Soy protein, phytate, and iron absorption in humans.
The effect of reducing the phytate in soy-protein isolates on nonheme-iron absorption was examined in 32 human subjects. Iron absorption was measured by using an extrinsic radioiron label in liquid-formula meals containing hydrolyzed corn starch, corn oil, and either egg white or one of a series of soy-protein isolates with different phytate contents. Iron absorption increased four- to fivefold when phytic acid was reduced from its native amount of 4.9-8.4 to less than 0.01 mg/g of isolate. Even relatively small quantities of residual phytate were strongly inhibitory and phytic acid had to be reduced to less than 0.3 mg/g of isolate (corresponding to less than 10 mg phytic acid/meal) before a meaningful increase in iron absorption was observed. However, even after removal of virtually all the phytic acid, iron absorption from the soy-protein meal was still only half that of the egg white control. It is concluded that phytic acid is a major inhibitory factor of iron absorption in soy-protein isolates but that other factors contribute to the poor bioavailability of iron from these products.
Hurrell
R F
RF
Nestec Ltd., Nestlé Research Centre, Lausanne, Switzerland.
Juillerat
M A
MA
Reddy
M B
MB
Lynch
S R
SR
Dassenko
S A
SA
Cook
J D
JD
D000042:Absorption / Q000187:drug effects; D000328:Adult; D004044:Dietary Proteins / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007501:Iron / Q000493:pharmacokinetics*; D008297:Male; D010833:Phytic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D010940:Plant Proteins / Q000008:administration & dosage* / Q000737:chemistry; D013025:Glycine max
D004044:Dietary Proteins; D010940:Plant Proteins; D010833:Phytic Acid; D007501:Iron