Known food additives affect our gut bacteria

Norwegian University of Life Sciences NMBU

By Tonje Lindrup Robertsen

A wooden spoon and bowl of flour on the table.

Xanthan gum is used as an additive in processed foods and is widely used as a substitute for gluten in gluten-free foods. Photo: Adobe stock

An additive used in processed food leads to changes in our intestinal bacteria, shows new research from NMBU published in Nature Microbiology. The new knowledge should be taken into account when the authorities assess the additives we use in food, say researchers.

Have you heard of E415? Also known as Xanthan gum or xanthan gum. Most likely, you eat this substance quite often. Xanthan gum is used in everyday foods such as baked goods, ice cream and dressings. The substance is also widely used as a substitute for gluten in gluten-free foods and is often recommended for use in low-carb diets.

New research now shows that xanthan gum affects the bacterial flora in our intestines.

The study was recently published in the renowned journal Nature Microbiology and was carried out by a research team from NMBU, in collaboration with the University of Michigan and several other international partners.

We are surprised by how much the human intestinal bacteria have adapted to this additive after it was introduced into the modern diet approximately fifty years ago, says NMBU researcher Sabina Leanti La Rosa.

In the past, it was believed that xanthan gum in food does not affect us because it is not absorbed by the body in digestion. However, the new study shows that the substance still affects the bacteria that live in our intestines.  

The researchers also see that, although it was previously thought that xanthan gum was not digested in the body, the intestinal bacteria have evolved to be able to break down this additive. The smaller molecules are fermented into short-chain fatty acids in the intestine. These fatty acids are then absorbed by the body and used as energy. 

The intestinal bacteria we have examined have a genetic change that shows a very rapid adaptation to this particular additive. Fifty years is not much in this context, says Professor Phil Pope.

He is head of the research group Microbial Ecology and Meta-Omics at NMBU, where the researchers who wrote the study on xanthan gum work.

A completely new food chain in the intestine

The study shows that the gut bacteria of many people living in industrialized countries have developed their own ability to digest xanthan gum. This ability appears to be particularly prominent in a specific intestinal bacterium in the bacterial family Ruminococcaceae .

Using several different methods that analyze genes, proteins and enzymes produced by the intestinal bacteria, the researchers have been able to uncover how this bacterium breaks down xanthan gum. The work includes laboratory testing of samples from humans, mouse experiments and data from large, international databases of the microbes’ genes.

The bacterium that can digest xanthan gum was found in the intestinal flora of a surprising number of people in industrialized countries, says La Rosa.

In some, another type of microbe was also found that used the xanthan gum, this one from the species Bacteroides intestinalis. This microbe somehow managed to “hijack” tiny pieces of the xanthan gum that was produced by the first type of bacteria during the breakdown of the larger xanthan molecules. The Bacteroides bacterium was equipped with its own, very special enzymes that allowed it to eat these small fragments of xanthan gum.

The study thus shows that in many people’s intestinal flora there is now a separate food chain that is run by xanthan gum and that involves at least two different microbes from two different bacterial families.

This gives us an initial framework to better understand how extensive use of new additives in the food we eat affects the microbiota in our intestines, says La Rosa.

The interdisciplinary approach we have used gives us a template for how we can work further to understand how different additives are utilized in the human intestinal flora. The method can also be used to investigate all types of complex ecosystems in the stomach, she says.

The methods we have used definitely push the boundaries of how we can analyze microbes in the future to help us answer important biological questions that are of great importance to society, says Phil Pope. He points out that over time NMBU has built extensive and solid expertise in research into microbes and microbial communities.

The methods we have used push the boundaries of how
we can analyze microbes in the future, says NMBU
researcher Phil Pope.

Starting to see long-term effects

In Norway, around 300 additives are approved for use in food. Xanthan gum, or E415, is one of these. The additive is a fermentation product that is produced by fermenting sugar with the help of the bacterium Xanthomonas campestris. This process creates a jelly-like liquid which is then dried and turned into powder.

  • According to the Norwegian Food Safety Authority, xanthan gum is used as a thickener or stabilizer and is currently permitted to be used in many foodstuffs. Examples of this are ice cream, sweets, baked goods, chocolate milk, ready-made sauces and dressings. Xanthan gum is also used as a substitute for gluten in gluten-free foods and is sold as a separate dietary supplement for low-carb diets.

The additive was developed in California in the sixties and was approved as safe for use in food by the American Food Safety Authority in 1968. It is used today in large parts of the world.

When xanthan gum was first introduced, it was thought that it went straight through the body without being absorbed by the digestive system of the person who ate it. 

– We are now beginning to see long-term effects of the additive that were not seen at the beginning when it was first introduced, says La Rosa.

Xanthan gum is a different type of carbohydrate than what the human body is used to getting through starch from plant foods. It simply has a different chemical structure. Xanthan gum is a type of complex carbohydrate that does not resemble any of the plant fibers we normally eat.

Gluten-free and low-carb

Xanthan gum is often recommended for use in keto and other low-carb diets.

– This is precisely because it has been considered that the substance is not digested by the body and thus should not be counted as part of the calorie intake, says La Rosa.

However, she explains that they now see that the intestinal bacteria break down xanthan gum into smaller molecules. These are fermented in the intestine and then produce so-called short-chain fatty acids. These are absorbed into the body as nutrients.

– The new information therefore indicates that xanthan gum should actually count as part of the calorie intake, she says.

What does it mean for our health?

– Based on this study, we cannot conclude exactly how the changes in the intestinal bacteria affect our health. But we can say that the additive affects the microbiota in the gut of people who ingest it through food, says La Rosa.  

Xanthan gum is therefore approved as safe to use in food in large parts of the world based on research carried out fifty years ago.

A large part of the population in industrialized countries today has a low, but continuous, intake of xanthan gum. Different, smaller groups, such as those with gluten intolerance, can have a much higher intake, and the NMBU researchers therefore believe that the study shows how important it is to have more knowledge about how additives in food affect the intestinal flora and our health.

– We only see the proven change in the intestinal bacteria in people who live in so-called industrialized countries where processed foods and additives make up a significant part of the diet. For example, we do not see the same change in indigenous peoples in different parts of the world, says La Rosa.

La Rosa therefore believes that the authorities should include the new knowledge in the assessments of the additives used in our everyday food.

– This knowledge should change how we look at food additives in general. When xanthan gum came out in the sixties, we didn’t think it had any effect on our health because we had less knowledge than today about how important the gut flora is for health and nutrient absorption. But with increasingly advanced research on microbes, we are now seeing effects that we did not see at the beginning. The authorities should take the new knowledge into account in assessments of additives and we should do even more to understand the effects additives have on our microbiota.


Read the research article in Nature Microbiology:  Mechanistic insights into consumption of the food additive xanthan gum by the human gut microbiota


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Sabina Leanti La Rosa

Associate Professor

Tel . 67232985

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Philip Pope


Tel . 67232540

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Live Heldal Hagen


Tel . 67232481

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Collaboration partners:

University of Michigan, USA (postdoc Matthew Ostrowski and professor Eric C. Martens)

DOE Joint Genome Institute, Berkeley, USA

Purdue University, USA

University of British Columbia, Canada

Center National de la Recherche Scientifique, France


The Research Council

Published 5 April 2022 at 02:33- Updated 23 June 2023 at 06:58