What Is Coral Calcium?

Purported benefits lack evidence, prompting FTC action against some sellers

Coral calcium tablets, capsules, and powder

Verywell / Anastasia Tretiak

Coral calcium is a form of calcium derived from coral reefs. Much of the hype around using coral calcium for health purposes stems from the fact that the ingredient is harvested in Okinawa, Japan, an area well-known for residents with the longest life expectancy in the world.

Some have tied the health of Okinawans to coral calcium intake (via their water supply), but research does not back this up. Several large health organizations have published reports to this end.

In addition, the Federal Trade Commission (FTC) took legal action in 2004, and won a subsequent appeal in 2010, against companies who sell coral calcium supplements for making false and unsubstantiated claims that coral calcium could treat or cure serious diseases.

What Is Coral Calcium Used For?

The term coral calcium was made popular in the early 2000s by Robert R. Barefoot who began to sell books, supplements, and other products promoting the purported benefits of this type of calcium and linking it to the health of Okinawans.

People have used coral supplements to treat conditions including multiple sclerosis, cancer, heart disease, and other chronic health problems.

Studies, including the well-known Okinawa Centenarian Study, have shown that Okinawans not only live the longest but have low rates of heart disease and cancer. But there is no evidence that this is tied to coral calcium consumption, as Barefoot and other marketers have claimed.

In fact, researchers involved with the Okinawa Centenarian Study have outright debunked the claim. They issued a position paper in 2003 stating that the longevity of the Okinawans is instead due to their healthy lifestyle.


Independent, high-quality studies supporting coral calcium as a dietary supplement or as a health treatment are limited and provided little evidence to support its use as a treatment for any illness or to provide health benefits.

Furthermore, in the appeal regarding legal action taken by the FTC, the courts upheld a $48.5 million settlement against coral calcium product companies saying that there was a "complete absence of support for the vast majority of health claims" associated with the "bogus" supplements.

Several large health organizations—including the Multiple Sclerosis Foundation and the Academy of Nutrition and Dietetics— have published reports advising against believing claims associated with coral calcium supplements. Some even warn consumers that taking coral calcium may have adverse side effects.

Coral Calcium vs. Other Types of Calcium

Coral calcium is calcium carbonate, the most common type of calcium on the market. Coral calcium isn't believed to be chemically different from other calcium carbonate products, as the aforementioned reports clearly state.

Indeed, health experts have reported that coral calcium contains the same ingredients as calcium carbonate products, such as Tums, commonly found in grocery stores and pharmacies.

Although coral calcium supplements may contain small amounts of trace elements, such as manganese, there is no evidence supporting the potential benefits of these minerals in trace amounts.

Dietary calcium—and potentially calcium supplements—may play a role in the treatment of certain conditions including bone loss, osteoporosis, colon cancer, heart disease, and hypertension. But investigators are still evaluating the extent of the benefits and whether or not supplements can be as effective as calcium consumed in food.

Possible Side Effects

Coral is sometimes used by surgeons to replace bone. It is likely safe when used for this purpose. However, there is not enough evidence to determine if coral calcium supplements are safe when consumed by mouth. Furthermore, some coral calcium supplements may contain lead.

People with shellfish allergies may develop allergic reactions after ingesting coral calcium supplements.

Women who are pregnant or breastfeeding are advised to avoid coral calcium supplements.

Dosing and Preparation

Coral calcium supplements are found in tablet and softgel forms. There is no typical dose for coral calcium.

It's important that you consult with your healthcare provider before starting coral calcium for a few reasons:

  • The dosage per tablet/capsule and recommended daily intake varies by manufacturer.
  • Your calcium needs and the safest dose for you depends on several factors, including your health status and age.
  • The amount of coral calcium you consume, and when, can affect its absorption as well as that of other nutrients. This may be a particular concern if you have issues such as iron deficiency.

Never exceed the recommended dose on the product label. Excessive intake of calcium can result in hypercalcemia (elevated calcium in the blood.

What to Look For

Dietary supplements are largely unregulated by the Food and Drug Administration (FDA). Although it is illegal to market a dietary supplement as a treatment or cure for a specific disease or to alleviate the symptoms of a disease, the agency does not test supplement products for safety or effectiveness.

In some cases, dietary supplements may deliver doses that differ from the amount indicated on the label. When choosing a supplement, it's best to look for products that have been certified by ConsumerLabs, U.S. Pharmacopeia, or NSF International. These organizations don't guarantee that a product is safe or effective, but they do provide a certain level of testing for quality. 

Other Questions

How does coral calcium form?
Live coral is composed of marine organisms (polyps) that live in colonies. It forms a hard shell to protect itself, but also to help it grow. These coral skeletons are composed of aragonite, a form of calcium carbonite that is created as the result of a chemical reaction inside these polyps.

How much calcium is in coral calcium?
Almost a quarter of coral calcium is pure calcium. Magnesium and dozens of other minerals make up the rest of its composition.

Are products labeled "sea calcium" coral calcium?
Most products labeled "sea calcium" are made from algae. However, this is not a regulated term, so be sure to check labels to see exactly what products you are considering contain. Other sources of marine calcium besides coral and algae include shells and fishbones.

Is coral calcium affected by environmental changes?
Yes. The process by which coral generates coral calcium is a delicate one. According to research published in the Proceedings of the National Academy of Sciences of the United States of America in 2018, ocean acidification (which is largely due to the burning of fossil fuels) reduces carbonate ions that coral uses to construct their skeletons.

A Word From Verywell

Due to the limited research, it's too soon to recommend coral calcium for any health purpose. It's also important to note that self-treating a condition and avoiding or delaying standard care may have serious consequences. If you're considering using coral calcium, make sure to consult your healthcare provider first.

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11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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