Effects of Long-Term Calcium Supplementation on Iron Status in Adolescent Females

Abstract

LEARNING OUTCOME: The 4-year calcium supplementation did not affect serum ferritin and iron deficiency anemia indices in adolescent females. The recent recommendations of National Institutes of Health for increasing calcium (Ca) intake in adolescent females to 1200-1500 mg/day raised a concern about its effects on other minerals, namely iron. The previous studies examining the effects of Ca supplementation on iron status in humans resulted in mixed conclusions. The objective of our study was to investigate the effects of Ca supplementation on iron status during a 4-year period. A sample of 354 healthy, Caucasian females were enrolled in the study at the average age of 10.8 y; one half was randomly assigned to receive 1000 mg/d Ca as Ca citrate malate and another half placebo. Blood was drawn once a year and serum ferritin was analyzed by the automated procedure (Hitachi Analyzer), while red blood cell indices and hemoglobin were determined at the end of the 4-year follow-up. The subjects completed 3-day dietary records annualy, which were analyzed on Nutritionist III. The average annual compliance with pill intake was 70%. Table presents yearly data (mean±SD): There was no statistical difference between placebo and Ca supplemented group in corresponding hemoglobin (13.4±0.8 vs. 13.2±0.9, p= 0.1), hematocrit (38.5±2.4 vs. 37.9±2.5, p=0.2), red blood cell count (4.4±0.3 vs. 4.4±0.3, p=0.3), mean corpuscular volume (86.6±3.5 vs. 86.5±4.0, p=0.8), and mean corpuscular hemoglobin concentration (34.8±0.6 vs. 34.7±0.7, p=0.1). Our results indicate that long-term (4 years) calcium supplementation in adolescent females has no effect on iron stores, as measured by serum ferritin, or indices of iron deficiency anemia.