The inhibitory effect of soy products on nonheme iron absorption in man

Am J Clin Nutr. 1981 Dec;34(12):2622-9. doi: 10.1093/ajcn/34.12.2622.


Radioiron absorption studies were performed in male volunteer subjects to determine the effect on nonheme iron absorption of various semipurified proteins. When egg albumen and casein were substituted in protein-equivalent quantities in a semisynthetic meal, similar mean absorptions of 2.5 and 2.7% were observed. In contrast, isolated soy protein reduced absorption sharply, to an average of 0.5%. When egg albumen in the semisynthetic meal was replaced with full fat soy flour, textured soy flour, and isolated soy protein, absorption fell from 5.5 to 1.0, 1.9, and 0.4%, respectively, indicating an inhibitory effect by a wide range of soy products. The effect of substituting textured soy flour for meat in a meal containing a hamburger, french fries, and a milkshake was also evaluated. With 3:1 and 2.1 ratios of meat to unhydrated textured soy flour, absorption decreased by 61 and 53%, respectively. The soy products tested in this study have a pronounced inhibitory effect on the absorption of nonheme iron.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Absorption
  • Adolescent
  • Adult
  • Caseins / pharmacology
  • Dietary Proteins / pharmacology*
  • Flour
  • Glycine max*
  • Humans
  • Iron / metabolism*
  • Male
  • Middle Aged
  • Ovalbumin / pharmacology


  • Caseins
  • Dietary Proteins
  • Ovalbumin
  • Iron