Soybeans Today January 1998
Soy Protein Carries Essential Mineral
By Howell Medders
Many Americans, especially children, have too
little iron in their diet, even though they consume a host of
"iron-fortified" products, and iron deficiency is a major health problem in many
less developed countries where red meat is rarely eaten.
"The existence of iron deficiency anemia in the U.S. indicates that the iron in
many fortified foods is not biologically available," says Dr. Navam Hettiarachchy, a
University of Arkansas Division of Agriculture food scientist.
Iron is not biologically available if it is part of a molecule that passes through the
body undigested.
Hettiarachchy is conducting research supported by the Arkansas Soybean Promotion Board
to produce a soy protein-based iron carrier that will increase the bioavailability of iron
in fortified foods.
"An iron-carrying soy protein isolate will further enhance the use of soy proteins
as a meat substitute in infant formula, wheat flour and in many other products," she
said.
The market for an economical iron carrier that is proven to be highly digestible could
include iron fortification of staple foods for much of the worlds population, she
added.
The presence of phytic acid in soy protein inhibits the bioavailability of iron by
forming a stable iron-phytate complex that does not release iron for absorption by the
body, Hettiarachchy says. The U of A research team she leads has developed an iron-bound
soy protein isolate with very low phytic acid, and laboratory tests indicate it is highly
digestible.
The bioavailability of the iron delivered to the body by the soy protein isolate will
require confirmation in animal studies, Hettiarachchy said.
Rats with low known levels of iron in their blood will be given either a soy-based
iron-fortified diet or a control diet containing a known amount of bioavailable iron. The
amount of iron in the rats blood at the end of the study will tell how much they
absorbed from each diet.
Other studies will measure the iron-carrying protein isolates shelf life and how
it responds to changes in temperature and pH.
Hettiarachchy said she is confident that the test results will enable the researchers
to fine tune procedures for producing a soy protein isolate that will become a widely used
carrier for iron in fortified foods including wheat flour, infant formula, breakfast
cereals and staple products in less-developed countries.
For more information on iron or other essential nutrients, contact your county
Extension office.
Soybeans Today January 1998
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