"Is carboxymethyl cellulose the same as cellulose gum?"

"Yes. 'Cellulose gum' is the common name used on US food labels. 'Carboxymethyl cellulose' or 'CMC' is the technical name. 'Sodium carboxymethylcellulose' or 'sodium CMC' specifies the sodium salt form, which is what's actually used in food. The EU designation is E466."

"How is CMC different from regular cellulose?"

"Native cellulose is insoluble in water — it's the structural fiber in plant cell walls. Carboxymethyl cellulose is made by reacting cellulose with monochloroacetic acid, which attaches carboxymethyl groups (-CH2COOH) to the cellulose backbone. These groups carry a negative charge in solution, causing the chains to repel each other and allowing CMC to dissolve and form a viscous solution. This is why CMC can function as an emulsifier and thickener while native cellulose cannot."

"What's the typical dietary intake of CMC?"

"Estimated daily intake from food is roughly 100-250 mg per day for most consumers, based on FDA and EFSA estimates from food consumption surveys. The 2022 Chassaing human study used 15 grams per day — about 60-150 times the estimated average dietary exposure. The study was designed to test effects at a dose above average but within what very heavy processed food consumers might approach."

"Should I be concerned about CMC if I have IBD?"

"The Chassaing research group's work specifically examined links between emulsifiers and inflammatory bowel conditions. If you have Crohn's disease or ulcerative colitis, discussing dietary emulsifier intake with your gastroenterologist is reasonable given the mechanistic evidence. The research doesn't prove CMC causes IBD, but the biological plausibility of the emulsifier-gut barrier connection is higher for people with existing IBD."

Carboxymethyl Cellulose: The Emulsifier Under the Microbiome Microscope

Quick Answer

Carboxymethyl cellulose (CMC, also called cellulose gum) is FDA-approved. A 2022 randomized human trial found gut microbiome changes at 15g per day — far above typical dietary exposure of about 250mg per day. Current regulatory bodies haven't changed safety assessments, but this additive has more human microbiome data than most, and the findings are worth taking seriously.

The Science

Carboxymethyl cellulose sits at the intersection of two things: ubiquity and emerging science. It’s in ice cream, salad dressings, low-fat dairy, processed meats, and toothpaste. And it’s now the subject of the most detailed human microbiome study done on any food emulsifier.

The results are not alarming. They’re also not nothing.

What It Is

Carboxymethyl cellulose (CMC, E466) is made by chemically modifying cellulose — the insoluble structural fiber in plant cell walls. Treating cellulose with monochloroacetic acid in the presence of sodium hydroxide attaches carboxymethyl groups to the glucose units that make up the cellulose backbone.

The modification converts an insoluble structural fiber into a water-soluble gum that dissolves readily to form a viscous solution. The degree of substitution (DS) — how many hydroxyl groups have been replaced — determines the product’s viscosity and solubility. Higher DS means better solubility.

The resulting sodium carboxymethylcellulose is what appears in food. It’s white, odorless, and tasteless. It functions as a thickener, emulsifier, and stabilizer.

What It Does in Food

Ice cream is CMC’s primary application. It prevents ice crystal growth during storage and freeze-thaw cycles, which keeps ice cream scoopable after extended freezer time. It also helps maintain the creamy texture that marketing photos promise.

In low-fat dairy products (reduced-fat cream cheese, diet yogurt), CMC compensates for the mouthfeel and texture that fat normally provides. Remove fat from a dairy product and it becomes thin and watery; add CMC and some of that body returns.

In salad dressings, it stabilizes emulsions and prevents oil separation. In processed meats, it binds water. In gluten-free baked goods, it provides structure similarly to how xanthan gum does.

It’s also non-food: CMC is widely used in toothpaste (as a binder and texture agent), pharmaceutical tablets (as a binder), and personal care products.

The 2015 Mouse Study

The key paper is the 2015 Chassaing et al. study in Nature (the same study examined in the polysorbate 80 article). That study tested both polysorbate 80 and CMC in mice.

CMC at 1% in drinking water produced:

Altered gut microbiota composition
Thinning of the mucus layer protecting the gut epithelium
Increased bacterial translocation toward the gut wall
Low-grade intestinal inflammation
Metabolic syndrome markers in some mouse strains

The same concerns about high dose and mouse-to-human extrapolation apply as with polysorbate 80. But a crucial follow-up happened with CMC that didn’t happen as directly for polysorbate 80.

The 2022 Human Trial: A Different Level of Evidence

In 2022, the same Chassaing research group published a randomized controlled feeding trial in Gastroenterology — this time in humans.

16 healthy adults participated in a two-week in-patient feeding study. They were randomly assigned to either a control diet or the same diet supplemented with 15 grams of CMC per day. They lived in a clinical research unit and all food was controlled and provided.

Results after 11 days:

Significant reductions in gut microbiota diversity in the CMC group
Changes in the abundance of specific bacterial species
Alterations in fecal metabolite profiles, including reduced production of short-chain fatty acids (which are beneficial products of gut bacteria)
Mild increases in gut permeability markers in some subjects
Some participants developed subclinical intestinal inflammation

This is different from the mouse data. It’s actual humans, controlled feeding, randomized design.

The Dose Context

The 15g per day dose is not typical. Most people consume an estimated 100-250 mg per day from dietary sources. The study dose is 60 to 150 times higher.

Why study at 15g? The researchers wanted to detect mechanistic effects that might be too subtle to measure at lower doses. They also argued that heavy processed food consumers might approach 1-2 grams per day in their highest estimates, and the dose-response relationship between low and high exposures isn’t fully established.

The dose doesn’t make the study irrelevant — but it does limit conclusions about real-world dietary exposure. A study showing effects at 15g/day cannot be directly extrapolated to say that 250mg/day causes the same effects in proportion. Biology doesn’t always scale linearly.

What Regulatory Bodies Said

The FDA has not changed its GRAS status for CMC. EFSA has not changed its approval. Both agencies have indicated they are aware of the emerging microbiome research and that it represents a developing area of science rather than an established safety finding.

This is the regulatory way of saying: we’re watching, we haven’t been convinced to act, but this isn’t dismissed either.

CMC and IBD: what the mechanistic research suggests

The biological mechanism proposed by the Chassaing research group: emulsifiers with detergent-like properties (both polysorbate 80 and CMC are surfactants) may disrupt the protective mucus layer of the gut. This mucus layer normally maintains a physical separation between gut bacteria and the epithelial cells lining the intestine. When bacteria contact epithelial cells directly, inflammatory signaling can increase.

Inflammatory bowel disease (IBD) — both Crohn’s disease and ulcerative colitis — involves chronic inflammation at the gut-bacteria interface. The hypothesis is that emulsifiers might promote or exacerbate conditions that predispose to IBD, particularly in genetically susceptible individuals.

A 2017 follow-up study by Viennois et al. found that low-grade chronic intestinal inflammation induced by emulsifiers in mice promoted colon carcinogenesis — tumor formation — in a cancer model. The mechanistic chain: emulsifiers promote microbiome disruption, which promotes chronic low-grade inflammation, which increases cancer risk over time.

None of this has been demonstrated in humans as a causal chain. But it’s a plausible biological mechanism that makes the human trial findings more significant than they might otherwise be.

Where CMC Stands

CMC occupies a different position than polysorbate 80 in the current evidence landscape. The 2022 human trial gives it one of the strongest microbiome effect datasets of any food emulsifier — even if the dose used was well above normal dietary intake.

The verdict remains safe because current evidence doesn’t establish that dietary-level CMC causes harm in healthy humans. But the research is more developed for CMC than for most emulsifiers, and the findings warrant ongoing monitoring.

If you have inflammatory bowel disease, significant gut dysbiosis, or other gut-related health concerns, the mechanistic case for reducing processed food intake — which includes reducing CMC exposure — is stronger than for the average healthy consumer.

What This Means for You

CMC is in ice cream, dairy products, and many processed foods. At typical dietary amounts, the evidence doesn't support cutting it out. If you have inflammatory bowel conditions or known gut dysbiosis, the 2022 data is a reasonable basis for discussing dietary changes with your doctor. People eating mostly whole, unprocessed foods already have low CMC exposure.