Coral calcium is a supplement usually derived from coral sand deposits. These sand deposits, which were once part of a coral reef, are typically collected directly from coastal land or shallow waters surrounding it.

To manufacture coral calcium, the coral sand deposits are first refined to remove any pollutants or other unwanted substances, then ground into a powder. This powder is sold as-is or packaged into capsules.

Coral calcium supplements are comprised largely of calcium carbonate but may also contain small amounts of magnesium and other trace minerals (1).

Coral calcium’s composition is similar to that of human bone and has been used as bone graft material for over 30 years (1).

Nowadays, it’s mostly used to prevent or treat low calcium levels among those who don’t get enough of this nutrient through diet alone. Although it’s said to offer many additional health benefits, most of these aren’t currently supported by science.

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Proponents assert that coral calcium boasts a range of health benefits, from stronger bones and fewer arthritis symptoms to protection from cancer and Parkinson’s disease.

However, very few of these claims are backed by evidence.

May improve bone health

Calcium plays important roles in your body and is critical for muscle contraction, as well as keeping your bones strong and healthy.

A diet containing too little calcium may cause this mineral to leach from your bones, weakening them over time. Conversely, calcium-rich diets have been consistently linked to stronger, healthier bones.

This link appears especially strong when you consume calcium from food, but supplements may aid people who are unable to get enough calcium from their diet (2).

Unlike other calcium supplements, coral calcium naturally contains magnesium and small amounts of trace minerals. Some experts suggest that this combination may be more beneficial to bone health than calcium alone (1).

One small, older human study further suggests that coral calcium is easier to absorb than the type found in most calcium supplements (3).

Moreover, an animal study reports that mice given coral calcium had slightly more bone mineral content (BMC) and bone mineral density (BMD) in the femur than those given regular calcium supplements (1).

Nonetheless, there’s limited support for these results overall.

May reduce blood pressure

Several studies link high calcium intake to slightly lower systolic blood pressure, which is the upper number on a blood pressure measurement.

That said, this benefit seems to only apply to people who already have high blood pressure (4).

Similarly, some research suggests that high calcium intake during pregnancy may reduce the risk of preeclampsia — one of the leading causes of maternal and infant illness and mortality (2, 5).

Preeclampsia is a serious complication marked by high blood pressure levels during pregnancy. It usually develops after 20 weeks of gestation and affects up to 14% of pregnancies worldwide (6).

Furthermore, rat studies suggest that coral sand’s natural magnesium and silica content may contribute to its blood pressure effects (7).

Yet, additional research is needed before strong conclusions can be made.

Other potential benefits

Coral calcium may also offer a few additional benefits:

  • May prevent cavities. Test-tube research suggests that coral calcium may protect against dental cavities by remineralizing the enamel of your teeth (8).
  • May support brain health. Mouse studies note that coral calcium may help slow age-related loss of brain function (9, 10).

All the same, further research is necessary.

Coral calcium is generally considered safe. Still, you should keep a few downsides in mind.


Coral reefs may be contaminated with heavy metals like mercury or lead. As such, it’s best to avoid coral calcium sourced from highly polluted waters (11).

Moreover, you may want to research which measures a manufacturer has taken, if any, to ensure that contaminant levels in its supplements remain low.

Risks of excessive intake

Ingesting high amounts of coral calcium may cause hypercalcemia, which is characterized by excessively high levels of calcium in the blood. This condition may result in health problems, particularly in your heart and kidneys (2, 12).

High calcium intake may also be tied to an increased risk of heart disease and prostate cancer. However, more research is needed (2, 12, 13).

Digestion and absorption

Coral calcium supplements may also cause digestive problems, such as gas, bloating, and constipation (2).

In addition, taking coral calcium with food may lower your body’s ability to absorb nutrients like iron and zinc (2).


Serious allergic reactions to coral calcium appear to be uncommon.

However, seek immediate medical attention if you experience a rash, hives, severe dizziness, trouble breathing, or swelling of the mouth, lips, tongue, throat, or face after consuming coral calcium.

Due to limited research, there’s no recommended dosage for coral calcium.

Based on information available from other forms of calcium supplements, dosages may range from 600–2,000 mg per day (2).

You can take this supplement with or without food. Taking it with food may reduce the likelihood of an upset stomach but lower your body’s ability to absorb nutrients like iron and zinc (2).

Taking coral calcium with vitamin D may boost calcium absorption.

Research is mixed on whether taking smaller, more frequent doses of calcium alone — rather than alongside other minerals — maximizes absorption (2).

Overdosing on coral calcium may result in excessively high blood calcium levels, or hypercalcemia, which may cause heart and kidney problems (2).

The safe daily upper intake level (UL) for calcium is 2,500 mg per day for adults under the age of 50 and 2,000 mg per day for those 50 or older. The UL increases to 2,500–3,000 mg per day if you’re pregnant or breastfeeding, depending on your age (2).

These ULs are based on a combined calcium intake from foods and supplements. That said, excess calcium intake from supplements are considered more problematic (2, 12).

Symptoms of hypercalcemia include poor appetite, frequent urination, unexplained weight loss, fatigue, and an irregular heartbeat (12).

If you suspect an overdose, call your local poison control center for guidance.

Calcium supplements, including coral calcium, may interact with various medications, such as antibiotics, diuretics, anti-seizure medicine, and medications to treat bone or Paget’s disease (2).

Depending on the medicine, you may need to wait a certain amount of time after medicating before you supplement with coral calcium.

Those currently taking any type of medication should consult their healthcare provider for advice before starting to take coral calcium supplements.

Very little research is available regarding the best way to store and handle coral calcium.

Still, manufacturers typically recommend that it be kept at room temperature, in a dry location, and away from direct sunlight.

No studies have examined the safety of coral calcium during pregnancy or breastfeeding.

Kidney stone risk is normally elevated during pregnancy, and excess calcium intake may further increase this risk. Similarly, excess calcium intake while breastfeeding is associated with heart and kidney problems and may increase your risk of hypercalcemia (12).

If you’re pregnant or breastfeeding, no evidence currently suggests that you benefit from calcium supplements — including coral calcium — if you already get enough of this mineral from your diet.

Moreover, coral calcium supplements are sometimes contaminated with pollutants like mercury and lead, which may be passed on to your baby (11).

In such instances, coral calcium may provide more risks than benefits. If you don’t meet your daily requirements for this mineral from food alone, you may want to choose a different type of calcium supplement.

Due to limited research, strong recommendations on the safety of coral calcium supplements in specific populations don’t exist.

Although more studies are needed, a high calcium intake may be linked to an increased risk of heart disease and prostate cancer (2, 12, 13).

Hypercalcemia caused by excess calcium intake from supplements may also cause heart problems, kidney stones, and impaired kidney function. Thus, individuals with preexisting heart or kidney issues may wish to avoid all calcium supplements, including coral calcium (2, 12).

Coral calcium is sometimes said to safeguard against certain cancers, but research is mixed — with some studies even suggesting a higher cancer risk (13, 14, 15, 16, 17, 18).

Further research suggests that coral calcium may combat arthritis and Parkinson’s disease. Yet, these benefits appear to be linked to specific compounds in soft corals, which differ from the hard corals used to make coral calcium supplements. More studies are needed (19).

The two most common alternatives to coral calcium are calcium carbonate and calcium citrate.

Calcium carbonate supplements contain the same type of calcium found in coral calcium but typically lack the additional magnesium and trace minerals. They’re the cheapest and most readily available form but are best taken with food (2).

Calcium citrate is absorbed equally well when taken with or without food. It’s typically prescribed to people with low levels of stomach acid, inflammatory bowel disease (IBD), or other gut disorders (2).

Other forms of calcium used in supplements or foods include calcium gluconate, calcium lactate, and calcium phosphate.

Speak to your healthcare provider for advice on which form of calcium, if any, is best for you.