What Is Cellulose Fiber?

“There’s sawdust in your shredded cheese” is one of the internet’s favorite food scares. The ingredient behind it is cellulose fiber, and the same material makes up the crunch in celery and the bran on a wheat kernel.

The cellulose added to foods is often purified from wood pulp, which is where the rumor starts. Chemically, though, it’s the same fiber you already eat every time you have vegetables, and food safety regulators have looked at it closely.

What is cellulose fiber?

Cellulose is the most common structural material in plants. It’s a long, straight chain of glucose units, the same sugar that makes up starch, linked by bonds that human enzymes can’t break.

Those chains pack tightly together into strong fibers. That’s what gives plant cell walls their shape, and it’s why stalks and husks hold up rather than wilting.

In nutrition terms, cellulose is a classic insoluble fiber. It doesn’t dissolve in water and it doesn’t form a gel the way oat beta-glucan or psyllium do.

Humans aren’t alone in struggling to digest it. Cows and other grazing animals rely on microbes in their specialized stomachs to break cellulose down, a job the human gut does only to a small degree.

Cellulose was among the original seven isolated fibers the FDA recognized in 2016 as dietary fiber for Nutrition Facts labels. That means cellulose added to a food can count toward the fiber grams on the label.

What cellulose does in your gut

Because you can’t digest it, cellulose travels through your stomach and small intestine largely unchanged. It adds volume to what’s moving through without contributing calories the way starch does.

In the large intestine, it does most of its work as bulk. Mayo Clinic describes insoluble fiber as supporting the movement of material through the digestive system and adding stool bulk.

Cellulose is fermented far less than fibers like inulin or pectin. The European Food Safety Authority’s 2018 review states that celluloses aren’t absorbed and are excreted largely intact, though gut bacteria can ferment a small share.

That low fermentation has a practical upside. Cellulose tends to cause less gas than fast-fermenting fibers, which is part of why it’s used in fiber supplements and food products aimed at regularity.

The downside is the flip side of the same fact. Because bacteria use little of it, cellulose does less to feed the gut microbiome than fermentable fibers do.

Cellulose in food: where you’ll find it

Every plant food contains some cellulose, but a few groups carry the most. Mayo Clinic names whole-wheat flour, wheat bran, nuts and beans as good sources of insoluble fiber, along with vegetables such as cauliflower and green beans.

The outer layers of plants are especially rich. Skins, peels, seeds and bran are where much of the tough structural material sits, which is why peeling a potato or refining wheat flour removes a lot of it.

Cellulose in food also shows up as an added ingredient. Food makers use purified forms to keep shredded cheese from clumping, thicken sauces, add fiber to breads and replace some fat in reduced-calorie foods.

Those added forms come in several types, each made for a different job:

• Powdered cellulose: purified cellulose ground into a fine powder, often from wood pulp. It’s used as an anti-caking agent and a fiber source.
• Microcrystalline cellulose: cellulose broken into tiny crystalline particles. It’s common in tablets, including many supplements, and in some low-fat foods.
• Methylcellulose: cellulose chemically modified so it dissolves in cold water and forms a gel when heated. It’s the active ingredient in Citrucel and is used in some plant-based meats.
• Cellulose gum: also called carboxymethylcellulose or CMC. It’s a modified, water-soluble form used as a thickener and emulsifier in ice cream and salad dressings.
• Other modified celluloses: forms such as hydroxypropyl methylcellulose, used in capsules and gluten-free baking.

Plain cellulose and powdered cellulose behave like the insoluble fiber in vegetables. The modified forms, especially cellulose gum, act quite differently, as the next sections show.

Is cellulose safe?

For plain and modified celluloses at normal food levels, regulators say yes. In 2018, the EFSA panel re-evaluated ten types of cellulose used as food additives, from microcrystalline and powdered cellulose to cellulose gum.

The panel concluded there would be no safety concern at the reported uses and use levels. It also saw no need to set a numerical acceptable daily intake, the limit regulators set for additives that pose a risk at higher amounts.

That conclusion rested largely on animal studies and on the fact that celluloses pass through the body without being absorbed. EFSA estimated how much people actually eat and found it well below the levels that caused no harm in long-term animal studies.

The wood-pulp origin doesn’t change the chemistry. Once purified, cellulose from wood and cellulose from celery are the same glucose chains.

Cellulose gum and the gut microbiome

One modified form has drawn closer scrutiny. A 2022 study in Gastroenterology tested whether cellulose gum, a common emulsifier, changes the human gut.

Researchers fed healthy adults a carefully controlled diet free of emulsifiers for 11 days. One group also got 15 g a day of carboxymethylcellulose, far more than most people eat, and the other did not:

The shift into the inner mucus layer matters because that layer normally keeps bacteria away from the gut wall. The authors linked that kind of encroachment with gut inflammation.

The study was very small and short, and the dose was high. It can’t show that normal amounts of cellulose gum cause disease, but it does show that this modified form behaves differently from plain cellulose.

Everyone in the trial was healthy, and only one emulsifier was tested. Researchers still need larger and longer studies, including in people with existing gut conditions.

If you’re working on gut comfort or a sensitive digestive system, our gut health guides explain how different fibers and additives affect the gut.

Cellulose benefits and limits

The main cellulose benefits come from bulk. By holding some water and adding volume to stool, it helps waste move along and can ease mild constipation.

Cellulose-rich foods also tend to be filling and low in calories. They take more chewing too, which naturally slows the pace of a meal. Vegetables and whole grains carry cellulose alongside other fibers and minerals that the purified powder doesn’t provide.

Its limits are worth knowing. Because it’s fermented so little, cellulose does less than soluble or prebiotic fibers for cholesterol or gut bacteria.

That’s why a mix of fiber types matters more than any single one. Cellulose handles bulk, while fibers like oat beta-glucan and inulin take care of cholesterol and feeding the microbiome.

To see how cellulose-rich foods add up across your day, our fiber calculator gives you a personal figure to work from.

Cellulose vs other common fibers

Compared with psyllium, cellulose is drier and less gel-forming. Psyllium holds a lot of water in a gel, while cellulose adds bulk in a firmer, more particle-like way.

Compared with wheat bran, the difference is mostly packaging. Wheat bran is rich in cellulose but also carries arabinoxylan and other fibers, plus minerals, so it does more than purified cellulose alone.

Compared with methylcellulose, plain cellulose doesn’t dissolve. Methylcellulose has been modified to dissolve and form a gel, which is why it behaves more like a soluble fiber supplement.

Compared with inulin, cellulose is the slow, steady type. Inulin ferments quickly and feeds bacteria, which can mean more gas, while cellulose passes through with less fuss.

If you’re comparing cellulose-based supplements with psyllium or other powders, our supplement comparisons lay out the main differences.

Who should go slow with cellulose

Most people tolerate cellulose well, and it causes less gas than many fibers. Adding a lot of bran or raw vegetables quickly can still leave you feeling bloated or briefly more irregular. Most of that settles within a few days as your gut adjusts.

People with a narrowed bowel or recovering from gut surgery are sometimes told to limit very fibrous foods for a while. Anyone in that situation should follow the diet their care team has set.

For everyone else, the usual approach works. Increase cellulose-rich foods over a week or two, and drink water as your fiber goes up, since insoluble fiber works best with fluid.

One change to try this week

Leave the skins on. This week, cook potatoes or carrots with the peel intact, or swap white flour for whole-wheat in one recipe.

Those outer layers are where much of a plant’s cellulose lives. It’s the simplest way to add this kind of fiber without buying anything new.

And if you buy pre-shredded cheese, there’s no need to avoid it on cellulose grounds. Just don’t count on the anti-caking powder as a meaningful fiber source.

Sources

• European Food Safety Authority Panel on Food Additives and Nutrient Sources Added to Food. “Re-evaluation of Celluloses E 460(i), E 460(ii), E 461, E 462, E 463, E 464, E 465, E 466, E 468 and E 469 as Food Additives.” EFSA Journal. 2018. doi.org
• Chassaing B, Compher C, et al. “Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome.” Gastroenterology. 2022. pure.psu.edu
• Mayo Clinic Staff. “Dietary Fiber: Essential for a Healthy Diet.” Mayo Clinic. 2025. mayoclinic.org
• U.S. Food and Drug Administration. “Questions and Answers on Dietary Fiber.” 2024. fda.gov