Calcium intake is weakly but consistently negatively associated with iron status in girls and women in six European countries

Several studies indicate that intake of calcium can inhibit iron absorption especially when taken simultaneously. In the CALEUR study, a cross-section al study among girls (mean 13.5 y) and young women (mean 22.0 y) in six Eur opean countries, the association between calcium intake and iron status was studied. In 1,080 girls and 524 women, detailed information on calcium int ake was collected by means of a 3-d food record, and serum ferritin, serum iron, serum transferrin and transferrin saturation were measured as indicat ors of iron status. The mean levels of serum iron, ferritin and transferrin were 15.8 +/- 6.1 mmol/L, 34.5 +/- 19.1 mu g/L and 3.47 +/- 0.47 g/L, resp ectively, in girls and 16.9 +/- 7.5 mmol/L, 40.2 +/- 30.5 and mu g/L, 3.59 +/- 0.60 g/L, respectively, in women. A consistent inverse association betw een calcium intake and serum ferritin was found, after adjusting the linear regression model for iron intake, age, menarche, protein, tea and vitamin C intake and country, irrespective of whether calcium was ingested simultan eously with iron. The adjusted overall regression coefficients for girls an d women were -0.57 +/- 0.20 and -1.36 +/- 0.46 per 100 mg/d increase in cal cium intake, respectively. Only in girls, transferrin saturation as a measu re for short-term iron status was inversely associated with calcium intake (adjusted overall coefficient -0.18 +/- 0.08). However, analysis per countr y separately showed no consistency. We conclude that dietary calcium intake is weakly inversely associated with blood iron status, irrespective of whe ther calcium was ingested simultaneously with iron.