“…Groen and Taylor (20) have demonstrated, however, that the difference is largely due to iron retained because of adsorption by the mucosa, rather than to actual absorption. While the third method has certain advantages, it not only is time consuming and indirect, but has recently been challenged on the ground that much more iron is actually absorbed and retained by the body following therapeusis than is utilized for immediate hemoglobin synthesis (12,21,22,23).…”