NEW YORK (Reuters Health) - Iron deficiency, even to a moderate degree, can hinder women's memory and learning - but iron supplements can turn those problems around, a study has found.

Iron is essential for delivering oxygen to cells throughout the body, and iron deficiency is known to impair brain development and learning in babies and children. But women of childbearing age are also at elevated risk of low iron stores, and less is known about the possible cognitive effects in them.

In the new study, researchers at Penn State University found that women with even moderate iron deficiency - not severe enough to diagnose full-blown anemia - scored more poorly on tests of memory, attention and learning than women with sufficient iron levels. Those with anemia had the worst scores.

After 4 months on iron supplements, however, women who'd been deficient in the mineral showed an improvement in their mental acuity. Those who had a significant rise in an iron-storing protein called ferritin also improved their test performance by 5 to 7 times.

The findings are published in the American Journal of Clinical Nutrition. Dr. Laura E. Murray-Kolb, who is now based at Johns Hopkins University in Baltimore, led the study.

"Our data are significant in that they show that normalization of iron status affects mental functioning in otherwise healthy adult women," Murray-Kolb and colleague Dr. John L. Beard write.

The findings, they add, show that the effects of iron deficiency are not limited to the developing brain. Moreover, they challenge the traditional belief that iron deficiency causes no apparent problems until it progresses to full-blown anemia, the researchers write.

The study included 113 women ages 18 to 35 given standard tests of memory, attention and learning. At the outset, blood tests showed that 42 women had sufficient iron levels, while the rest had either iron deficiency or overt iron-deficiency anemia.

The women were then randomly assigned to take either iron supplements or inactive pills for 16 weeks, before taking the cognitive tests again. Among women who were iron-deficient at the start, those whose iron stores increased significantly made far greater improvements in their test scores, the researchers found.

They say the results point to a need for better detection of people at risk of cognitive deficits due to iron deficiency.

Among women, those who are pregnant or have heavy menstrual periods are among the most at risk of iron deficiency if they don't get enough from food or supplements.

The recommended iron intake for women ages 19 to 50 is 18 milligrams (mg) per day, and 27 mg during pregnancy. Food sources of iron include meat, poultry, beans, spinach and fortified cereals.