E466 — Carboxymethyl cellulose
E466 (Carboxymethyl cellulose), a thickener, is rated "avoid": worth avoiding. A modified cellulose emulsifier and thickener, also called cellulose gum. In a 2022 randomised human feeding trial it disturbed the gut microbiome and cut microbial diversity in healthy adults after 11 days.
What is Carboxymethyl cellulose?
A modified cellulose emulsifier and thickener, also called cellulose gum. Common in ice cream, salad dressings, gluten-free bakery, sauces, drink powders, and toothpaste.
What does it do to the body?
Your body does not absorb it — the concern is what it does on the way through. A 2022 randomised controlled-feeding trial (Chassaing et al., Gastroenterology) fed healthy adults CMC for 11 days and found reduced gut bacterial diversity, lower short-chain fatty acids, and modestly more post-meal abdominal discomfort. In 2 of the 7 CMC subjects, bacteria moved into the mucus layer that normally keeps them off the gut wall — an early marker of inflammation. Mouse studies link emulsifiers like CMC to intestinal inflammation. Long-term effects in people are not settled; the signal matters most if you have IBD or another inflammatory gut condition.
What regulators say
EFSA reviewed the celluloses in 2018 and did not set a numerical limit, and it revisited E466 in 2022: it acknowledged the reported changes in microbiota diversity but concluded their meaning is not yet clear, and it could not fully assess the safety of use in foods for infants and young children. So it stays permitted in the EU, and the FDA treats it as GRAS — but the human microbiome finding is unresolved rather than dismissed.
Risk rating: Avoid
Known or suspected to cause harm: a substance EFSA or another regulator has flagged, or one restricted in some jurisdictions. Best kept out of a regular diet.
Source: Chassaing et al. 2022 — randomised controlled-feeding study, Gastroenterology ↗