What it is
Refined plant pulp, chemically modified into a gum that bulks, binds, and thickens.
Why your biology objects
Carboxymethylcellulose is a synthetic emulsifier/thickener, and it keeps the same bad company as polysorbate in the gut studies — mucus thinning and microbiome disruption in mice and a recent human pilot. Modified beyond the inert fiber it started as.