Excess Iron Throws Out Welcome Mat to Bacteria

Heart, liver, intestines may suffer from over-fortified diet

FRIDAY, Nov. 2, 2001 (HealthDayNews) -- Too much iron in the diet could be making people more susceptible to intestinal infections, claims a new study.

And that puts into question whether U.S. food makers need to fortify foods with iron, says one of the nutritionists who conducted the research.

The body needs a certain amount of iron to survive, but excessive amounts of the mineral can increase the risk of heart disease, affect the immune system and damage the liver over time, as well as make people more receptive to intestinal bacteria like those that cause food poisoning, the study says.

Researchers at Ohio State University examined human cells that were given too much iron and then exposed to the bacteria Salmonella enteritidis. The bacteria had an easier time entering cells with a high iron content and survived in greater numbers in high-iron cells, the study says.

"Our results showed that the invasion and survival of the bacteria increased," says Mark Failla, a nutrition professor at Ohio State.

Cells high in iron also seemed to have an overactive immune response, which could lead to inflammation of the intestine, he says. Details appeared in the Journal of Nutrition earlier this year.

Though the research so far has involved human cells only in a laboratory setting, Failla says the findings suggest that the practice of routinely fortifying foods with iron to combat iron deficiency might be causing health problems in countries like the United States, where iron deficiency generally is not a problem.

Failla says, "I don't necessarily support iron fortification of the food supply. It would be more appropriate to test the iron status of individuals and supplement when necessary." But such a change would be expensive to carry out, he says.

Samantha Heller, a senior clinical nutritionist at New York University Medical Center, says foods aren't fortified just for American consumers, but are exported to countries where iron deficiency is common. The World Health Organization says up to 5 billion people worldwide suffer from iron deficiency.

It's too soon to draw any conclusions from the study, Heller says.

"This is a study that looked at cells. We don't know to what extent we can extrapolate this information. In the body, results could be different," she says. Also, she says no one knows how common excess iron levels are.

What To Do

Too little iron can cause cognitive development problems in children and impair work performance and motor abilities in adults. Too much iron also can cause health problems, so it's important to check with your doctor if you suspect either case.

Neither Heller nor Failla recommends taking iron supplements unless your doctor prescribes them, though Heller says the amount contained in most multivitamins probably is OK for the average person.

To learn more about the effects of too much iron, go to the U.S. Office of Dietary Supplements. For more information on iron in the diet generally, read this article from the British Nutrition Foundation.

SOURCES: Interviews with Mark Failla, Ph.D., professor of nutrition, Ohio State University, Columbus; Samantha Heller, M.S., R.D., senior clinical nutritionist, New York University Medical Center, New York City; May 2001 Journal of Nutrition
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