Calcium supplements have become very popular and are generally thought to be an effective way to promote healthy bone density. Indeed, calcium does have benefits but it's important to understand there are various forms of calcium and they all behave a little differently. Some supplements are worthwhile and some are merely the work of scoundrels trying to capitalize on false pretenses. Before you invest in a calcium supplement it's wise to understand a few things about calcium.
What is Coral Calcium?
Calcium is available in many forms- calcium carbonate, calcium citrate, calcium orotate, and that just names a few. Coral calcium, a form of calcium carbonate, is exactly what the name implies. It is calcium sourced from fossilized coral sources and is the most common form of calcium on the planet. A small, invertebrate animal polyp secretes a limey substance that hardens into the coral structure. This substance is calcium carbonate. If that description creates questions in your head about the sustainability of coral calcium harvesting, you're on the right track. Concerns have been raised as to the environmental harm from ravaging irreplaceable coral beds. Is it even worth it?
Is Coral Calcium Effective?
Calcium in the most simple form is rock, which the human body can't process. To deal with this, the body has a natural method called "chelating" which simply means that the calcium is combined or "coated with" another material. This other material, which may be an amino acid, is a substance the body can use and process. Chelating calcium with such a substance is done in attempt to make the body use and process the calcium as well.
Calcium citrate, for example, is simple calcium carbonate "chelated" with citric acid. The citric acid is considered food by the body, so calcium citrate is more easily absorbed into the body than calcium carbonate.
The stomach can also chelate calcium, and does, but, the older we get the less the body can chelate minerals and make them useful. Some forms of calcium, such as calcium orotate, incorporate advanced absorption mechanisms into their structure and may be beneficial for such situations.
False Claims of Coral Calcium
How effective is coral calcium? Well, it's hard to say. But, in January 2004, the Federal Trade Commission came down upon some calcium carbonate manufacturers for making improper claims about the abilities of calcium carbonate and making claims that a coral calcium dietary supplement was able to cure cancer, multiple sclerosis, heart disease, high blood pressure, and other serious diseases. The defendants were also reprimanded for claiming that the body absorbs coral calcium better than other calcium supplements. 
This is exactly why it's imperative for you to investigate nutritional supplements on purpose and through research, not commercials! To market coral calcium with the promise of it being able to cure cancer isn't just incorrect and ludicrous it's immoral. Shame on them.
Coral Calcium Research
Coral calcium hasn't provided many mind-blowing advances for the research community. The Department of Orthopaedic Surgery at Mahidol University in Bangkok collected samples of calcium carbonate salts and analyzed them for lead, cadmium and mercury. Every sample of the calcium carbonate contained lead.  A Japanese study with only 12 volunteers examined the effects of ingesting coral calcium via a cracker. Researchers did note a few interesting notes about observed absorbability but largely concluded that the data set was inconclusively small. 
Surprisingly, coral calcium has been shown to be useful in at least one application. A German surgeon had reported successfully using natural coral calcium for maxillofacial surgery bone grafting applications. 
Stick With What Works
For effective calcium supplementation, I only recommend calcium orotate. Calcium orotate is the single most effective form of calcium available. The orotate transfer system allows for calcium to penetrate into the cells that need it most. That is why we formulated IntraCal™. This calcium supplement combines calcium orotate and magnesium orotate, two vital nutrients that support healthy teeth and bones, the nervous system, and cardiovascular health. It is the only calcium supplement I use and is the most bioavailable calcium supplement available.
- Federal Trade Comission. Marketers of coral calcium product are prohibited from making disease treatment and cure claims in advertising. 2004 January 22.
- Bunyaratavej N, Buranasinsup S. Calcium supplement: humanity's double-edged sword. J Med Assoc Thai. 2011 Oct;94 Suppl 5:S56-8.
- Ishitani K, Itakura E, Goto S, Esashi T. Calcium absorption from the ingestion of coral-derived calcium by humans. J Nutr Sci Vitaminol (Tokyo). 1999 Oct;45(5):509-17.
- Soost F, Reisshauer B, Herrmann A, Neumann HJ. [Natural coral calcium carbonate as alternative substitute in bone defects of the skull]. Mund Kiefer Gesichtschir. 1998 Mar;2(2):96-100. German.
†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.