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NEW YORK (Reuters Health) - Taking iron supplements doesn't benefit pregnant women who don't already have iron-poor blood, a new study finds.
Anemic pregnant women in western Africa boosted their iron levels by taking supplements, but the women who had higher levels to begin with didn't see any extra increase, according to the study in the American Journal of Clinical Nutrition.
"This is what you would expect based on how the gut responds to iron," said Kimberly O'Brien, professor of human nutrition at Cornell University, who was not involved in the study. "The gut senses when you need that iron," and your body absorbs it better, O'Brien told Reuters Health.
Iron is essential to making hemoglobin, the component of red blood cells that carries oxygen throughout the body. In pregnancy, a woman's iron needs rise as her body produces greater volumes of blood.
Fewer than one in five pregnant women in the U.S. were anemic in 2005, according to the World Health Organization (WHO). In Africa, however, up to 57 percent of pregnant women are anemic.
To determine how much supplemental iron was needed to bring women's levels up to a healthy range, the team of Belgian and U.S. researchers recruited 1,270 pregnant women in Burkina Faso. About 550 of them (43 percent) were anemic at the beginning of the trial.
Half the women took supplements with 60 milligrams of iron and 400 micrograms of folic acid. The other half took supplements with 30 milligrams of iron, the same amount of folic acid, and several other nutrients including zinc and vitamins A and C. Both groups took the vitamins from the time they were enrolled in the trial until 3 months after delivery.
The researchers found that women who were anemic at the beginning of the study and those who weren't ended up with about the same levels of iron in their blood -- around 11 grams per deciliter. Levels slightly above this are considered normal in pregnant women by the WHO.
The women who took iron and folic acid plus other nutrients had the same benefit as the women who took supplements with only iron and folic acid, even though the latter contained twice the amount of iron. This may be because the women absorb enough iron even at the smaller dose, O'Brien said.
Iron during pregnancy is important because the fetus needs oxygen to develop properly (see Reuters Health story of March 3, 2011). Low maternal iron levels have been linked with low birth weight, which is dangerous for babies, because they're more likely to have disabilities or die during before they're a year old.
Iron levels in pregnant women actually drop as the pregnancy goes on, with iron needs the highest in the third trimester, O'Brien said.
U.S. guidelines recommend that pregnant women get 27 milligrams of iron a day from a combination of food and supplements. Most prenatal vitamins contain at least 18 milligrams of iron, and cost between $3 and $40 a month. Women of childbearing age typically get about 13.7 milligrams of iron a day, according to the Centers for Disease Control and Prevention.
The current study's lead author, from the Institute of Tropical Medicine in Antwerp, Belgium, did not respond to requests for comment by deadline.
"The benefit of iron supplements in nonanemic women is unclear," the team concludes in their paper.
Women in Africa may get less iron in their diets than those in the U.S., O'Brien noted. Plus more people there have intestinal parasites, which "hook onto your gut and feed on blood," she said.
They may "have a greater iron need to offset blood loss to those parasites," she explained.
When the body has sufficient iron levels, the gut will not absorb any more, O'Brien added. "Normally that's okay because we have sufficient stores, but iron demands of pregnancy are so high."
SOURCE: bit.ly/hxQQpz The American Journal of Clinical Nutrition, online March 2, 2011.