Let me start off by saying, I’m not a qualified chemist, and the research I’ve done into this has uncovered some inconsistencies that have puzzled and concerned me. This is why I want to open the conversation, and together we can consider what Carboxymethylcellulose is.
Other than it looking like the final impassible challenge in a high school spelling bee, it is quite a widely used substance in many consumable products.
Also known as CMC, which is a heck of a lot easier to get your tongue around, it is often found in manufactured foods and personal care products, like toothpaste. Talk about getting your tongue around it! Or, is it more like it’s getting around your tongue?
Anyhow, come with me as we take a closer look at Carboxymethylcellulose (CMC) and ponder the thought ‘is it safe?’
Table of Contents
What is Carboxymethylcellulose?
It is a food additive that is generally considered to be safe for consumption by the US Food and Drug Administration (FDA) and other regulatory agencies worldwide. It is ‘generally recognised as safe’ (GRAS) by these authorities. [1, 2]
One thing about these ‘approvals’ by Regulators that I think is worth keeping in mind is that they are for Sodium Carboxymethylcellulose (CMC-Na) and not Carboxymethylcellulose (CMC). Just keep that in your back pocket for now, we will come back to it.
Now, research shows us that some people may be allergic to CMC or may have an intolerance to it. Additionally, CMC can cause some digestive symptoms such as gas, bloating, and diarrhea if consumed in large amounts.
Like with other products that trigger allergic reactions, people with known allergies or intolerances to CMC should avoid it.
Is CMC the same thing as CMC-Na?
This is where the waters tend to become a little muddied. It seems that many are taking the FDA’s approval of one thing and transposing it to another. And, according to PubChem records, CMC and CMC-Na are not considered to be synonyms of each other. Let me explain.
Carboxymethylcellulose (CMC) and Carboxymethylcellulose sodium (CMC-Na) are similar, but not exactly the same. Both are derivatives of cellulose, which is a natural polymer found in plant cell walls. 
CMC is a cellulose derivative that has been modified by the addition of carboxymethyl groups. It is a white, odorless, tasteless powder that is insoluble in water and is used as a thickener, emulsifier, and stabiliser in food and other industries. 
CMC-Na on the other hand, sometimes referred to as Sodium carboxymethylcellulose, is a cellulose derivative that has been modified by the addition of carboxymethyl groups, and then reacted with sodium hydroxide. It is a white, water-soluble powder that is used as a thickener, emulsifier, and stabiliser in food, pharmaceuticals, and other industries. 
The records on the FDA’s website point to Sodium carboxymethylcellulose (CMC-Na) being the approved substance, and not Carboxymethylcellulose (CMC). This may sound pedantic, but there are differences between the two. [1, 3]
A key point I want to draw your attention to here is the water-soluble nature of CMC-Na. This is what was described as being used in the studies referenced by the LA Times, yet in their article, they call it CMC. To me, this is just another example of confusion arising from perceived interchangeability. 
The same can be said for how it has been reported in National Geographic. In an article published a year after the LA Times article, National Geographic cited the same study with the same tone of caution. [7, 12]
This may sound like splitting hairs, or arguing that CMC and CMC-Na are safe and fine to use, however, that’s not what I’m doing here.
If something (CMC-Na) is more soluble in one form compared to another (CMC), then I would suggest that it is going to behave differently once it gets into your body.
And that’s not considering the probable complexities that come with this substance being known by more than 200 synonyms according to the Chemical Book listing for the CAS number 9004-32-4 is assigned to CMC. 
Considering Terminologies Used in Studies
Once we have been able to nail down what is what, I think we’ll be on a clearer path. Some of the studies I’ve looked at showed some of these inconsistencies.
The ambiguity of the references is prolific, regardless of their commonalities in applications. A number of studies refer to the substance as CMC, yet their molecular diagram illustrations and descriptions align with CMC-Na. 
Referred to in this study as CMC, but also as sodium carboxymethyl cellulose, the Researchers expressed concerns with the potential for CMC-Na to trigger obesity. 
Meanwhile, the ambiguity of the use of CMC or CMC-Na in this study still provides for a question mark in my opinion. I am assuming that the increased sodium excretion in the urine of the mice suggests that this was CMC-Na. The Researchers in this study concluded that there are no noteworthy risks with CMC. 
Ok, for now, let’s park the CMC vs CMC-Na part of the conversation and assume that the interchangeability of names is implied.
Where does CMC come from?
The manufacturing process for CMC involves treating cellulose, which is a natural polymer found in plant cell walls, with chemicals to introduce carboxymethyl groups (-CH2COOH) onto the cellulose molecule. This process is called carboxymethylation. 
First, cellulose is dissolved in an alkali solution, such as sodium hydroxide. Then, the cellulose solution is mixed with monochloroacetic acid (MCA) and more sodium hydroxide, under controlled temperature and pressure. This chemical reaction causes the formation of carboxymethyl groups on the cellulose molecule, creating CMC.
What is CMC used in?
CMC is considered to be GRAS and a versatile food additive that is used in a wide variety of products, it is commonly used as a:
- Emulsifier, and
This is the most common application of CMC is in food and beverages. Some examples of products that may contain CMC may include:
- Salad dressings and sauces
- Ice cream and frozen desserts
- Chewing gum
- Bread and baked goods
- Confections and candy
- Dairy products such as cheese and whipped cream
- Beverages such as juice and milk-based drinks
- Meat and poultry products
- Vegetarian and vegan products, and
- Cosmetics and personal care products.
There has been interesting discussion around the scope of what is a thickener, emulsifier, and stabiliser with regard to CMC. This takes an interesting turn in a letter to the Editor of Gastroenterology, a publication of the American Gastroenterological Association pertaining to a previous study. 
The Researchers who submitted this letter to the Editor also raise points pertaining to the effects on the distribution and composition of the subject’s microbiota and subsequent alterations to function. This suggests that CMC may be effectively reprogramming your good gut bacteria and causing them to turn on a weakening mucosal lining. 
CMC is also be used in other industries such as:
- Oil and Gas
- Ceramics, and
CMC is certainly a versatile material that can be used in a variety of industries beyond food and beverages. Here’s how it’s typically used in the previously stated industries:
- CMC is commonly used as a binder, disintegrant, and lubricant in tablet and capsule formulations, and also as a suspending agent and thickener in liquid preparations.
- Oil and gas
- CMC is used as a viscosifier, often called ‘muds’ in the drilling industry, and is a material that increases the viscosity of fluids. In drilling, it helps to lift debris and sediment up with the water in a thick fluid to help stabilise the borehole and prevent blockages of drill strings, and a collapse of the wellbore.
- CMC can be used as a binder and plasticiser in the preparation of ceramic pastes and glazes, which help to improve the processability and the mechanical properties of the final product.
- CMC is used as a binder and thickener in construction materials such as adhesives, mortars, and plasters. It can help to improve the workability, adhesion, and water resistance of these materials.
I find myself pondering the question ‘What are the differences between these two when it comes to ingesting them, and digestion? Is one safer than the other?’
For now, the best that can be done is to consider the research and apply what I like to call a measured amount of caution.
5 CMC Health Risks
One study into CMC suggested that the disturbance of the host’s microbiota may potentially result in colon carcinogenesis arising from the low-grade inflammation of the gut. 
The potential for CMC to result in the onset of leaky gut as a result of these disturbances was also explored 
The increased instances of metabolic syndrome/obesity and a number of chronic inflammatory conditions connected to the data observed in connection with the consumption of products containing CMC were explored in a study conducted in 2015. Aspects of biological alteration that were considered included the composition of microbiota, their encroachment, and the increase in pro-inflammatory potential. 
On the other hand, another study considered the probability of the effects of CMC directly on the host which then influenced the microbiota and the health of the broader gut environment. 
When you consider the quote by Hippocrates “All disease begins in the gut” and then ponder the results of this study which uncovered social anxiety-centric behavioral changes in mice, you begin to see things a little differently. The mice who were administered CMC along with polysorbate 80 displayed behaviours that were influenced by the gut-brain axis. The science behind the connections between the gut and mental health is not a new thing. [21, 22]
Even though the comments in one particular study suggest that the levels of CMC used are much lower than what is in the average diet. The Authors even said that human studies need to be completed before assuming any deleterious effects of CMC (note: they did not state CMC-Na but CMC) on humans. 
I struggle to see these comments as a form of endorsement of the safety of CMC. But hey, that’s just me.
Is Carboxymethylcellulose Harmful?
CMC can be found in various foods and personal care products. It is classified by the FDA as generally considered safe and there are limited studies to suggest that in the small quantities that it is used that it has been proven harmful.
This having been said, larger quantities of CMC have been linked to various health concerns.
Is Carboxymethylcellulose Safe in Food?
CMC is generally considered to be safe by various Regulators and Authorities.
However, more and more Researchers are coming forward with results from studies that suggest that it may not be safe in higher quantities.
Is Carboxymethylcellulose Artificial Tears?
CMC is not itself artificial tears. It is an ingredient that is used in some artificial tears products. CMC is used as a thickening and viscosity-increasing agent in some artificial tears products, as it helps to keep the drops in the eye for a longer period of time.
However, other ingredients may also be used such as Polyethylene glycol (PEG) or Propylene glycol (PG).
What is Another Name for Carboxymethylcellulose?
Other names for Carboxymethylcellulose include:
• Sodium Carboxymethyl Cellulose (CMC)
• Cellulose Gum
• Cellulose Gel
• Cellulose Gum, Sodium Salt
• Cellulose, Carboxymethyl Ether
• Cellulose, Sodium Salt, Carboxymethyl Ether
• Sodium Carboxymethylcellulose, and
• Sodium Salt Cellulose Gum to name a few.
Harmonisation of terms and systems, let alone legislative frameworks, is a monumental task. Even with the EU attempting to simplify things, this substance is still the topic of much debate and potential complexity. 
The discussion around the safety of Carboxymethylcellulose is ambiguous, to say the least. Until there is further research on the topic, and the use of interchangeable terminology is addressed, I believe that it may be too challenging for the wider population to reach an informed, unbiased consensus.
Some chemical preservatives are just outright scary. As you learn more about what is considered acceptable in foods you may find yourself dodging anything that isn’t made at home from scratch. Sometimes that’s just the best way to go. Considering avoiding CMC and CMC-Na as much as possible may be a good idea for now.
- “CFR – Code of Federal Regulations Title 21 – Sec. 182.1745 Sodium carboxymethylcellulose” – FDA Staff, Last Updated 29 November 2022 [US Department of Health & Human Services] [Archive]
- “Application A1047 Sodium Carboxymethylcellulose as a Food Additive in Wine Risk and Technical Assessment Report” – FSA Staff, 4 October 2011 [Food Standards Australia & New Zealand] [Archive]
- “What is the Difference Between Sodium CMC and CMC” – S. Madhu, 1 September 2021 [Difference Between] [Archive]
- “Croscarmellose (synonym: Carboxymethylcellulose)” – PubChem Staff, 24 June 2005 [PubChem] [Archive]
- “Sodium carboxymethyl cellulose” – PubChem Staff, 5 February 2008 [PubChem] [Archive]
- “Is common food additive to blame for rising rates of bowel disease?” – M. Healy, 25 February 2015 [LA Times] [Archive]
- “Food Additives Inflame Mouse Guts By Disturbing Microbes” – E. Yong, 26 February 2016 [National Geographic] [Archive]
- “CAS Database List: 9004-32-4” – Chemical Book Staff, Last Checked 19 January 2023 [Cheemical Book] [Archive]
- “Naturapolyceutics: The Science of Utilizing Natural Polymers for Drug Delivery – Figure 3: A simple process of carboxymethylation of a natural polymer” – N. C. Ngwuluka, N. A. Ochekpe, O. Aruoma, May 2014 [ResearchGate] [Archive]
- “Carboxymethyl Cellulose Produced at Different Mercerization Conditions and Characterized by NIR FT Raman Spectroscopy in Combination with Multivariate Analytical Methods” – H. A. Ambjörnsson, K. Schenzel,U. Germgård, 2013 [NC State University – BioSources] [Archive]
- “Production process of carboxymethyl cellulose” – S. Slotte, May 2021 [University of Oulu] [Archive]
- “Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome” – B. Chassaing, C. Compher, B. Bonhomme, Q. Liu, Y. Tian, W. Walters, L. Nesse, C. Delaroque, F. Hao, V. Gershuni, L. Chau, J. Ni, M. Bewtra, L. Albenberg, A. Bretin, L. McKeever, R. E. Ley, A. D. Patterson, G. D. Wu, A. T. Gewirtz, J. D. Lewis, 10 November 2021 [American Gastroenterological Association] [Archive]
- “The Role of Carboxymethylcellulose in Health and Disease: Is the Plot Thickening?” – J. Wellens, S. Vermeire, J. Sabino, 10 January 2022 [American Gastroenterological Association] [Archive]
- “Impact of Food Additives on Gut Homeostasis” – F. Laudisi, C. Stolfi, G. Monteleone, 1 October 2019 [PubMed] [Archive]
- “Recent Developments of Carboxymethyl Cellulose” – S. Rahman, S. Hasan, A. S. Nitai, S. Nam, A. K. Karmakar, S. Ahsan, M. J. A. Shiddiky, M. B. Ahmed, 20 April 2021 [PubMed] [Archive]
- “Is sodium carboxymethyl cellulose (CMC) really completely innocent? It may be triggering obesity” – A. Baran, E. Sulukan, M. Türkoğlu, A. Ghosigharehagaji, S. Yildirim, M. Kankaynar, I. Bolat, M. Kaya, A. Topal, S. B. Ceyhun, 25 September 2020 [PubMed] [Archive]
- “Toxicity study of food-grade carboxymethyl cellulose synthesized from maize husk in Swiss albino mice” – M. I. H. Mondal, M. S. Yeasmin, 6 August 2016 [PubMed] [Archive]
- “Dietary Emulsifier-Induced Low-Grade Inflammation Promotes Colon Carcinogenesis” – E. Viennois, D. Merlin, A. T. Gewirtz, B. Chassaing, January 2017 [PubMed] [Archive]
- “Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome” – B. Chassaing, O. Koren, J. K. Goodrich, A. C. Poole, S. Srinivasan, R. E. Ley, A. T. Gewirtz, 5 March 2015 [PubMed] [Archive]
- “Dietary emulsifiers directly alter human microbiota composition and gene expression ex vivo potentiating intestinal inflammation” – B. Chassaing, T. V. Wiele, J. D. Bodt, M. Marzorati, A. T. Gewirtz, August 2017 [PubMed] [Archive]
- “Dietary emulsifiers consumption alters anxiety-like and social-related behaviors in mice in a sex-dependent manner” – M. K. Holder, N. V. Peters, J. Whylings, C. T. Fields, A. T. Gewirtz, B. Chassaing, G. J. Vries, 17 January 2019 [PubMed] [Archive]
- “Effects of regulating intestinal microbiota on anxiety symptoms: A systematic review” – B. Yang, J. Wei, P. Ju, J. Chen, 17 May 2019 [PubMed] [Archive]
- “EUR-Lex – 32013R1274 – EN” – Eur-Lex Staff, 6 December 2013 [Eur-Lex] [Archive]
Last Updated on 7 months by D&C Editorial Team