Do Your Genes Make You Absorb Too Much
You probably know that iron deficiency may lead to anemia. But did you also
know that some people absorb too much irondue to a condition known as hemochromatosis?
ARS nutrition studies show that people with hemochromatosis,
a genetic condition that causes them to absorb and accumulate too much
iron, need not worry about absorbing too much of this nutrient from iron-fortified
Hemochromatosis is an inherited genetic disorder that results in excessive
iron absorption and accumulation. Over time, the build-up of iron in vital organs
makes people sick and more susceptible to cancer, diabetes, and liver failure.
An estimated 1 of every 200 to 500 people in the United States has genes that
can lead to increased iron accumulation, and about 1 percent of those eventually
develop symptoms of hemochromatosis. Geneticists characterize these people as
homozygous because they carry two copies of the altered or mutated
geneone from each parent.
But what about people who carry only one copy of the altered gene? This is
surprisingly common, occurring in an estimated 1 of every 10 people in the United
States, especially those of Northern European origin.
Nutritionist Janet R. Hunt and molecular biologist Huawei Zeng, with the ARS
Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota, have
conducted studies to determine whether individuals with only one copy of this
genetic mutation could also be at risk of absorbing too much iron.
Those who carry one normal gene from one parent and one mutated gene from the
other parent are heterozygous and are often called carriers.
Thats because even though their one normal gene protects them from getting
hemochromatosis, they can pass the mutation on to their offspring.
Hunt, who heads the centers Micronutrient Absorption and Metabolism Unit,
collaborated with Zeng to determine whether carriers also absorb more iron than
usual. If so, then the common practice of fortifying foods with iron could
pose a health risk for them, says Hunt.
For this genotyping study, Hunt and Zeng tested 359 volunteers by taking DNA
samples either from the inside of their cheeks or from blood. Those identified
as carriers had their iron absorption measured from regular and iron-fortified
meals. Carriers of the mutation did not absorb iron differently than volunteers
without the mutation, whether or not the meal was iron fortified. This was true
for both forms of iron commonly found in foods: heme iron, from
meat, poultry, or fish; and nonheme iron, found in plant foods as
well as animal foods.
The researchers determined that carriers of this particular DNA mutation dont
need to worry about absorbing too much iron. The study supports public
health policies that allow addition of iron to foods to help those at the other
end of the scale, who may be at risk of too little iron, says Hunt.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.
"Do Your Genes MakeYou Absorb Too Much Iron?" was published
in the May 2005
issue of Agricultural Research magazine.