000494:pharmacology*; D002648:Child; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005293:Ferritins / Q000097:blood*; D006801:Humans; D019266:Iron, Dietary / Q000097:blood*; D009752:Nutritional Status; D011627:Puberty
D002136:Calcium, Dietary; D019266:Iron, Dietary; D005293:Ferritins