My diet:

E170 Calcium carbonate

E170Acidity regulatorsOrigin: Mineral
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Every diet

VeganYes

Almost always mined limestone. Shell-based versions are rare and usually labeled as such.

Gluten-freeYes
HalalYes
KosherYes
KetoYes
Low-FODMAPYes
The short answer
Calcium carbonate (E170) is ground limestone, the same calcium found in antacids. It adds calcium to plant milks and flour and is very safe.
Generally safe

Fine for most people at normal amounts.

E-numberE170
Comes fromMineral
What it doesAcidity regulators
Glycemic index—
Daily limitNot set
Also calledCalcium carbonate, Ground limestone

Get your calcium on a plant-based diet

Plant-based picks
Certified vegan

Calcium-fortified oat milk

As much calcium per glass as cow's milk.

Shop fortified oat milk Opens your country’s Amazon store
Certified vegan

Vegan calcium supplement

Plant or mineral calcium with vitamin D, no fish or shell.

Shop vegan calcium Opens your country’s Amazon store
Pantry staple

Calcium-set tofu

One of the richest plant sources of calcium.

Shop calcium-set tofu Opens your country’s Amazon store

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Rules by country

🇺🇸 US FDAApproved
🇪🇺 European UnionApproved
🇨🇦 Health CanadaApproved
CaliforniaNo extra rules

Generally recognized as safe in the US and approved without a daily limit in the EU and Canada. UK and Canadian law require it in most white flour to add calcium.

Daily limit: Experts haven’t set a number because normal food amounts are far below any level of concern.

What is it?

Calcium carbonate is a white mineral powder. In food it adds calcium, balances acidity, keeps powders from clumping and whitens candy coatings. It's the active ingredient in antacids like Tums.

Where it comes from: Mined from limestone or chalk, or made from them. Rarely, it comes from oyster shells or eggshells.

Why it’s in food

  • Adds calcium to plant milks, juice and flour
  • Firms tofu
  • Balances acidity in wine and baked goods
  • Whitens candy and gum coatings

Often found in

Oat, soy and almond milkCalcium-fortified orange juiceBread and flourTofuBreakfast cerealChewing gum and candy

Also listed as: Calcium carbonate, Ground limestone, Precipitated calcium carbonate, Chalk

Health & gut impact

Bone healthBenefit

It's a common, well-absorbed source of calcium, especially when taken with food.

NIH Office of Dietary Supplements, Calcium Fact Sheet

Very high intakeUnder study

Large doses from supplements and antacids can cause constipation or, rarely, too much calcium in the blood. Food levels are well below that.

NIH Office of Dietary Supplements, Calcium Fact Sheet

What can I use instead?

Calcium phosphates

Ratio: To label

Best for: Fortified drinks and baking

Calcium citrate

Ratio: To label

Best for: Supplements taken without food

Related

More acidity regulators:

Citric Acid E330Citric acid (E330) is the sour acid of lemons, made by fermentation. It's safe, vegan, gluten-free and keto-friendly.Generally safeCream of tartar (Potassium bitartrate) E336Cream of tartar (E336) is a natural acid scraped from wine barrels. Bakers use it to whip stable meringue and to make baking powder. It's safe, vegan and fits every diet we check.Generally safeDiphosphates E450Diphosphates (E450), including sodium acid pyrophosphate, make baked goods rise and keep frozen fries from turning gray. They're safe in small amounts, but added phosphates are a concern for kidney health.Use in moderationGlucono-delta-lactone (GDL) E575Glucono-delta-lactone (GDL, E575) is a gentle, slow-acting acid made from glucose. It sets silken tofu and cures salami, and it's considered completely safe.Generally safe

Common questions

Is Calcium carbonate safe?

Generally safe (95/100). Generally recognized as safe in the US and approved without a daily limit in the EU and Canada. UK and Canadian law require it in most white flour to add calcium.

Is Calcium carbonate vegan?

Yes. Almost always mined limestone. Shell-based versions are rare and usually labeled as such.

Is Calcium carbonate gluten-free?

Yes.

Is calcium carbonate in food the same as chalk?

Chemically, yes. Food-grade calcium carbonate is purified to strict limits for lead and other metals.

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Scientific sources & regulatory citations
  • 21 CFR 184.1191 (US FDA)
  • EFSA OpenFoodTox: E170
  • NIH Office of Dietary Supplements, Calcium Fact Sheet

Last checked against FDA, EFSA and Health Canada records: November 2, 2026 · INS 170 · CAS 471-34-1