Long-term Calcium Supplementation Does not Affect the Iron Status of 12-14 year-old Girls

Nutrient requirements for iron and calcium are higher in adolescent girls around the time of menarche. Calcium supplementation can compromise long-term iron status, but few data are available for adolescent girls. The aim of this randomized, double- blind, placebo controlled study was to evaluate whether calcium supplementation affected iron status in 113 Dutch girls aged 12-14 years. Subjects took 500 mg calcium (as calcium carbonate) a day or a placebo with the main daily meal for 1 year. Measures of iron status (concentrations of hemoglobin, serum ferritin, and serum transferrin receptors) were collected at baseline and one year along with dietary calcium intake through a food frequency questionnaire.

The mean hemoglobin level at baseline was 134 grams/liter. Two groups were selected according to their dietary calcium intake: a medium intake group (1,000-1,304 mg/day; n=60) and a low intake group (<713 mg/day; n=53). Calcium supplementation had no effect on iron status in either group. This study shows that calcium supplementation does not alter iron status in iron-sufficient adolescent girls. Additional research is necessary to understand the effect of long-term calcium supplementation on iron status in iron- deficient adolescents.

Funding: Danish government Food and Technology Research Program and Danish Dairy Research Foundation.