Consumer concerns on calcium supplements: bioavailability, source sustainability, cost and marketplace positioning impact calcium supplementation choices

Prepared Foods, Sept, 2003 by Kerry Hughes

Many forms of calcium supplements are now on the market and all advertise attractive benefits. With the high rates of osteoporosis in the U.S., the fact that many Americans do not get enough calcium, the recent review published by ConsumerLab.com and the sales of calcium supplements in the U.S. in 2001 being some $775 million (according to the Nutrition Business Journal), the controversy as to which form of calcium provides the most benefit seems never more important.

However, the closer calcium supplementation is examined, the more questions arise. To ascertain the best regimen for calcium supplementation, important factors are not only cost and the bioavailability of individual calcium forms, but also associated nutrients, how well the supplement is tolerated and retained in the tissues, as well as what other lifestyle factors might contribute to a calcium supplement regimen.

Recent Review Fuels Calcium Controversy

Consumerlab.com (White Plains, N.Y.) released a review of calcium supplements in June this year--with the bad news that 20% of calcium supplements tested had problems. Of the 25 calcium supplements analyzed, two contained lead in excess of California's "no significant risk level." Additionally, one of these products failed to break apart during disintegration testing, and a third product contained only 77% of the labeled amount of calcium.

Other issues haunt popular calcium supplements present and past. For example, unrefined calcium sources such as oyster shell, bone meal, and dolomite were once popular but have fallen out of favor due to high levels of toxic metals (such as lead). Here's a look at other products currently in the spotlight.

* Coral Calcium. Coral calcium is the current leader of the calcium supplement controversy. Manufacturers of these products assert that their calcium is one of the most bioavailable, supported by the claim that Okinawan's native population (where coral calcium is produced) has a very low incidence of disease and high longevity. There is some research that shows coral-derived calcium is better absorbed than "pure" calcium carbonate, perhaps due--in part--to factors such as coral calcium's magnesium content. Depending on the brand, coral calcium generally contains some 20-40% calcium and 0.5-20% magnesium. Since the calcium to magnesium ratio varies between brands (and source), some companies are adding magnesium to increase its ratio.

Another issue involves the sustainability of the source of coral calcium. Many are aware of the serious environmental deterioration of coral reefs, and there is concern that gathering coral calcium contributes to this problem. Manufacturers claim to be mining in eco-friendly ways, taking the coral only from the beach or the ocean floor so as not to disturb the living coral reefs. However, some argue that harvesting the dead coral lying on the ocean floor disturbs the sediment, which harms living coral.

Tod Cooperman, M.D., president of ConsumerLab.com, said in a recent press release, "We have received many questions from consumers about coral calcium. Coral calcium is not inherently better or worse than other types of calcium. But it is sadly ironic that the most advertised brand also had the most lead."

The Council for Responsible Nutrition (Washington) also has asked the Food and Drug Administration (FDA) to crack down on the "miracle cure"-type claims that these manufacturers are making on the coral calcium products.

* Calcium Carbonate. Calcium carbonate is the least expensive and most common calcium form on the market and is found, for example, in antacid tablets such as Turns. An estimated 85% of all calcium supplements contain calcium carbonate. Calcium carbonate is also the most concentrated form of calcium (Ca++) on the market, giving two times the elemental calcium by weight as the citrate form, allowing for smaller quantities of use.

Calcium carbonate in antacids requires stomach acid to dissolve and has a potent "neutralizing" or buffering effect. Long-term use of calcium carbonate antacids, however, may result in side effects and is associated with gastric reflux, gas, constipation and bloating. Calcium carbonate is not absorbed as well as the citrate form, especially in people with low gastric acid levels, such as the elderly. Calcium carbonate and citrate both partially inhibit the absorption of iron when taken with food. (1)

* Calcium Citrate. The second most inexpensive and common form of calcium on the market is calcium citrate. Calcium citrate has been shown in a meta-analysis to be better absorbed than calcium carbonate by approximately 22-27% either with meals or on an empty stomach. (2) Calcium citrate does not need as low a pH to dissolve as calcium carbonate. Calcium citrate, but not carbonate, enhances the absorption and deposition of aluminum from food sources into human tissues (Nolan, 1994).

* Calcium Chelates. Amino acid chelates, generally, are superior forms of minerals for absorbability, but have cost considerations. Additionally, some supplement suppliers carry what they claim to be amino acid chelates, when they are not. The National Nutritional Food Association--NNFA (Newport Beach, Calif.) defines a chelate very specifically, and several criteria must be met in order for chelation to actually occur. Of the claimed "chelates" on the market are the various Krebs (Citric Acid) Cycle chelates, such as citrate, malate, and aspartate. Dicalcium malate is a newer form of a true calcium chelate. It contains a high amount of calcium (30%).