An edible additive used in foods such as baked goods, ice cream and salad dressings has the potential to harm our gut microbiota, finds a study.

Introduced into the modern diet nearly half a century ago, the food additive E415, also known as xanthan gum, is also widely used as a substitute for gluten in gluten-free foods.

When it was first introduced, xanthan gum was thought to not affect us as it was not digested by the human body.

However, the new study, published in the journal Nature Microbiology shows that the additive nevertheless affects the bacteria that live in our intestines. And these bacteria are important for our health and well-being.

“So far xanthan gum is considered a keto-friendly product. This is because it is believed that xanthan is not digested by the body and therefore it doesn’t count in the daily calorie or macronutrient intake,” said researcher Sabina Leanti La Rosa from Norwegian University of Life Sciences (NMBU) in Norway.

However, she explains, the new study shows that gut bacteria break down xanthan gum to its constituent monosaccharides, which are subsequently fermented to produce short-chain fatty acids that can be assimilated by the human body. Short-chain fatty acids are known to supply up to 10 per cent of calories to humans.

This suggests xanthan gum, approved as safe to use in foodstuffs in large parts of the world based on assessments made 50 years ago, could in fact add to a person’s calorie intake.

When xanthan gum was first introduced, it was thought that the additive went straight through the body without affecting the person who ate it.

But now the researchers noted that we are starting to see long-term effects of xanthan gum that were not seen earlier.

“We only see these changes in gut bacteria of people eating a ‘westernised diet’ where processed foods and additives make up a significant part of the food intake. For example, we do not see the same changes in indigenous people from different parts of the globe who eat limited amounts of processed foods,” La Rosa explained.

“Based on this study, we cannot conclude if and how xanthan gum affects our health. But we can say that the additive affects the microbiota in the gut of people who consume it through food,” she added.

The researchers called for more research to understand the impact of xanthan gum on the human gut.