By Anne Harding
Taking calcium supplements during pregnancy reduces a woman's blood levels of lead, and thus the danger that her foetus will be exposed to the toxic metal, new research conducted in Mexico shows.
"You could actually see the more a person took, the more their blood levels went down," Dr. Adrienne S. Ettinger of the Harvard School of Public Health in Boston, who helped conduct the study, told Reuters Health.
During pregnancy, women need more calcium to help build foetal bones, and their bodies may boost reabsorption of their own bone tissue to get it. This in turn can cause any lead stored in the bones to enter the blood circulation, exposing the foetus to lead, which can impair neurological development and cause lasting damage to the brain.
There is evidence that calcium can help prevent the release of lead from the bones, Ettinger and her team note in their report in Environmental Health Perspectives. The researchers previously found that lactating women who took calcium supplements had significantly less lead in their blood and breast milk.
To investigate the effects of calcium supplementation during pregnancy, "the period of greater relevance for maternal-foetal transfer of lead," they randomly assigned 670 pregnant women to take 1 200 mg of calcium daily or a placebo. Thirty-five percent of the study participants said they used lead-glazed pottery to serve, store or prepare food.
Blood lead levels fell by 11 percent, on average, in women who took calcium. Women who consumed the most had the most benefit; those who took 75 percent or more of the recommended number of calcium pills had a 24-percent drop in blood lead.
Women who started out with the most lead in their blood had an average 17-percent reduction in blood lead levels. For women with high initial blood lead levels who also reported using lead-glazed pottery, calcium reduced lead levels by 31 percent.
The US phased out leaded petrol in the early 1970s, so the great majority of reproductive-age women in this country don't have significant amounts of lead in their bones, Ettinger said in an interview. But those working in battery manufacturing, mining or other occupations involving lead exposure are still at risk, she added.
"It's not a lot of women, but the women who are exposed occupationally could be very highly exposed," the researcher said. Women in many parts of the developing world, where leaded gas is still in use or was only recently phased out and occupational and household exposure to lead tends to be more common, are also at risk, according to Ettinger.
The reduction in blood lead levels she and her colleagues saw were relatively modest, the researcher noted. "We're not suggesting that people just take a pill and think everything is fine," she said. "In addition to decreasing exposure sources this may be an important preventive method."
Women in the US are typically instructed to take prenatal vitamins, but their calcium content varies widely, she added. "I think it's important to be aware of how much you're getting with the supplement and figure out with your doctor if you have risk factors for lead, and if so maybe additional calcium would be necessary," Ettinger advised.