Low Calcium May Equal High Lead Levels in Pregnant Women

Nov. 8, 2000 -- Most pregnant women pay close attention to nutrition. But one thing they may not be aware of is the link between calcium intake and lead. New research suggests that not getting enough calcium during this critical time can drive up levels of lead in the blood, which could be harmful to a developing baby.

Lead in a mother's blood may affect the development of various organs of the fetus, including the brain. In children, lead exposure has been linked to learning and intelligence problems.

During pregnancy, when the body's demand for calcium is high, not getting enough of the crucial mineral speeds up the production of new bone to replace old, dying bone. Because nearly all of the body's lead is stored away in bone, the lead "leaks" into the bloodstream when the bone turns over. It's a process that calcium can help prevent.

A study in the November issue of the American Journal of Epidemiology finds that women with the lowest levels of calcium -- gotten from either food or supplements -- also had the highest levels of lead in the blood. Although the study did not show any direct health impact on the fetus, the researchers say it's reasonable to assume that any amount of lead in the body would be potentially dangerous.

The study involved almost 200 pregnant women who had their blood drawn and tested for lead up to five times during their pregnancy. The women also reported on the amount of calcium in their diet from foods including milk, yogurt, cheese, ice cream, eggs, pizza, and fish.

"Definitely, the women who were getting very little calcium were at risk for higher blood lead levels," says lead author Irva Hertz-Picciotto, MD, of the University of North Carolina at Chapel Hill. She says most of the women in the study reported getting the bulk of their daily calcium from milk and cheese pizza. Other common sources included vitamins and antacids.

In addition, black women had lower calcium intake and higher blood lead levels than white women, and smokers had lower calcium and higher lead than nonsmokers.

Hertz-Picciotto says the study suggests that women need to be getting above and beyond the recommended daily allowance of calcium during pregnancy to avoid rising lead levels. She says pregnant women should aim for a minimum of 2,000 mg of calcium per day, which is about 800 mg higher than current government recommendations.

Furthermore, women who get little calcium early in pregnancy may benefit from calcium supplements in addition to bulking up their diet with extra glasses of milk and other calcium-rich foods.

In the study, lead increased with each trimester due to the increasing demands on the body for calcium during pregnancy. Lead levels also increased with age.

A researcher who studies lead tells WebMD that the study is a practical reminder for women to pay particular attention to calcium when they're pregnant and make sure that they are meeting -- and exceeding -- the recommended amounts.

In addition, Howard Hu, MD, MPH, ScD, says women who think they have had lead exposures from work or other environmental sources like lead paint should consider seeing a specialist and have their blood lead levels tested.

But Hu, an associate professor of occupational medicine at the Harvard School of Public Health in Boston, says that much more research is needed to determine how much of a problem low calcium and increased lead in the blood may be. To answer that question, his research group is planning to give calcium supplements to pregnant women to see if it makes a difference in their blood lead levels.