Calcium supplements and the danger of lead

Science News, Sept 4, 1993 by Kathy A. Fackelmann

Warning: Calcium supplements may be hazardous to your health. That advisory may not appear on the package label, but it's the conclusion reached in a new study that looked for lead contamination in these dietary preparations.

Lots of Americans take extra calcium, which is sold in a range of forms, including tablets, bonemeal, and liquids. This dietary additive is popular because evidence shows it wards off a variety of ills, including osteoporosis, a bone-thinning disease that strikes older women.

Adults aren't the only ones who rely on this mineral. A report in the Aug. 18 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION shows that 12-year-old girls who take calcium tablets for 18 months build more bone mass than those who don't, a possible hedge against osteoporosis later in life. That conclusion has spurred some experts to advise girls to take calcium supplements or drink calcium-fortified juices.

Furthermore, calcium supplements are given to toddlers and young children who are allergic to or have difficulty digesting calcium-rich dairy products, such as milk and cheese.

Yet some calcium supplements contain lead. For children, even small amounts of this poisonous metal can be detrimental, leading to diminished IQ and stunted growth (SN: 1/27/90, p.63; 9/21/91, p.189). Indeed, more than 10 years ago the Food and Drug Administration (FDA) warned about the dangers of excess lead in certain forms of calcium supplements, particularly bonemeal, which is made from pulverized animal bones.

A study in the August AMERICAN JOURNAL OF PUBLIC HEALTH suggests that lead in calcium supplements remains a public health threat.

Bernard P. Bourgoin of the National Water Research Institute in Burlington, Ontario, Alfredo J. Quattrone, a Toxicologist with the California Department of Health Services in Sacramento, and their colleagues analyzed 70 brands of calcium supplements sold in the United States and Canada. They grouped the supplements into five categories: dolomite, a chalky compound often derived from petrified mollusk shells; bonemeal; refined and natural-source calcium carbonate; and calcium chelates, which include the calcium added to fruit juices.

The amount of lead present in the products ranged widely, the team found. Of the 70 products they studied, 17 (24 percent) exceeded the FDA's limit of 6 micrograms of lead per day for children age 6 and younger. And that's the total lead that can be safely ingested from all sources, not just a calcium tablet, Quattrone notes. Fewer than 20 percent of the products had concentrations of lead equal to or lower than those found in cow's milk, the researchers discovered.

How can the average consumer find a lead-free calcium supplement? Right now, that's a tough task, admits FDA toxicologist Michael Bolger, who points out that the agency has no standards for lead in food supplements. However, FDA does plan to regulate the lead content of these supplements in the future, he says.

Until then, Quattrone points out, consumers can avoid bonemeal, the worst offender in their study. Particularly alarming, he notes, is that people often ingest more than the recommended amount of this form of calcium.

As for tablet or liquid forms, Quattrone says that preparations with the USP (United States Pharmacopeia) seal of approval are purified by the manufacturer. Products that meet these voluntary standards are less likely to contain high concentrations of lead or other contaminants.

For people who want extra calcium without the worry, there's always the time-honored approach of adding more calcium-rich foods to the diet, Bolger points out. For those who can't eat dairy products, that means generous portions of foods high in calcium, such as kale and broccoli.