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-sectional study among girls (mean 13.5 y) and young women (mean 22.0 y) in six European countries, the association between calcium intake and iron status was studied. In 1,080 girls and 524 women, detailed information on calcium intake was collected by means of a 3-d food record, and serum ferritin, serum iron, serum transferrin and transferrin saturation were measured as indicators 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, respectively, 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 between 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 simultaneously with iron. The adjusted overall regression coefficients for girls and women were -0.57 +/- 0.20 and -1.36 +/- 0.46 per 100 mg/d increase in calcium intake, respectively. Only in girls, transferrin saturation as a measure for short-term iron status was inversely associated with calcium intake (adjusted overall coefficient -0.18 +/- 0.08). However, analysis per country separately showed no consistency. We conclude that dietary calcium intake is weakly inversely associated with blood iron status, irrespective of whether calcium was ingested simultaneously with iron.