Calcium carbonate
A naturally occurring mineral (chalk) added to food as a white colourant, acidity buffer, anti-caking agent, and calcium fortifier.
E170 is not pure calcium carbonate in all forms. The mineral used in food production can carry aluminium as an unavoidable impurity. EFSA found in 2023 that aluminium from E170 could push some population groups above the tolerable weekly intake for aluminium, particularly when E170 is used heavily across multiple foods. Regulators have called for stricter aluminium limits in E170 specifications.
What is it?
Calcium carbonate (CaCO3) is the main mineral in chalk, limestone and marble. The food-grade version is either ground from naturally occurring limestone or produced synthetically by precipitation. It is a white, odourless, virtually insoluble powder.
What does it do?
As a colourant it imparts bright whiteness to surfaces and coatings. As an acidity regulator it neutralises excess acid, buffering pH without dramatically altering flavour. As an anti-caking agent it absorbs moisture to keep powdered foods free-flowing. As a calcium fortifier it raises the calcium content of foods where the mineral is added by manufacturers or required by law.
Where you will see it
Added by law to all non-wholemeal wheat flour milled in the UK under the Bread and Flour Regulations, meaning it appears in the vast majority of everyday bread and baked goods. Also used in breakfast cereals, plant-based milks (oat, soy, almond), tofu, chewing gum, sugar confectionery coatings, cake decorations, dietary supplements, and ripened cheese rinds. On a label it appears as calcium carbonate or E170.
What the science says
Aluminium impurity in E170
Calcium carbonate produced from limestone naturally contains traces of aluminium that cannot be fully removed. EFSA's 2023 re-evaluation found that the aluminium carried in E170 can account for 50 to 100 percent of the tolerable weekly intake for aluminium in some population groups. Under the maximum aluminium levels proposed by industry, certain groups could exceed the TWI by around fourfold. EFSA called for new, lower maximum aluminium limits to be written into the product specifications for E170.
Aluminium intake from E170 as a food additive could account for 50 to 100 percent of the tolerable weekly intake of 1 mg aluminium per kilogram of body weight per week, and could substantially exceed that TWI in some population groups at the maximum measured levels.
The unavoidable presence of aluminium in E170 is of concern and should be addressed through stricter specifications.
Calcium carbonate itself
Both EFSA's 2011 and 2023 evaluations concluded that calcium carbonate at the quantities used as a food additive raises no safety concern for any age group, including infants under 16 weeks. No numerical acceptable daily intake has been set because the substance behaves like a normal dietary mineral at food-use levels. The calcium contributed by E170 in food is a small fraction of total dietary calcium intake.
The EFSA ANS Panel concluded there is no need for a numerical ADI for calcium carbonate and agreed with the group ADI 'not specified' when used as a food additive.
Exposure to calcium from calcium carbonate as a food additive does not raise concerns; it contributes only a small part to overall calcium dietary exposure.
Mandatory UK flour fortification
Since 1942, UK law has required calcium carbonate to be added to all non-wholemeal wheat flour. This was introduced to protect public calcium intake when wartime diets changed. Updated Bread and Flour Regulations maintain the requirement, and in 2024 the minimum level was increased. The calcium carbonate used must meet specific purity criteria, and supply of compliant material currently comes from a single quarry in France.
The Bread and Flour Regulations require calcium carbonate to be added to all non-wholemeal wheat flour produced at mills making 500 tonnes or more per year; this requirement has been in place since 1942.
Where it stands with the regulators
Who should be careful
People with hypercalcaemia (raised blood calcium) or a history of calcium-containing kidney stones should monitor their total calcium intake across all sources, including fortified foods. This applies mainly to high-dose supplement use rather than E170 in everyday food products. There is no specific label trigger for E170 beyond its standard declaration as calcium carbonate or E170 in the ingredients list.
The honest read
The additive itself is chalk, a mineral humans have been consuming incidentally through food and water for as long as people have eaten. EFSA has reviewed it twice and found no concern with calcium carbonate at food-use levels. The open question identified in 2023 is about what comes with the mineral, not the mineral itself: aluminium occurs naturally in limestone and cannot be fully removed. Regulators flagged this and called for tighter impurity limits in the chalk used for food. Whether those stricter limits are yet written into law is something the regulator is still working through. The scale of any aluminium exposure from E170 depends on how much chalk is in a given food and how widely a person eats foods that use it, which makes this harder to pin down than a straightforward additive concern.
Related additives
Common questions
Is E170 banned in the UK?
No. Calcium carbonate (E170) is approved for use in the UK under the UK FSA approved-additives list and retained EU food additive law. It is not only permitted but is legally required to be added to most non-wholemeal wheat flour sold in the UK.
Why did EFSA flag a concern about E170 in 2023?
EFSA's concern was not about calcium carbonate itself, but about aluminium that occurs naturally in the limestone used to produce E170. The panel found that in some population groups, the aluminium carried in E170 could push weekly aluminium intake above the tolerable limit. EFSA called for stricter maximum aluminium levels in the purity specifications for E170.
What foods contain E170?
Most everyday bread and baked goods in the UK contain E170 because it is legally required in non-wholemeal wheat flour. It is also added to many breakfast cereals, plant-based milk alternatives, chewing gum, sugar confectionery coatings, and dietary supplements. On pack it appears as calcium carbonate or E170.
Is E170 vegan?
It depends on the source. Most food-grade calcium carbonate comes from quarried limestone, which is vegan. However, calcium carbonate is also produced from oyster shells, eggshells, and other animal-derived shells, which is not. Manufacturers are not required to declare which source they use, so it is not always possible to confirm the origin from the label alone.
Sources
- EFSA FAF Panel: Re-evaluation of calcium carbonate (E 170) as a food additive in foods for infants below 16 weeks of age and follow-up of its re-evaluation as food additive for uses in foods for all population groups. EFSA Journal 2023;21(7):8106
- PubMed: EFSA 2023 re-evaluation of E170
- PMC full text: EFSA 2023 re-evaluation of E170
- UK Food Standards Agency: Approved additives and E numbers
- UK FSA regulated products database: E-170
- Real Bread Campaign: Flour fortification chalk supply risk to the UK food system (December 2024)
- EFSA ANS Panel: Scientific Opinion on re-evaluation of calcium carbonate (E 170) as a food additive. EFSA Journal 2011;9(7):2318
- UK Bread and Flour Regulations 1998 (as amended), DEFRA
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