Serum ferritin and serum transferrin receptor concentrations, growth and food habits were studied in healthy Swedish boys (n = 103) and girls (n = 124) at the age of 17 y and compared with those in the same adolescents at age 15. Between these ages, serum transferrin receptor increased significantly in both boys and girls. Serum ferritin increased significantly in boys but not in girls. The transferrin receptor/ferritin ratio increased significantly in girls but not in boys, indicating insufficient iron stores in the 17-y-old girls in relation to erythropoiesis and iron needs. Between 15 and 17 y the boys' frequency of consumption of milk and bread decreased, while they more often consumed pasta, cheese and coffee. The girls decreased their frequency intake of fat products, milk and meat. The frequency of meat consumption emerged as the single significant predictor for serum ferritin <12 microg/L in girls, but not in boys. The median daily iron intake, determined in a subsample, decreased in boys from 18.7 to 13.6 mg and in girls from 14.1 to 8.8 mg, and the decrease was to a large extent due to cessation of iron fortification of flour.
Conclusions: The results indicate insufficient iron stores in the 17-y-old girls in relation to erythropoiesis and iron needs, but more favourable iron stores in the boys. The absence of a significant decrease in mean serum ferritin despite rapid growth suggests that the earlier iron fortification of flour only marginally contributed to the iron status of Swedish adolescents of this age group.