Effect of dietary factors and time of day on iron absorption from oral iron supplements in iron deficient women

Abstract

Guidelines generally recommend taking iron supplements in the morning away from meals and with ascorbic acid (AA) to increase iron absorption. However, there is little direct evidence on the effects of dietary factors and time of day on absorption from iron supplements. In iron-depleted women (n = 34; median serum ferritin 19.4 μg/L), we administered 100 mg iron doses labeled with 54Fe, 57Fe, or 58Fe in each of six different conditions with: (1) water (reference) in the morning; (2) 80 mg AA; (3) 500 mg AA; (4) coffee; (5) breakfast including coffee and orange juice (containing ~90 mg AA); and (6) water in the afternoon. Fractional iron absorption (FIA) from these n = 204 doses was calculated based on erythrocyte incorporation of multiple isotopic labels. Compared to the reference: 80 mg AA increased FIA by 30% (p