CHAPEL HILL -- Pregnant women who don't consume enough calcium in their diets or through supplements show greater increases in lead in their bloodstreams than pregnant women with normal calcium levels, according to a new University of North Carolina at Chapel Hill study.
That is because 95 percent of the body's lead is contained in bone tissue, which, in pregnant women getting less calcium turns over, or "demineralizes," more rapidly than bone in other pregnant women and releases locked-up lead into the blood, researchers found.
Lead emerges from bone during the second half of pregnancy and might hurt both mothers and their babies, their work showed. The study also offers new evidence that calcium consumption can minimize bone demineralization in pregnant women.
"Past research has linked lead to many adverse conditions, including nervous system and possible cardiovascular problems," said Dr. Irva Hertz-Picciotto, professor of epidemiology at the UNC-CH School of Public Health and lead author. "In this study, in which lead levels were very low overall, we saw that the same characteristics that predict greater lead at high exposures also predict a greater lead level even at a much lower range. That means there may be virtually no 'natural' background of blood lead for which man-made sources can't be identified."
Those characteristics, or variables, that correspond with more lead include smoking, less education, being black and low calcium intake, she said. Variables associated with a reduced lead level include history of breastfeeding and higher calcium intake.
"We are still trying to determine whether there are health effects from these low levels," Hertz-Picciotto said.
A report on the findings appears in the November issue of the Journal of Epidemiology. Co-authors are Margaret Schramm and Dr. Margaret Watt-Morse of Magee-Women's Hospital at the University of Pittsburgh, Kim Chantala of UNC-CH's Carolina Population Center, Dr. John A
Contact: David Williamson
University of North Carolina at Chapel Hill