Inulin May Help With Iron Uptake, Too
Chalk up another potential health benefit for inulin,
a plant compound used in many foods that’s already been credited with
boosting gut and colonic health and helping the body absorb dietary
calcium.
Swine research funded in part by the Agricultural Research Service
has found that this nondigestible carbohydrate—which reaches the colon
intact, where it’s metabolized by beneficial bacteria—may help people
absorb more iron from staple food plants that are rich in compounds
that hamper iron uptake.
Iron is needed to form hemoglobin, which transports oxygen in the blood.
In Ithaca, New York, ARS plant physiologist Ross Welch,
of the U.S. Plant, Soil, and Nutrition Laboratory, and Cornell
University scientists Koji Yasuda, Karl R. Roneker, Xingen Lei, and
Dennis D. Miller showed that young pigs fed corn- and soy-based diets
supplemented with inulin absorbed more iron from their feed than pigs
fed the same diet without inulin.
Welch says the discovery may prove significant in the
worldwide fight against iron deficiency. “Without inulin, the colon
absorbs very little iron from staple plant-based foods such as soybeans
and corn because they contain high amounts of phytic acid that inhibit
iron absorption.”
Young pigs were used, says Welch, because “They’re an
excellent model for studying human iron nutrition. Their
gastrointestinal tract anatomy and digestive physiology are very
similar to those in humans.”
The scientists conducted two experiments, one with 24
weanling pigs over 5 weeks and one with 12 pigs over 6 weeks. The pigs
were fed either a corn- and soy-based diet low in iron or the same diet
supplemented so that 2 or 4 percent of it was composed of purified
inulin.
“At 4 percent is where we saw a significant effect of
inulin on iron absorption,” says Welch. “Pigs fed the 4-percent inulin
diet showed a 28-percent improvement in absorbable iron and a
15-percent improvement in final blood hemoglobin concentration over
those not fed inulin.
“Also, pigs fed the 4-percent-inulin diet were found to
have higher soluble iron concentrations in the proximal, mid, and
distal colon.”
Welch says that interlaced processes may explain why
inulin boosts iron absorption during digestion: “The beneficial
bacteria that ferment inulin in the colon release short-chain fatty
acids that increase digestive acidity, and that causes mucosal cells to
proliferate. This produces more cell surfaces where iron absorption
takes place.”
He adds that within these gut mucosal cells, metabolic products from inulin fermentation also activate a gene—Divalent Metal Transporter 1, or DMT1—that’s responsible for a protein required for iron uptake by these cells.
The main source of inulin in the U.S. diet is wheat,
although Welch says that onions and garlic are among the richest
sources. Later studies will focus on breeding staple food crops with
enhanced inulin levels.
In addition to ARS, the study was funded by the global
HarvestPlus program, which is administered by the International Food
Policy Research Institute in Washington, D.C., and the Colombia-based
International Center for Tropical Agriculture.—By Luis Pons, formerly with ARS.
This research is part of Human Nutrition, an ARS national program (#107) described on the World Wide Web at www.nps.ars.usda.gov.
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
is with the USDA-ARS U.S. Plant, Soil, and Nutrition Research Laboratory, Tower Rd., Ithaca, NY 14853-2901; phone (607) 255-2434, fax (607) 255-1132.
"Inulin May Help With Iron Uptake, Too" was published in the January 2008 issue of Agricultural Research magazine.
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