Are calcium supplements safe?
That’s a tough call for consumers, considering that several prestigious health organizations and government agencies can’t agree on the answer.
But even the combatants in a new controversy about lead content in calcium supplements agree that Americans should continue taking the supplements, which help prevent the crippling bone disease osteoporosis. Adequate calcium intake is also crucial for pregnant women to assist in fetal development.
The bottom line on whether calcium supplements contain unsafe levels of lead, however, is still unraveling. And, in general, this appears to be a situation in which several organizations--all acting on behalf of consumers--have instead left them scared or confused.
“The most important message for people, from a public health standpoint, is that they should not be afraid to take calcium supplements,” says Jay Murray, a board-certified toxicologist and president of Murray & Associates, a private consulting firm in San Jose. “What we are talking about with lead [in the current controversy] is a theoretical risk. We have good, reputable scientists on both sides of the issue with disagreements on what this acceptable risk is.”
The monthlong controversy seems to be moving slowly toward a resolution that, ultimately, will upgrade the purity of calcium products taken by millions of Americans daily.
On Thursday, state Atty. Gen. Dan Lungren filed a lawsuit against several manufacturers for marketing calcium supplements that exceed lead content under the state’s Proposition 65. Lungren’s action was preceded by a lawsuit filed earlier last week on the same grounds by a nonprofit watchdog group, the Natural Resources Defense Council.
That same day, however, California Superior Court Judge William Cahill denied the NRDC’s request to issue a temporary restraining order prohibiting the sale of the calcium supplements that fail to carry a warning label on the lead risk, as mandated under Proposition 65.
While the actions by state authorities seem incongruous, they actually support a point that the warring parties agree on: The lead content in most calcium supplements sold today is probably not harmful. Nevertheless, many supplements clearly exceed the state’s strict Proposition 65, which was designed with a huge margin of error to protect consumers from environmental toxins.
Lead exposure raises anxieties in Americans because they have heard so much about the threat to children. Childhood lead poisoning has been linked to brain damage and developmental delays. The chemical is known to cause cancer and harm to the developing fetus.
Lead, however, is everywhere. It’s found in the air, water, soil and many foods.
“The public is so worried about contamination,” says Dr. David Heber, chief of clinical nutrition at UCLA. “But the amount of lead found in calcium supplements is the same as found in milk. It’s not something you can totally avoid. The most important thing is not to discourage consumers from taking calcium. [Calcium deficiency] is such a big public health problem.”
Most adults need at least 800 milligrams of calcium a day; pregnant and lactating women require at least 1,200 milligrams. But studies show that most adults get only 600 to 700 milligrams of calcium through diet. Thus, supplements have become popular and inexpensive aids.
The Food and Drug Administration and most manufacturers follow federal standards for acceptable trace lead levels. Calcium supplements that meet the federal standards are allowed to carry the USP (U.S. Pharmacopeia) label.
But the difference between Proposition 65 and the federal limit for trace lead content is huge: 0.5 micrograms under Proposition 65 compared to 7.5 micrograms under federal limits.
Proposition 65 “is lower than any other lead standard,” says Murray, who served as an advisor on a government panel evaluating Proposition 65 guidelines. “Proposition 65 requires a thousandfold uncertainty factor. It is designed to be a trigger for warning.”
Nevertheless, tests conducted recently at UC Santa Cruz on lead content in calcium supplements using Proposition 65 as a benchmark are disturbing. The products showing trace lead levels clearly exceeding Proposition 65 levels included Source Naturals Calcium Night (40 times the Proposition 65 standard), GNC Food Source Certified Calcium From Oyster Shell (10 times) and Os-Cal 500 High Potency Chewable Supplement (roughly six times).
While all those brands meet federal standards, the study and ensuing publicity has launched an advertising war, with Tums--which meets Proposition 65 standards--now billing itself as “the purest form of calcium available.
That’s not such a bad thing, says Dr. Gina Solomon, an NRDC scientist.
“We’re looking at the fact that people get lead from multiple sources in their daily lives. Some of these sources in food are unavoidable. But you can get lead out of [supplements]. And in cases where lead is avoidable, we want to make a change and decrease the total daily exposure,” she says. (Although lead and calcium are often found together in nature, some very pure sources of calcium carbonate are available in the United States, Solomon notes, as are manufacturing processes that can remove lead from calcium.)
But that doesn’t mean that calcium supplements exceeding Proposition 65 are unsafe, others argue.
“Obviously, the less lead, the better,” Murray says. “But different scientists will debate where the safe level for lead is.”
Moreover, all of the lead in a supplement does not necessarily reach the bloodstream, where it can do harm.
“One would have to know what blood levels arise as a result of ingesting more than 0.5 micrograms per day of lead before conclusions can be drawn about reproductive risk,” says Dr. Anthony R. Scialli, director of reproductive toxicology at Columbia Hospital for Women Medical Center in Washington, D.C.
A study published last year showed that calcium may, in fact, partially block the absorption of lead in the body. People who consume a lot of calcium may actually reduce their risk of lead exposure.
“The study found there was a slight decrease in blood-lead associated with calcium supplements,” Murray says. “That would make some sense because we know calcium inhibits the absorption of lead. That has been known for many years.”
Doctors have even prescribed a diet high in calcium to children who have suffered excessive lead exposure in hopes of blocking its absorption, he says.
Given the scientific complexities, the NRDC’s desire to have a dozen calcium supplements swept off the shelves was extreme, says Diane Shnitzler, a spokeswoman for the National Osteoporosis Foundation, which has been critical of the NRDC’s lawsuit.
The foundation also “fears that NRDC’s actions may cause irreparable harm to the public health by causing Americans to stop taking calcium supplements.”
Further efforts are needed to clarify how trace lead content affects blood levels of lead, Murray says. There are too few such studies on this now.
“On the other hand,” he says, “there are many studies showing the risk associated with not getting enough calcium.”