Calcium Supplementation May Benefit Lead Levels - JAMA Editorial

Calcium intake impedes lead absorption and stops the body from accessing lead deposits in bones, Robert Heaney, MD, maintains in an editorial response to a study on lead content in calcium supplements.

Small quantities of lead can be considered safe when they come from high-calcium sources such as supple-ments because "calcium both blocks intestinal lead absorption and reduces access to endogenous lead deposits," the Creighton University researcher writes in the Sept. 20 Journal of the American Medical Association.

Heaney's editorial responds to a study appearing in the same issue of JAMA conducted by Edward Ross, MD, University of Florida, et al., that found four of seven natural calcium supplements and four of 14 refined calcium supplements from major suppliers contained measurable amounts of lead.

Heaney notes that in the study, Ross et al. do not mention "the remarkable extent to which the supplement industry has reduced the lead content of the calcium supplements now on the U.S. market."

He points out that while a 1993 study found measur-able lead in "most of the 70 brands of supplements" tested, in comparison, "lead content was below the detection limit in two-thirds of the 22 products" in the Florida study.

Again referring to calcium's tendency to block lead absorption, Heaney notes the researchers also "do not report measurements of blood lead in persons taking supplements, nor is it likely that, if they had made the measurements, they would find the hazard to which they wish to draw clinicians' attention."

"There is, actually, more reason to be concerned about alarming the public unnecessarily," he contends. "A backlash against calcium supplements...would unquestionably do far more harm, for health generally and for lead poisoning specifically, than would continued ingestion of current supplements."

The study, which examined lead content of calcium supplements, was performed because "the medical community now more vocally advocates increasing [calcium] intake (typically in the form of supplements) to prevent or treat osteoporosis, we thought it important to reexamine the issue," Ross et al. note.

Twenty-one nonprescription calcium carbonate products were selected for the study. Seven were considered "natural source," coming from oyster shell, and 14 were designated as refined. One Rx product and one synthetic non-calcium product also were studied.

Lead analysis was performed using electrothermal atomic absorption spectrometry with Zeeman background correction. The researchers looked at recommended dosages for children, osteoporosis and phosphate binding in dialysis patients. The content goal for supplements was set at 1 mcg per day of lead with the absolute limit set at 6 mcg/d.

The study found eight of 21 calcium carbonate preparations had measurable lead content. Natural source products were found to yield approximately 0.9 to 1 mcg/d of lead for every 800 mg/d of calcium, the recommended childhood daily allowance.

Four refined calcium supplements contained 1 to 1.8 mcg/d of lead at childhood doses. Ross et al. note that at higher doses - either for osteoporosis treatment or for renal disease - calcium intake, and therefore lead intake, would be higher.

As a result of their findings, the researchers conclude calcium supplements "may pose an easily avoidable public health concern."

Responding to the study and editorial, the Council for Responsible Nutrition highlighted the fact that "13 of 21 calcium supplements had no detectable levels of lead." The group also pointed to Heaney's observation that a small meal with salad and wine contains 10 to 50 times more lead than a calcium supplement.

"This study should not be interpreted as cause for alarm by consumers," the National Nutritional Foods Association commented.

Independent testing group ConsumerLab.com recently reported that of 35 calcium products tested - including antacids, tablets and juices - none contained more than 1 mcg of lead per gram of calcium (¹ (Also see "ConsumerLab.com Calcium Testing Uncovers USP Label Misuse" - Pink Sheet, 11 Sep, 2000.)).

In September 1999, FDA decided not to adopt new lead limits for calcium-containing supplements, although the agency said it was investigating the possibility of working with the U.S. Pharmacopeia to establish a lower standard (² (Also see "Lower Lead Limits For Calcium-Containing Products Shelved By FDA" - Pink Sheet, 25 Oct, 1999.)).