New Research Summary - Trial looking at the effects of a dietary emulsifier on gut health
What is carboxymethylcellulose?
Carboxymethylcellulose (CMC) is a synthetic thickening agent and emulsifier that is made by reacting cellulose (wood pulp, cotton lint) with a derivative of acetic acid (the acid in vinegar).
Also listed as ‘cellulose gum’ on labels, CMC was first approved for use in food products in the 1960s. It was considered safe for consumption, as it is excreted from the body with minimal absorption in the gut. However, even though it may not be absorbed, it does come into contact with the gut microbiota and in 2015 a study by the National Institute of Health found that both CMC and another emulsifier (polysorbate 80) caused changes to the gut environment that increased the risk of inflammatory bowel disease in animals.
Where is carboxymethylcellulose found?
Used to stabilise emulsions and modify the texture of food and drink products, CMC is commonly found in beverages such as protein drinks, milk replacements, sparkling wine and beer. It is also used in bakery products, sauces and condiments, as well as low fat and gluten free products.
Has carboxymethylcellulose been linked to IBD?
When CMC was approved for use back in the 60's, very little was known about our microbiome. Recently, emulsifiers have been linked with inflammation in the gut through interactions with the microbiome and the protective mucus layer. However, most of these studies have been conducted in animal models. There has been one very small human trial which showed a possible link between a different emulsifier carrageenan and ulcerative colitis flare-ups but this trial had multiple limitations and we need much more information in this area to draw firm conclusions.
How did they carry out this study on CMC?
The researchers looked at the impact of CMC on the gut microbiome in people with no known health issues. There was a total of 16 participants who took part in the study and they all lived at the research facility for 11 days, where they consumed identical emulsifier-free diets.
The participants were split into two groups with half the participants (7 people) consuming 15g of CMC per day incorporated into brownies and ice cream. The other half (9 people) were the control group who consumed the brownies and ice cream without the addition of CMC. The trial groups were randomised and blinded, which means that neither the participants or researchers knew who was in which group to eliminate as much bias as possible. Samples of blood, stool and biopsies of gut tissue were collected before and after the trial to look for changes to the microbiome profile, chemicals produced by the microbiota and inflammatory markers.
What did they find?
The trial group who consumed the 15g of carboxymethylcellulose/day experienced significantly more stomach pain and digestive discomfort than the control group.
At the end of the intervention analysis of the participants gut microbiome showed the trial group had less diversity of different bacteria species including lower levels of Faecalibacterium Prausnitzii, which has been linked to IBD. There were also significant changes to the metabolome, which is the range of chemicals produced by the bacteria present during their digestion. The trial group were found to have lower levels of short chain fatty acids and essential amino acids. Short chain fatty acids are thought to be beneficial to us in many ways including gut health and low levels have been associated with multiple diseases including IBD. These changes were evident as early as 3 days after starting to consume CMC and remained throughout the period of CMC consumption. However, they were resolved when subjects were resampled approximately 1 month later after returning to their normal diets.
Finally, 28% of the trial group (2 people) showed evidence that their microbiota was starting to encroach on the protective mucus layer coating the gut. The mucus layer prevents bacteria from coming into contact with the gut lining and an erosion of this mucus layer is another hallmark of IBD. The reason this is concerning is because an interaction between bacteria and the gut lining has the potential to cause an inflammatory response from the immune system.
However, the blood work including inflammatory markers of the participants showed no change throughout the trial period.
What does this mean?
Although we do not currently know what an ideal gut microbiome looks like, we can see from this study that a reduction in faecalibacterium prausnitzii bacteria had a biological impact (a reduction of short chain fatty acids). In some people it also caused a reduction in the protective mucus layer of the gut which has the potential to cause an inflammatory response. Although there was no evidence of an increase in inflammation for any of the participants at the end of the 11 days, we need to consider that this was a very short trial and more research would need to be done to investigate the longer-term impact.
It would appear that the consumption of carboxymethylcellulose at a dose of 15g for 11 days alters the microbiome of healthy people in a way that is considered to be negative for health. However, before we can draw firm conclusions, we need much more research on the subject and in IBD in particular.
It is worth noting that 15g of carboxymethylcellulose is much higher than the quantity likely to be consumed in one day if you follow a balanced diet. The impact of a smaller consumption of CMC daily is not known. However, the researchers considered that 15g of CMC may be representative for someone consuming a highly processed diet, if CMC represented the total amount of different emulsifiers consumed over the course of a day. However, not all emulsifiers have been shown to have similar effects on the microbiome.
How valid is this study?
This study is interesting because the design of the study is considered to be the ‘gold standard’ method for investigating the impact of diet on human participants. In dietary research it is always very difficult to eliminate many confounding factors which may impact the results of the study. As the participants lived at the facility and only ate the food provided to them, this eliminates a lot of factors which usually make diet studies difficult to establish causation.
The design of the study was also high quality using a randomised method to split the participants into the two groups and blinding of the participants and researchers meant that neither were aware which group they were in.
However, the sample size of the group was very small and therefore we have to take into account that any results may be skewed to the participants involved and not be representative of a wider cross section of people. The trial would need to be repeated, on a larger group, in order to see if a similar pattern on the results is found.
Takeaways
For our overall health, whether we have IBD or not, a balanced diet which includes limited ultra-processed foods is advisable. This eating pattern contains minimal additives and emulsifiers and helps to provide adequate nutrition. This may not be possible for some people though for a number of different reasons including socio-economic status, skills, time and knowledge.
However, here are a couple of simple and cost neutral ideas which may help you to remove some emulsifiers or ultra-processed foods from your diet:-
Read the ingredient label – very similar products can contain very different additives. For example, some oat milks contain minimal ingredients oats and rapeseed oil, whilst other brands contain multiple ingredients like emulsifiers such as CMC and carrageenan.
Use butter in moderation instead of margarine which often contains emulsifiers. Where possible use healthy oils such as olive oil.
Gluten or dairy free products - these products can often be mistaken as healthier alternatives to gluten and dairy containing foods but they often contain multiple additives and emulsifiers. Try to choose naturally gluten or dairy free foods and meals where you can if you have to follow a gluten or dairy free diet.
When consuming bakery products such as bread and cakes, opt for fresh versions or home-made options as opposed to those that are mass produced with long shelf lives.
If you would like help and support with your IBD and what dietary and lifestyle changes would be appropriate for you, please get in touch. You can book a free call, where I can get to know you, your journey, your struggles, your life, and we can chat about the best route forward for you. You can also ask any questions you have about working with me.
I have also written a free e-book to help you find a way forward for your everyday life with Inflammatory Bowel Disease. Whether you are right at the beginning of your journey with IBD or have been living with your condition for years and feel like you have tried almost everything, there are things you can do everyday, beyond the medication you are taking, to help you take back control.
Reference
Chassaing B, Compher C, Bonhomme B, Liu Q, Tian Y, Walters W, Nessel L, Delaroque C, Hao F, Gershuni V, Chau L, Ni J, Bewtra M, Albenberg L, Bretin A, McKeever L, Ley RE, Patterson AD, Wu GD, Gewirtz AT, Lewis JD. Randomized Controlled-Feeding Study of Dietary Emulsifier Carboxymethylcellulose Reveals Detrimental Impacts on the Gut Microbiota and Metabolome. Gastroenterology. 2021 Nov 11:S0016-5085(21)03728-8. doi: 10.1053/j.gastro.2021.11.006. Epub ahead of print. PMID: 34774538.
This article was written by Helen Morris (MSc, ANutr) who is our wonderful intern at The NALM Clinic. She's passionate about IBD nutrition research and sharing evidence based IBD nutrition information having lived with Crohn's Disease since 2018.
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