Calcium carbonate

Studies in people

• Open question

  How well calcium is absorbed³

  Scientists do not yet know whether calcium carbonate needs stomach acid to be absorbed well.

• Benefit

  Phosphate levels in dialysis patients⁵

  In dialysis patients, eating cheese made with added calcium carbonate lowered phosphate levels between treatments.

• Benefit

  Bone density in teenagers⁶

  In teens with HIV and low vitamin D, calcium carbonate plus vitamin D3 improved bone density.

• Concern

  Thyroid hormone absorption⁷

  Taking calcium carbonate within two hours of thyroid pills raised TSH and cholesterol in women.

• Open question

  Bone strength in children⁸

  In children with HIV, calcium carbonate with vitamin D3 is being tested to see if it helps bones grow stronger.

• Benefit

  Calcium absorption in teen girls⁹

  In teen girls, calcium carbonate supplements helped the body hold onto more calcium than a placebo, but smaller particles were no better.

• Open question

  Calcium absorption after stomach surgery¹⁰

  In people who had gastric bypass, calcium citrate was absorbed better than calcium carbonate.

• No harm found

  Calcium absorption from supplements¹¹

  In women, calcium carbonate raised blood calcium no more than a placebo pill did.

• No harm found

  Blood pressure¹²

  Calcium carbonate did not lower blood pressure in people with mild high blood pressure.

• Concern

  Iron absorption from food¹³

  In women, taking calcium carbonate with a meal cut how much iron their bodies absorbed from that food.

• Open question

  Bone strength in children with HIV¹⁴

  In children with HIV, calcium carbonate with vitamin D3 is being tested to see if it helps bones grow stronger.

• Benefit

  Bone breakdown after menopause¹⁶

  In postmenopausal women, calcium carbonate and milk both lowered bone breakdown, and visceral fat did not change this.

• Open question

  Child growth after pregnancy supplements¹⁹

  Calcium carbonate taken in pregnancy led to higher growth signals in boys but lower ones in girls years later.

• Benefit

  Calcium absorption after weight-loss surgery²⁰

  In people who had weight-loss surgery, calcium citrate raised calcium absorption more than calcium carbonate did.

• Benefit

  Bone breakdown in older women²¹

  In older women, calcium citrate lowered bone breakdown markers, while calcium carbonate did not change them.

Found in some samples or products

These come from where it was grown, how it was processed or cooked, or what it was made into. They are not about the ingredient itself, so the signal does not count them.

• Aluminium in infant formula²⁴

  Calcium carbonate used in infant formula can carry aluminium, which the experts said is a concern.

How it’s made and used

• How much calcium the body absorbs⁴

  In people, calcium from calcium carbonate was absorbed about as well as from another calcium supplement.

• Calcium absorption from soymilk¹⁵

  In women, the body absorbed calcium from calcium carbonate-fortified soymilk as well as from cow's milk.

• Kidney stone risk¹⁷

  In eight healthy men, calcium carbonate plus citrate had an added effect on one urine stone risk factor.

• Bone health after stomach surgery¹⁸

  In people who had gastric bypass, calcium carbonate and calcium citrate changed parathyroid hormone levels about the same.

• Blood calcium levels²²

  Calcium carbonate supplements raised calcium in the blood for hours after each dose, and this repeated with daily use.

• What it does in food²³

  Calcium carbonate is used in food to carry nutrients and hold mixtures and gels together.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.