Background: Dietary ferritin, a protein cage around an iron mineral, is an underestimated source of bioavailable iron. Plant ferritin, the most common dietary ferritin, has not been studied. Iron from animal ferritin is absorbed as well as is iron from FeSO 4 in women. Objective: The objective was to examine iron absorption from purified soybean ferritin. Design: Healthy, nonanemic women (n ҃ 16) were fed a standardized meal (bagel, cream cheese, and apple juice) containing 1 Ci 59 Fe/meal as FeSO 4 or (extrinsically labeled) as iron-free soybean ferritin reconstituted with the high phosphate characteristic of plant ferritin (iron:phosphorus ҃ 4:1). Iron-free, apo-soybean ferritin was prepared (with the use of thioglycolic acid and extensive dialysis) from purified ferritin. In a randomized crossover design, the other labeled meal, which contained FeSO 4 or ferritin, was given after 4 wk. The subjects received 140 g Fe as ferritin (2.5 mg) or as FeSO 4 . After 28 d, whole-body 59 Fe and 59 Fe in red blood cells were measured before and after dosing. Results: There was no significant difference in whole-body iron absorption from soybean ferritin (29.9 Ȁ 19.8%) and that from FeSO 4 (34.3 Ȁ 23.6%) or in iron absorption calculated from red blood cell incorporation (33.0 Ȁ 20.1% for soybean ferritin and 35.3 Ȁ 23.4% for FeSO 4 ), which confirmed previous results with animal ferritin that was mineralized and labeled similarly. An inverse relation was observed between serum ferritin and iron absorption from both ferritin and FeSO 4 , which suggested that sensors regulating iron absorption respond similarly to iron provided as ferrous salts or as ferritin mineral. Conclusion: Iron from soybean ferritin is well absorbed and may provide a model for novel, utilizable, plant-based forms of iron for populations with a low iron status.Am J Clin Nutr 2006;83: 103-7.

Iron is equally well absorbed from lactoferrin (whether heat-treated or untreated) and ferrous sulfate. Thus, iron provided by dietary lactoferrin is likely to be well utilized in human adults.