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Coral Calcium

Chemically it is calcium carbonate with trace minerals, sold on infomercial claims about curing hundreds of diseases that produced US regulatory enforcement rather than clinical trials. There is no human study showing it outperforms ordinary calcium carbonate, and natural-source calcium supplements have a documented lead contamination problem.

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What the science says

  • It is calcium carbonate with a story attached Limited evidence

    Coral calcium is harvested or fossilised coral, over 90% calcium carbonate plus trace magnesium and other minerals. No published human trial demonstrates superior absorption, bone effects, or any clinical outcome versus a plain calcium carbonate tablet costing a fraction as much.

  • The famous health claims were an enforcement matter, not a research finding Limited evidence

    The "Okinawan longevity" and cure-for-200-diseases marketing of the early 2000s drew US Federal Trade Commission and FDA action against the promoters for deceptive and unsubstantiated claims, including claims that coral calcium treats cancer. Contemporary clinical commentary reviewing the claims found no evidence supporting extensive health benefits beyond those of calcium itself.

  • Natural-source calcium carries a real contamination risk Moderate evidence

    An analysis of 70 brands of calcium supplements found lead levels from 0.03 to 8.83 µg/g, with about 25% of products exceeding the FDA provisional total tolerable daily lead intake for children under 6, and natural-source products among the worst offenders. A 2022 analysis of mineral and multimineral products confirmed lead remains detectable across the category. Unrefined marine-source calcium is exactly the type of product where this matters.

Dosage & safety

Studied doseLabels typically list 1,000-1,500 mg coral calcium, delivering roughly 200-400 mg elemental calcium — well short of a full daily dose, so read the elemental figure. No dose has ever been studied for any coral-calcium-specific claim. If you need calcium, the studied doses are 500-600 mg elemental per serving to a total intake of 1,000-1,200 mg/day.
SafetyHeavy metal contamination — lead in particular — is the principal concern; choose only third-party tested products, or avoid the category. All standard calcium risks apply: constipation, hypercalcaemia at excessive intakes, and blocked absorption of levothyroxine, iron, tetracyclines, quinolones and bisphosphonates (separate by 2-4 hours). Do not exceed 2,000-2,500 mg/day total calcium. Regulatory note: US marketers of coral calcium have been subject to FTC judgments for deceptive disease claims, and harvesting living coral is restricted or prohibited in many jurisdictions on conservation grounds.

How to take it

TimingTiming does not matter; split amounts above 600 mg elemental.
With food?With food.
Worth knowingThere is no calcium-specific advantage to the coral source — an ordinary citrate or carbonate delivers more elemental calcium for less money and without the lead question.

Interactions

With medications

  • levothyroxine

    calcium reduces levothyroxine absorption separate by at least 4 hours

  • tetracycline and quinolone antibiotics

    chelation cuts antibiotic absorption separate by 2–4 hours

  • bisphosphonates

    blocked absorption separate by at least 2 hours

  • thiazide diuretics

    reduced calcium excretion raises hypercalcaemia risk have serum calcium checked if you take both

With other supplements

  • iron supplements

    calcium competes with iron for absorption take them at different times of day

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Is coral calcium better than regular calcium?

No. Coral calcium is over 90% calcium carbonate, and no human trial shows it outperforms a plain calcium carbonate tablet costing a fraction as much.

Does coral calcium cure diseases?

No. The claims that coral calcium cures cancer and hundreds of diseases led US FTC and FDA action against the promoters for deceptive and unsubstantiated claims, not to clinical trials.

Does coral calcium contain lead?

Natural-source calcium supplements, including coral calcium, have a documented lead contamination problem, with about 25% of products in one analysis of 70 brands exceeding a tolerable lead limit for young children. If you take coral calcium, choose only third-party tested products.

Scientific references

Where to buy

NOW Foods, Coral Calcium, 1,000 mg, 250 Capsules

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