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Iron deficiency is the most common nutrient deficiency
in the world. Yet as a dietary mineral, iron is essential for growth,
development, and performance of daily tasks. Data from the National
Health and Nutrition Examination Surveys, 1988-1994 and 1999-2000, shows
that in the United States 11 to 12 percent of women aged 20 to 49 years
were deficient in iron, and 4 to 5 percent had anemia, which can impair
cognitive and immune functions.
To address the deficiency problem, food manufacturers
enrich flour, maize, and rice and fortify breakfast cereals with iron.
Yet there is little research on the nutritional bioavailability of the
various iron sources used to fortify foods today.
Researchers at the ARS
Grand Forks Human Nutrition Research Center, in Grand Forks, North Dakota,
are seeking new information on the bioavailability of commonly used
iron powders. They are collaborating with SUSTAIN (Sharing U.S. Technology
to Aid in the Improvement of Nutrition) and its partners as part of
an overall review of the bioavailability of elemental iron powders.
For several decades, elemental iron powders have been
the resource of choice for boosting iron content in breakfast cereals.
These powders are produced through several different methods—each
yielding a product with distinct physical properties, which in turn
may affect bioavailability.
Derived from iron ore, elemental iron powders are economical
for producers, and they generally do not disturb the flavor or storage
properties of the products to which they're added. But the traits that
make them less reactive with foods may also decrease their nutritional
bioavailability.
A soluble form of iron known to be highly bioavailable,
yet not itself an elemental iron powder, is ferrous sulfate. Although
relatively inexpensive, it is not commonly used in staple foods because
of its tendency to oxidize, which in turn discolors and degrades foods.
Still, ferrous sulfate's high level of bioavailability serves as a gauge
with which to compare the relative level of absorption of various iron
powders.
"The nutritional bioavailability of these powders
is probably influenced by particle size, density, surface area, chemistry,
and shape," says Janet R. Hunt, with the Grand Forks center. Hunt
and research associate James H. Swain recently studied the bioavailability
to rats of six commonly used elemental iron powders. They found that
the ability of these powders to treat iron deficiency anemia in rats
ranged from only 21 to 64 percent of that of ferrous sulfate. Moreover,
bioavailability among the six powders differed significantly.
That preliminary animal study helped the scientists select
which powders to pursue for further study in humans. "In our upcoming
study," says Hunt, "we'll test the iron status in four groups
of women volunteers with low iron stores. Two groups will be fed rolls
fortified with two different iron powders; another group will be fed
rolls with placebo; and the final group will be fed rolls fortified
with ferrous sulfate." The scientists will determine the ability
of the test powders to improve the volunteers' iron status.
"We'll also look at the effects of different enhancers
and inhibitors of iron absorption," says Hunt. For instance, vitamin
C is known to enhance iron absorption from foods. The scientists want
to know if vitamin C enhances iron absorption from the powders to the
same extent. But phytic acid, which occurs naturally in whole grains
and legumes, inhibits iron absorption from food. The scientists will
test whether phytic acid inhibits absorption of iron from the iron powders
to the same extent.—By Rosalie Marion Bliss,
Agricultural Research Service Information Staff.
This research is part of Human Nutrition, an ARS National
Program (#107) described on the World Wide Web at www.nps.ars.usda.gov.
Janet Ross
Hunt is with the USDA-ARS Grand
Forks Human Nutrition Research Center, 2420 2nd Ave., Grand Forks,
ND 58202; phone (701) 795-8328, fax (701) 795-8220.
"Testing the Fortitude of Iron in Cereals" was published
in the May
2003 issue of Agricultural Research magazine.
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