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Zinc and Iron Interplay Explored

Puzzling interactions of two essential nutrients--zinc and iron--are the focus of experiments by Agricultural Research Service scientists at Davis, Calif. Their studies may help explain why, for some pregnant women, taking prenatal iron supplements interferes with benefits from zinc.

Janet C. King, director of the ARS Western Human Nutrition Research Center at Davis, is collaborating in the study with Concepcion Mendoza, a post-doctoral scientist in King's laboratory. Fernando E. Viteri of the University of California at Berkeley is a co-investigator.

In an earlier study of zinc, King and others tested 13 pregnant volunteers, aged 18 to 40. The researchers followed the volunteers' uptake and use of zinc from food. They tracked the volunteers from the beginning of pregnancy through the first 3 months of breast-feeding. Four of these volunteers, on their doctors' orders, took a daily iron supplement.

Previous studies, done elsewhere, showed that zinc absorption in rats increased during lactation. In the human study, King and colleagues found that all of the volunteers, except the four who took iron supplements, increased their zinc absorption during breast-feeding.

Now King, Mendoza and Viteri are building upon this previous work in an ongoing experiment with pregnant volunteers, aged 22 to 40. The researchers want to determine whether zinc levels are affected by taking iron supplements at a particular time of day, or with or without a meal.

To find that out, the scientists are providing zinc supplements to all of the volunteers to take every day. Some of the women are also taking iron supplements daily, either in the morning with their breakfast or at bedtime.

Zinc likely affects every general function in the human body. It is an important part of many enzymes needed for healthy skin and for the immune, nervous and digestive systems to work properly. Foods that are good sources of zinc include beans, whole grains, shellfish, red meat and dark-meat poultry.

For more information about this zinc and iron research, see the Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.