Ross says the levels of lead found in the supplements are not dangerous for most people, but he is concerned about patients with kidney disease who must take high doses of calcium. Other people potentially at risk are postmenopausal women taking high doses of the supplements to prevent osteoporosis as they age, and children and adults with lactose intolerance who can't get adequate calcium in their diet from dairy products. Lead is particularly dangerous for children. Exposure to lead, in the form of paint and dust, has been associated with learning problems and lowered IQ in young children.
But another expert says the amount of lead in the calcium supplements is "negligible."
The researchers estimated the levels of lead that would be found in the blood of people taking the various supplements, but they didn't actually test anyone's blood to see if their estimations were correct, says Robert P. Heaney, MD, who is a consultant for many of the major calcium suppliers in the U.S.
Heaney, a professor of medicine at Creighton University in Omaha, says people taking calcium supplements should not be overly alarmed by the study and should not stop taking the supplements. Both he and Ross say people concerned about lead content should talk to their doctor or pharmacist about which supplement might be best. If you take large quantities of calcium, both experts say looking for the "essentially lead-free" claim on the label is not a bad idea.
"Bear in mind that milk contains some lead because cows graze on grass," Heaney says. Other foods naturally high in lead include grapes, raisins, berries, wine, salad greens, and alfalfa sprouts. All of these items get their lead from the soil in which they are grown, and the lead content of soil can vary greatly.
Heaney says calcium actually prevents lead from being absorbed, and in that sense, supplements, even if they contain some lead, actually may be protective against some of the lead we encounter in food.