Artificial sweeteners can potentially turn healthy bacteria in the gut microbiome into harmful microbes and potentially cause serious health issues such as blood poisoning, scientists have said.


UK researchers have found that sugar substitutes such as saccharin, sucralose, and aspartame – found in soft drinks and processed foods – can cause beneficial bacteria in the intestines such as E. coli (Escherichia coli) and E. faecalis (Enterococcus faecalis) to become pathogenic, or disease causing.

Bacteria like E. faecalis are able to cross the gut wall and enter the blood stream, which can lead to a life-threatening condition caused by blood poisoning (septicaemia) known as sepsis. These disease-causing microbes can also accumulate in the liver, lymph nodes and spleen, and cause a number of other infections.

The researchers said that based on their findings, published in the International Journal of Molecular Sciences, it is important to understand more about the impact of sweeteners on health.

“Our study is the first to show that some of the sweeteners most commonly found in food and drink – saccharin, sucralose and aspartame – can make normal and ‘healthy’ gut bacteria become pathogenic," said Dr Havovi Chichger, a senior lecturer in biomedical science at Anglia Ruskin University (ARU).

“These pathogenic changes include greater formation of biofilms and increased adhesion and invasion of bacteria into human gut cells. These changes could lead to our own gut bacteria invading and causing damage to our intestine, which can be linked to infection, sepsis and multiple-organ failure.

“We know that overconsumption of sugar is a major factor in the development of conditions such as obesity and diabetes. Therefore, it is important that we increase our knowledge of sweeteners versus sugars in the diet to better understand the impact on our health.”

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Pathogenic bacteria can invade and kill Caco-2 cells – cells which line the wall of the intestine. The researchers found that an amount of sweeteners equivalent to two cans of diet soft drink can significantly increase the ability of E. coli and E. faecalis to attach to Caco-2 cells.

They also found sweeteners to have an effect on the formation of biofilms – clusters of bacteria that are more likely to secrete toxins and less sensitive to antimicrobial resistance treatment, potentially increasing the risk of disease.


The researchers wrote in their paper: “Since AS (artificial sweeteners) consumption in the diet continues to increase, understanding how this food additive affects gut microbiota and how these damaging effects can be ameliorated is vital.”

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Reader Q&A: Can artificial sweeteners cause weight gain?

Asked by: Ciaran Scanlon, Kildare, Ireland

The evidence on this is conflicting. Long-term studies with large sample sizes have found a correlation between artificial sweeteners and weight gain, but these tend to rely on diet questionnaires, which aren’t accurate. They also can’t say whether, for example, diet soda makes you fat, or overweight people are more likely to drink diet soda.

A 2016 report by health charity Cochrane evaluated the results of lots of more rigorous short-term trials, and concluded that artificial sweeteners actually help with weight loss by replacing sugar calories with non-calorie alternatives.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.