Sept. 19, 2000 -- From women trying to reduce their risk of osteoporosis to children who are lactose intolerant, millions of people take calcium supplements every day, and most assume they're safe and healthy.
That's why the findings of a new study may come as a surprise to many people. The study, of calcium supplements available from national chain pharmacies and discount stores, indicates that some contain enough lead to be dangerous if the supplements are taken in high doses, researchers say.
That doesn't necessarily mean you should stop taking your supplement. For most people, the amounts of lead found in the supplements are not harmful, and one expert notes that lead is found naturally in many foods. Still, if you're taking high doses of calcium, you might want to ask a doctor or pharmacist about your supplement's safety.
Researchers have known for decades that most calcium supplements contain some lead, says Edward A. Ross, MD, author of the study published in the Journal of the American Medical Association. Some, but not all, of these supplements are made from oyster shells, which contain lead that is generally removed in the manufacturing process. Ross is director of the end-stage renal disease program at the University of Florida in Gainesville.
In his study of 21 over-the-counter calcium supplements and two prescription formulations, Ross found that approximately one-third contained measurable lead. Makers of supplements are not required to list lead content on their labels, but some are marketed as being "essentially lead-free." In the study, two supplements that made that claim had no measurable lead content.
Of the better-known brands, both Tums Ultra and Tums EX calcium-containing antacids had levels of lead that were too low to measure by the study's standards, but Caltrate and one Eckerd brand of calcium supplements contained levels of lead that Ross estimates could exceed safe limits if taken at doses commonly prescribed for the prevention of osteoporosis.
"The labels don't help you at all," Ross says. "You might get lucky and find one that is essentially lead-free, but there is no uniform regulation for the labeling." Because of that, he says, consumers can't assume that name brands are better than lesser-known names or, for that matter, that all chain pharmacy brands are alike. Although one of three Eckerd brand supplements tested high, for instance, two Walgreens brand supplements had lead levels that were too low to measure.
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.