Health Care Professional Information

Scientific Name
Goniopora species; Porites species
Brand Name

Okinawa coral calcium

Clinical Summary

Coral calcium is derived from the natural matrix of coral. Coral particles that drift to the sea bottom from natural erosion are harvested from a wide region of tropical oceans. This substance is promoted as a “natural calcium supplement.” Limited studies suggest that calcium of coral origin is better absorbed in the intestine than calcium from other sources, thought due to the natural 2:1 calcium: magnesium ratio that occurs in coral (1) (3). Claims of coral calcium's ability to maintain a proper pH balance in the human body are unsubstantiated.

There is no evidence of anticancer properties of coral calcium.
Coral calcium supplements cost many times that of other calcium supplements that have similar physiological effects. In addition, direct harvesting of natural coral reefs contributes to the destruction of coral reef ecosystems and the wide diversity of marine life that depend on this habitat. Oral coral calcium supplements should not be confused with the coral matrix used in surgery and bone grafting.

For more information on calcium supplementation, please read our monograph on calcium .

Purported Uses
  • Arthritis
  • Cancer prevention
  • Diabetes
  • Fatigue
  • Osteoporosis
Constituents

Calcium, magnesium

Mechanism of Action

Corals contain 20% calcium and 10% magnesium by weight. This ratio compares favorably to the recommended daily allowances of these two minerals (3). Studies suggest that concomitant magnesium intake has an additive effect on calcium absorption. Therefore, greater calcium absorption and bioavailability may result from coral calcium supplementation, but no other benefits have been shown over other calcium supplements (1).

Warnings

The FTC and FDA have issued warnings to numerous Web site operators who promote coral calcium (6).
An independant testing company found that some calcium supplements contain excessive amounts of lead (5).

Contraindications

Patients with high serum calcium level or low serum phosphate level should consult their physicians before taking calcium supplements.

Adverse Reactions

Coral does not appear to have adverse effects beyond those associated with other forms of calcium supplementation (3). Other natural calcium supplements have shown lead contamination (4).

Literature Summary and Critique

Ishitani K, et al. Calcium absorption from the ingestion of coral-derived calcium by humans. J Nutr Sci Vitaminol (Tokyo) 1999;45:509-17.
Twelve adult volunteers were tested in a crossover study that was neither randomized nor blinded. Calcium levels were measured after ingesting 525 mg of calcium either from coral source or calcium carbonate source. A control group is mentioned, although no data are given for the group. While this study suggests better absorption of a coral calcium supplementation over calcium carbonate, larger better designed studies need to be undertaken to confirm this observation. Furthermore, a study to compare coral calcium to a supplement plan with the same calcium to magnesium ratio would better explain whether coral itself has inherent benefit over other forms of supplementation.

References
  1. DerMarderosian A, editor. The Review of Natural Products. St. Louis: Facts and Comparisons; 1999.
  2. Vuola J, et al. Compressive strength of calcium carbonate and hydroxyapatite implants after bone-marrow-induced osteogenesis. Biomaterials 1998;19:223-7.
  3. Ishitani K, et al. Calcium absorption from the ingestion of coral-derived calcium by humans. J Nutr Sci Vitaminol (Tokyo) 1999;45:509-17.
  4. Ross EA, Szabo NJ, Tebbett IR. Lead content of calcium supplements. JAMA 2000;284:1425-9.
  5. ConsumerLab.com, LLC. http://www.consumerlab.com/. Accessed May 5, 2011.
  6. Federal Trade Commission. FTC Charges Marketers of Coral Calcium Supreme Dietary Supplement and a Pain-Relief Product With Making False and Unsubstantiated Claims http://www.ftc.gov/opa/2003/06/trudeau.shtm. Accessed May 5, 2011.

Consumer Information

How It Works

Bottom Line: Coral calcium has not been shown to treat or prevent cancer.
Coral calcium supplements contain calcium and magnesium. Studies have suggested that ingestion of magnesium at the same time as calcium allows greater calcium absorption by the intestine. It has been claimed that coral calcium can maintain a proper pH balance in the human body, but there is no evidence to support these claims. Furthermore, there is no scientific evidence for the anticancer properties of coral calcium.

Please see calcium and magnesium monographs for more information on the biological effects of these minerals.

Purported Uses
  • To treat arthritis
    No laboratory or clinical studies have evaluated coral calcium for arthritis.
  • To prevent cancer
    This claim is not backed by research.
  • To treat diabetes
    No scientific evidence supports this use.
  • To alleviate fatigue
    This use is not supported by any evidence.
  • To prevent and treat osteoporosis
    No laboratory or clinical studies have tested coral calcium for osteoporosis.
Research Evidence

The only clinical trial to test the use of coral calcium is a small, poorly designed study. Twelve healthy adult volunteers were asked to eat crackers containing either calcium carbonate (i.e., a typical calcium supplement) or coral calcium, and their blood and urine levels of calcium were measured. Later in the study, the volunteers were asked to eat the other set of crackers, and measurements were repeated. Although the crackers with coral calcium allowed a greater amount of calcium to be absorbed into the blood stream, it was not assessed whether this is a clinically relevant finding, or whether any beneficial biological effects will occur from coral calcium compared to calcium carbonate. In addition, the researchers in this study were not “blinded” as to which patients were receiving the coral calcium, which can lead to bias in the study results.

Patient Warnings
  • Coral calcium supplements may cost many times more than other calcium supplements that have similar effects on the body. In addition, the harvesting of coral contributes to the destruction of already-threatened coral reef ecosystems and the wide diversity of marine life that depend on this habitat.
  • The FTC and FDA have issued warnings to numerous Web site operators who tout unsubstantiated benefits for coral calcium.
  • A recent test of a number of coral calcium supplements by an independant lab found one that contained excessive amounts of lead.
Do Not Take If
  • You have high blood levels of calcium or low blood levels of phosphate. Such patients should consult their doctor before taking calcium supplements.
Side Effects
  • Constipation
  • Flatulence
  • Chalky taste
  • Dry mouth
  • Nausea
Special Point

Oral coral calcium supplements should not be confused with the coral matrix used in surgery and bone grafting.

E-mail your questions and comments to aboutherbs@mskcc.org.