E170 — Calcium carbonate
E170 (Calcium carbonate), a color, is rated "watch": fine in moderation. Ground limestone or chalk. Used as a white color, mineral source, and antacid. Same compound as a calcium supplement tablet.
What is Calcium carbonate?
Ground limestone or chalk. Used as a white color, anti-caking agent, and calcium fortification source in flour, breads, supplements, and chewable antacids.
What does it do to the body?
Provides calcium that your body uses normally. Very large doses can cause constipation or, very rarely, milk-alkali syndrome; food-level use is well below those amounts.
What regulators say
EFSA and the FDA both approve it without a specific acceptable daily intake.
Risk rating: Watch
Mixed evidence or a specific concern (gut, allergy, or contested safety data). Not alarming, but worth keeping an eye on rather than eating without limit.