Healthnotes Newswire (September 21, 2000)—A new study in yesterday’s Journal of the American Medical Association (JAMA) has found that a majority of calcium supplements sampled contained no detectable levels of lead.¹

Of the 21 over-the-counter calcium supplements tested in the study reported in JAMA, 13 had no detectable levels of lead. Of those that did contain measurable lead, none exceeded the Food and Drug Administration’s (FDA) maximum tolerable exposure levels,² and two-thirds contained less than the much more stringent standards put forth in California’s Proposition 65.³ This represents a sharp decline in lead content of calcium supplements since 1993. In that year, a survey of 70 brands of calcium revealed that about 25% of products exceeded the FDA’s allowable limits.⁴

A cause for alarm or celebration?

The presence of any amount of lead in calcium supplements may come as an unwelcome surprise to consumers. Lead is a heavy metal that stunts growth in children, damages the kidneys and brain, causes anemia, and lacks any beneficial impact on human health. So what is it doing in dietary supplements? The marine sources of calcium (oyster shells) almost invariably contain some lead. It is expensive to remove it, although an increasing number of manufacturers are doing just that, using a chemical process.

Fortunately, the very low levels of lead found in the JAMA study suggest that the dietary supplement industry has made considerable progress in the last decade. The benefits of calcium supplementation, which include prevention of osteoporosis and certain cancers, now outweigh the theoretical concern about the low levels of lead found in this study.

Even the calcium supplements that were found to contain residual lead in the JAMA study had far less lead than is typically consumed in food. In an editorial accompanying the JAMA article, calcium authority Robert P. Heaney, MD, stated, “a luncheon of mixed salad greens and a glass of Chardonnay will contain 10 to more than 50 times as much lead as could be ingested in a typical calcium supplement tablet.”⁵ Research on average U.S. dietary intake of lead from various foods and beverages corroborates Heaney’s statement: lead consumption from food and beverages far exceeds that obtainable from the calcium supplements considered in the present study.^{6 7}

How much is too much?

The authors of the JAMA study, Edward A. Ross, MD, and colleagues, question whether there can be any allowable amount of lead in supplements, since no risk-free blood level has ever been established.^{8 9} Regrettably, since the advent of metallurgy, the mining of lead for industry, ammunition, crystal, and, until recently, paint and automotive fuels, has made residual environmental lead a fact of life. Efforts to minimize lead exposure are best targeted at major sources; calcium supplements are, at worst, sources of only trivial amounts of lead. As Dr. Heaney points out in his editorial,“A backlash against calcium supplements—evoked by a lead scare—would unquestionably do far more harm, for health generally and for lead poisoning specifically, than would continued ingestion of current supplements.” Calcium supplements are a leading recommendation for the prevention of osteoporosis, or brittle bones.

“If there is any place in the food chain in which small quantities of lead may be safe,” Heaney continues, “it is in sources with high calcium content.” This is because calcium may decrease the absorption of lead, if it is ingested concurrently. However, this is a point of contention. Dr. Ross and colleagues insist that the ability of calcium to attenuate the absorption of lead has not been confirmed. And they are not entirely wrong. While preliminary research suggests a protective effect of calcium against lead absorption,^{10 11 12 13 14} other research has failed to confirm such an effect.^{15 16 17} Nevertheless, Ross and colleagues did not report measurements of blood lead in persons taking calcium supplements, so their data offer no direct evidence of harm. Previous reports addressing this issue have found that blood lead levels decrease as calcium intake increases, suggesting a protective rather than a harmful effect.^{18 19}

Who is at risk?

People on kidney dialysis (who must take extremely large amounts of calcium) are the only group of people likely to ingest unsafe levels of lead from current calcium supplements. For these individuals, it is recommended that calcium supplements labeled “lead-free” be used. The two calcium supplements in the study that were labeled “lead-free” had no detectable lead. However, this was also true of several calcium supplements that were not specially labeled.

As it turns out, the principal sources of lead for the average North American adult, particularly elderly adults, are not their supplements but their own skeletons. After a lifetime of exposure, lead is stored in the bones. When the body requires additional calcium, if it is not taken as a supplement or in food, the body will release stored calcium from the bones into the blood—and with it stores of accumulated lead.

Some researchers have advocated for widespread calcium supplementation simply as a way of keeping bone lead locked up where it will do the least harm.²⁰ Heaney argues that the small amount of lead in calcium supplements is less likely to be taken up into vulnerable tissues (like the brain) because the calcium in the supplement decreases its absorption. If older adults were to avoid calcium supplements, Heaney predicts their blood lead levels would actually increase because of increased absorption of lead from dietary sources and increased release of lead sequestered in the bone.

In the final analysis, the concern about lead in calcium supplements may be much ado about nothing. Calcium supplements contribute only a small fraction of the total daily lead intake, and most of that lead is probably not absorbed. Even the authors of the JAMA study acknowledge that the risk of clinically significant lead exposure from calcium supplements is “small.” They do, however, correctly identify a need for self-regulation among dietary supplement manufacturers to reduce lead in calcium supplements to the lowest levels attainable.

In the present study, low levels of lead were detected in the following calcium carbonate products (in order of decreasing content): Caltrate 600 (Caltrate; Pearl River, NY); Calcium, 600 mg (Eckerd; Clearwater, FL); Oyster Shell Calcium, 500 mg with Vitamin D (Nature Made; Mission Hills, CA); Liqui-Cal Calcium 600 softgels (Advanced Nutritional Technology; Dublin, CA); Calci-Mix (R & D Laboratories; Marina del Rey, CA); Natural Oyster Shell Calcium, 500 mg with Vitamin D (Spring Valley; Allegan, MI); Hi-Calcium from oyster shell (Eckerd; Clearwater, FL); and Oscal 500 (Oscal; Pittsburgh, PA).

The following calcium carbonate products (listed alphabetically) contained no detectable lead: Calci-Chew (R & D Laboratories; Marina del Rey, CA); Calcium, 600 mg plus vitamin D (Sundown; Boca Raton, FL); Calcium, 600-mg supplement (Nature Made; Mission Hills, CA); Chewable Ultra Antacid (Eckerd; Clearwater, FL); Extra Strength Antacid Tablets (Equate; Allegan, MI); Finest Natural Pharmaceutical Grade Calcium, 500 mg with Vitamin D (Walgreens; Deerfield, IL); Natural Oyster Shell Calcium Plus Vitamin D (Sundown; Boca Raton, FL); Nephro-Calci (R & D Laboratories; Marina del Rey, CA); Pharmaceutical Grade Calcium 600 (Walgreens; Deerfield, IL); Regular Strength Chewable Antacid Tablets (Equate; Allegan, MI); Natural Calcium 600 (Spring Valley; Salt Lake City, UT); Tums EX (Tums; Pittsburgh, PA); and Tums Ultra (Tums; Pittsburgh, PA).

The following prescription calcium formulas also contained no measurable lead content: Renagel (Genzyme; Cambridge, MA) and PhosLo (PhosLo; Braintree, MA).