Iron status, menarche, and calcium supplementation in adolescent girls

The effects of growth, menstrual status, and calcium supplementation on iron status were studied over 4 y in 354 girls in pubertal stage 2 who were premenarcheal at baseline (x+/-SD age: 10.8+/-0.8 y). Girls were randomly assigned to placebo or treatment with 1000 mg Ca/d as calcium citrate malate. Anthropometric characteristics, bone mass, and nutritional status were measured biannually; ferritin was measured annually; and red blood cell indexes were determined at 4 y. The simultaneous effects of iron intake and menstrual status on serum ferritin, after change in lean body mass (LBM) was controlled for, were evaluated in subjects in the upper and lower quartiles of cumulative iron intake. The average maximal accumulation of LBM (386 g/mo; 95% CI: 372, 399) occurred 0.5 y before the onset of menarche. Change in LBM was a significant predictor of serum ferritin (P < 0.0001), with a negative influence on iron status (t ratio=-4.12). The 2 fitted mathematical models representing ferritin concentrations of subjects in the upper and lower quartiles of cumulative iron intake were significantly different (P < 0.018). The regression line of the ferritin concentration in menstruating girls with high iron intakes had a less negative slope than the line fit to serum ferritin concentrations in girls with low iron intakes (NS). Serum ferritin concentrations at 0, 1, 2, 3, and 4 y were not significantly different between groups. In addition, there was no significant difference between groups in any of the red blood cell indexes. In summary, growth spurt and menstrual status had adverse effects on iron stores in adolescent girls with low iron intakes (<9 mg/d), whereas long-term supplementation with calcium (total intake: approximately 1500 mg/d) did not affect iron status.