Pulse of Oriental Medicine: Alternative Medicine That Works for Regular Folks
Coral Calcium


Coral Calcium Supplements...
Don't Believe The Hype
by Brian Carter, MS, LAc

Brian is the founder of the Pulse of Oriental Medicine. He teaches at the Pacific College of Oriental Medicine and maintains a private acupuncture and herbal practice in San Diego, California, and is the author of Powerful Body, Peaceful Mind: How to Heal Yourself with Foods, Herbs, and Acupressure.
I have a question about coral calcium. Are there any prescription drugs you shouldn't take with coral calcium. Can you take it if you are allergic to shellfish?

There is so much hype about coral calcium... because it's being marketed and sold directly to consumers. It's pretty safe because it's just Calcium (Ca) Carbonate, but all that marketing carries with it the danger of deception.

Time Magazine's March 14th article on this topic was titled, "Coral Calcium: A Barefoot Scam."

Coral Calcium is Calcium Carbonate plus Magnesium

Coral calcium is no great medical breakthrough- it's basically TUMS without the sugar! Calcium carbonate is great for acid reflux, because it absorbs acid. It also can get calcium into your bloodstream, but not as well as Calcium Citrate does.

As one pundit put it, the value of Calcium for human beings is not the question. It is the value of this form of calcium, and that validity of the marketers' claims that we must examine.

Calcium Absorption: Calcium Carbonate vs. Calcium Citrate

A 1999 meta-analysis of 15 studies including 184 people found that absorption of Calcium Citrate was 20% higher than that of Calcium Carbonate. That means 20% more of the citrate gets into your bloodstream than the carbonate.

A 1999 Japanese study did find that coral calcium was absorbed better than the average calcium carbonate.

Coral Calcium Interacting with Drugs?

As to it affecting prescription drugs, the first thing you need to know is that Ca Carbonate is an antacid, so it can prevent the absorption of any herbs or pharmaceutical drugs that you take.

Coral Calcium is an Antacid

Antacids reduce your ability to absorb many drugs. If you are taking an important drug, you may not absorb enough of it for it to have its intended effect. You may want to talk to your doctor about the dosage of your drugs; ask them if they think the dosage needs to be increased since you are taking Ca Carbonate.

This can be quite serious if you are on a drug with a narrow therapeutic margin like coumadin/warfarin, or another drug that prevents life-threatening consequences (e.g. blood pressure medications that prevent heart problems and stroke, or phenytoin which prevents seizures and is directly affected by antacids- see below).

Specific Drug Interactions of Calcium Carbonate

The effects of these are decreased by antacids:

  • Iron
  • Itraconazole (Sporanox)
  • Ketoconazole (Nizoral)
  • Phenytoin (Dilantin)
  • Quinolones
  • Rofecoxib (Vioxx)
  • Tetracyclines

The effects of these are increased by antacids:

  • Quinidine

Antacids also affect folic acid, copper, phosphate, and potassium.

Coral Calcium and Shellfish Allergy

As for the shellfish question, it is indeed a risk.

Every resource I could find said to consult your physician, which I interpret as an attempt to shift the responsibility onto your doctor.

Allergist Morris Nejat, M.D. says, "Shellfish, or crustaceans are generally cross reactive. If you're is allergic to one, you should avoid all of them."

So I'd say play it safe, and avoid it.

You can take Calcium Citrate instead, which absorbs better anyway.

In fact, you might take Citrate instead just on general principle - So that you aren't encouraging health-supplement scam-artists.

All the best,


  1. Lacy, Armstrong, Goldman, Lance. Drug Information Handbook.
  2. Caregroup.org - Antacids
  3. Chen, J. Herb-Drug Interactions: What Every Patient Needs to Know
  4. Miami Herald - "Little evidence to support grandiose claims for coral calcium"
  5. Nejat, M. Individual Allergies.
  6. Sakhaee K, Bhuket T, Adams-Huet B, Rao DS. Meta-analysis of calcium bioavailability: a comparison of calcium citrate with calcium carbonate. Am J Ther 1999 Nov;6(6):313-21
  7. 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.

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