Understanding the Side Effects of Microcrystalline Cellulose in Humans

January 6, 2026 •

5 min read

Microcrystalline cellulose (MCC) is generally recognized as safe (GRAS) by the U.S. Food and Drug Administration when used in normal quantities. As an insoluble dietary fiber, it is a common additive in processed foods and supplements, yet some people experience side effects, particularly related to the digestive system.

Quick Summary

Microcrystalline cellulose can cause digestive issues like bloating, gas, and constipation, especially when consumed in high amounts. Allergic reactions, though rare, are also possible in sensitive individuals. It is indigestible by humans and generally considered safe at typical intake levels.

Key Points

Digestive Upset: The most common side effects of microcrystalline cellulose are digestive issues like bloating, gas, and cramping, especially when consumed in large amounts, similar to other forms of fiber.
Allergic Reactions Are Rare: While MCC is generally considered hypoallergenic, rare allergic reactions, including skin rashes, respiratory problems, and GI distress, have been reported in sensitive individuals.
Fiber-Related Symptoms: These side effects often mimic those from excessive fiber intake, including constipation or diarrhea, and can be mitigated by ensuring adequate hydration.
Nutrient Absorption Impact: Very high doses of MCC might potentially interfere with the absorption of certain minerals or medications, though this is not a concern with typical consumption levels.
Safe in Moderation: Regulatory bodies like the FDA classify MCC as generally recognized as safe (GRAS), and typical intake as an additive is not considered hazardous to human health.
Consult a Doctor: Individuals with existing digestive conditions or those taking medications should consult a healthcare professional before significantly increasing their MCC intake via supplements.

What is Microcrystalline Cellulose?

Microcrystalline cellulose (MCC) is a refined, purified form of cellulose, the most abundant organic polymer found in plant cell walls. It is manufactured from fibrous plant material, most commonly wood pulp, through acid hydrolysis. The resulting product is a fine, crystalline powder that is tasteless, odorless, and insoluble in water. In the pharmaceutical industry, MCC is a highly valued excipient, or inactive ingredient, used as a binder, filler, and disintegrant in tablets and capsules due to its excellent compressibility. In the food industry, it serves as an anti-caking agent, texturizer, emulsifier, and fat substitute, and is also added to boost the fiber content of some products. As it is an insoluble fiber, the human body cannot digest or absorb MCC, and it passes through the gastrointestinal tract largely unchanged.

Common Digestive Side Effects

Since microcrystalline cellulose is a form of insoluble fiber, the most common side effects reported by humans are related to the digestive system and are typically a result of consuming large amounts. These symptoms are similar to those experienced when increasing dietary fiber intake from any source too quickly.

The following digestive issues may occur:

Gas and Bloating: As insoluble fiber, MCC adds bulk to stool, and excessive amounts can lead to increased gas production and a feeling of abdominal fullness or bloating.
Constipation: Paradoxically, while fiber generally helps with bowel regularity, a sudden and significant increase in insoluble fiber intake without a corresponding increase in fluid can cause constipation. The added bulk can create a blockage if not enough water is present to help it move through the system.
Diarrhea or Loose Stools: Conversely, some individuals may experience looser bowel movements, especially with a sudden jump in intake.
Stomach Cramps: Intestinal discomfort and cramping can be associated with gas and bloating caused by high fiber consumption.

These symptoms are often mild and can be managed by gradually increasing intake, ensuring adequate hydration, and exercising. For most people, normal consumption as an additive in foods or supplements poses no issue.

Allergic and Hypersensitivity Reactions

While microcrystalline cellulose is considered hypoallergenic for most people, rare cases of allergic reactions have been reported. These reactions are not caused by the MCC itself but rather by the individual's immune system's response to it.

Symptoms of a cellulose allergy may include:

Skin reactions: Rashes, itching, or hives.
Respiratory issues: Wheezing, coughing, or difficulty breathing in more severe cases.
Gastrointestinal distress: Severe versions of the typical digestive side effects.
Anaphylaxis: In extremely rare instances, a life-threatening anaphylactic reaction could occur, requiring immediate medical attention.

Some individuals with Mast Cell Activation Syndrome (MCAS) may be particularly sensitive to excipients like MCC, reacting to the “inactive” ingredients in their medications or supplements. If any of these symptoms appear after consuming a product containing MCC, a healthcare provider should be consulted.

Impact on Nutrient Absorption

Excessive intake of any type of fiber, including MCC, can potentially interfere with the absorption of certain nutrients and medications. Fiber can bind to minerals like calcium and iron, potentially reducing their bioavailability. Similarly, fiber supplements may interfere with the absorption of certain drugs, such as aspirin and seizure medications. This is a concern primarily for individuals taking high-dose fiber supplements or consuming unusually large quantities of MCC, not for typical dietary exposure.

Safety Regulations and Considerations

The U.S. FDA’s status of GRAS for MCC is supported by various regulatory bodies worldwide, including the European Food Safety Authority (EFSA). The conclusion of these bodies is that MCC is generally safe at the levels currently used in food and pharmaceutical products. Studies have shown that ingesting up to 30 grams of MCC per day had no adverse effects beyond increased fecal output in human subjects. It is important to note that the long-term health effects of high and sustained consumption of modified fibers are still being researched.

Managing and Avoiding Side Effects

To minimize or avoid potential side effects from microcrystalline cellulose, consider the following best practices:

Gradual Increase: If taking fiber supplements containing MCC, start with a low dose and increase gradually to allow your digestive system to adjust.
Stay Hydrated: Drink plenty of water throughout the day, especially when increasing fiber intake, to help the fiber move smoothly through your digestive tract and prevent constipation.
Prioritize Whole Foods: While MCC is a source of fiber, getting fiber from whole plant foods like fruits, vegetables, and grains offers a wider range of beneficial nutrients.
Consult a Professional: If you have an inflammatory bowel disease (IBD) or other digestive condition, or if you take medication, consult a healthcare professional before taking supplements high in MCC.

Microcrystalline Cellulose vs. Alternative Excipients


Feature	Microcrystalline Cellulose (MCC)	Lactose	Starch	Dicalcium Phosphate (DCP)
Origin	Purified wood pulp/cotton	Milk	Corn, potato, wheat	Mineral
Primary Function	Binder, filler, disintegrant	Filler, binder	Disintegrant, filler	Filler, binder
Compressibility	Excellent	Good	Fair	Very Good
Compatibility	Broad, chemically inert	Good; potential issues with lactose intolerance	Fair; potential for moisture issues	Good; can be abrasive
Safety	GRAS (generally safe)	Potential for lactose intolerance	Generally safe	Generally safe
Best Use Case	Versatile for oral dosage forms	Cost-effective filler for many tablets	Promotes rapid tablet breakup	Sturdy binder, affordable

Conclusion

Microcrystalline cellulose is a widely used and highly versatile additive that is generally considered safe for human consumption in the amounts typically encountered in food and medications. The side effects most people experience are digestive in nature, such as gas, bloating, and changes in bowel habits, and are almost always a consequence of high or rapidly increased intake of this insoluble fiber. These symptoms can often be alleviated with proper hydration and by adjusting intake. While rare, allergic reactions are a possibility for some sensitive individuals, and interference with nutrient or drug absorption can occur with very high doses. As with any dietary component, moderation and paying attention to your body's response are key. For individuals with existing gastrointestinal issues or those on specific medications, consulting a healthcare provider is recommended for peace of mind. For more on the regulatory status of MCC, you can find information via the FDA GRAS status information.

Frequently Asked Questions

Microcrystalline cellulose is generally not considered bad for you. It is classified as Generally Recognized As Safe (GRAS) by the FDA and is an inert, indigestible fiber. Side effects are typically minor digestive discomforts that occur when very high amounts are consumed.

Consuming too much microcrystalline cellulose can lead to digestive side effects, including bloating, gas, stomach cramps, constipation, or diarrhea, due to its high fiber content. Increasing intake gradually and drinking plenty of water can help prevent these symptoms.

While it is rare, it is possible for some people to have an allergic reaction to microcrystalline cellulose. Symptoms can include skin rashes, itching, or respiratory issues. If you suspect an allergy, you should seek medical advice.

Microcrystalline cellulose is widely used in pharmaceuticals as a binder and filler for tablets and capsules. In the food industry, it is found in products like shredded cheese, dressings, ice cream, and diet foods as a texturizer, anti-caking agent, and fat substitute.

Microcrystalline cellulose is produced from high-grade plant fiber, typically wood pulp. The fiber is subjected to controlled acid hydrolysis, which breaks down the cellulose into crystalline fragments. These fragments are then purified and dried into a fine powder.

In very high doses, microcrystalline cellulose, like other fibers, can potentially reduce the absorption of certain minerals. For most people consuming it in typical food or supplement amounts, this is not a significant concern.

To avoid digestive discomfort, you can increase your intake of products containing MCC gradually and make sure to drink plenty of water. Choosing whole food sources of fiber over supplements can also be beneficial.

Individuals with inflammatory bowel disease (IBD), those who are particularly sensitive to fiber, and people taking certain medications should be cautious with high MCC intake. It is best for these individuals to consult a doctor.