Optimizing Absorption of Oral Iron Supplements

Although iron deficiency is a common hematologic disorder, our understanding of factors affecting absorption of oral iron supplements is incomplete. Researchers studied the fractional absorption of iron from oral iron supplements administered under six different conditions in 34 healthy, nonanemic, iron-deficient females (median age, 28), each of whom served as her own control. The conditions were separated by at least several days, and in each, the oral supplements contained 100 mg of radiolabeled ferrous fumarate.

Compared with the control condition — overnight fasting followed by a morning iron dose taken with water three hours before coffee or breakfast — a morning dose taken with either 80 mg or 500 mg of ascorbic acid significantly improved iron absorption by about 30%. The higher dose did not yield significantly higher absorption. All other strategies reduced iron absorption: afternoon dosing by 37%; coadministration with coffee in the morning by 54%; administration in the morning with coffee, 90 mg of ascorbic acid, and food by 66%.