Ferritin-iron is released during boiling and in vitro gastric digestion.
Biofortification of staple foods with iron in the form of ferritin-iron is a promising approach to fighting iron-deficiency anemia in developing countries. However, contradictory results regarding iron bioavailability to humans from ferritin are not yet fully clarified. Furthermore, the question has been raised whether ferritin can potentially survive gastric passage intact and be absorbed via a ferritin-specific uptake mechanism. We studied changes of ferritin-iron and protein during cooking and in vitro gastric digestion. Water soluble, native ferritin-iron, measured in different legumes, represented 18% (soybeans) up to maximally 42% (peas) of total seed iron. Ferritin-iron was no longer detectable after boiling the legumes for 50 min in excess water. When the same cooking treatment was applied to recombinant bean ferritin propagated in Escherichia coli, some ferritin-iron remained measurable. During in vitro gastric digestion of recombinant bean ferritin and red kidney bean extract, ferritin-iron was fully released from the protein and dissolved at pH 2. Stability tests at varying pH at 37 degrees C showed that the release of ferritin-iron starts at pH 5 and is complete at pH 2. We concluded that ferritin-iron is efficiently released from the ferritin molecule during cooking and at gastric pH and that it should be absorbed as efficiently as all other nonheme iron in food.
Hoppler
Matthias
M
Laboratory of Human Nutrition, ETH Zurich, Zurich 8092, Switzerland. mhoppler@ethz.ch
Schönbächler
Andrea
A
Meile
Leo
L
Hurrell
Richard F
RF
Walczyk
Thomas
T
D000818:Animals; D001682:Biological Availability; D004063:Digestion; D004355:Drug Stability; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics; D007887:Fabaceae / Q000737:chemistry; D005293:Ferritins / Q000235:genetics / Q000378:metabolism*; D005527:Food, Fortified; D005744:Gastric Acid / Q000378:metabolism; D005753:Gastric Mucosa / Q000201:enzymology; D015870:Gene Expression; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007501:Iron / Q000032:analysis / Q000378:metabolism*; D007700:Kinetics; D010434:Pepsin A / Q000378:metabolism; D027805:Phaseolus / Q000737:chemistry; D011994:Recombinant Proteins / Q000378:metabolism; D013552:Swine
D011994:Recombinant Proteins; D005293:Ferritins; D004492:Edetic Acid; D007501:Iron; D010434:Pepsin A