Can artificial sweeteners like aspartame be trusted?

Sweeteners are artificial sugar substitutes, used to avoid the effects of using sugar. They can be used to aid weight loss, and are also found in certain food products and soft drinks. Lea Paterson / Keystone

The sweetener aspartame is a “possible carcinogen” but it remains safe to consume at already-agreed levels, two groups linked to the World Health Organization (WHO) declared on Friday. The artificial sweetener is omnipresent in low-calorie soft drinks, sweets and other processed foods. Two Swiss scientists are testing other alternatives to sugar that may offer more benefits than risks.

Millions of people suffering from diabetes – 500,000 in Switzerland aloneExternal link – or those tired of fighting the ubiquitous temptation of sugar have come to rely on sweeteners as a sugar alternative that won’t boost their blood sugar levels or daily calorie intake. Over the past decade, the food industry has been riding this wave, using sweeteners in an increasing number of products. By 2019, the amount of non-nutritive sweeteners consumed per person had increasedExternal link globally by 36% in beverages and by 3% in packaged foods compared to 2007.

But in May this year, the World Health Organization (WHO) published new guidelinesExternal link advising against the use of sweeteners to control body weight or reduce the risk of noncommunicable diseases (NCDs). In July, new rulingsExternal link from two different WHO-linked groups said aspartame, a popular artificial sweetener found in Diet Coke, chewing gum, yoghurt and other food products, is a “possible carcinogen” but it remains safe to consume at the existing daily intake guidelines. For aspartame, this limit is 40 milligrams of aspartame per kilogram of body weight per day, according to the WHO/FAO Joint Committee on Food Additives (JECFA)  That means an adult weighing 70 kg (approximately 150 pounds) would need to consume between 9 and 14 cans of diet soft drink in one day to surpass the limit. 

Several other studies have suggested that, in the long run, sweeteners can cause the very thing they promise to fight – obesity and chronic diseases, including diabetes. But the reliability of these studies is a source of debate.

Meanwhile, in Switzerland, two scientists are conducting promising clinical studies on two types of sweeteners: erythritol and xylitol.

A sweetness that saves teeth

Bettina Wölnerhanssen, a Swiss-Norwegian doctor, remembers her early childhood years in Sweden. Since the 1950s, the country has had a tradition called Lördagsgodis, or Sweets Saturday.

“It was the day when we girls and boys could eat sweets and candy,” she recalls. Sweets Saturday began as an attempt to limit sugar consumption and thus reduce the incidence of tooth decay, which was very high in Sweden at the time. Then, in the 1970s, xylitol came into play. Finnish scientists had discovered that this sugar alcohol found in some fruits and vegetables actually prevented cavities.

Another sugar alcohol, erythritol, was also already known for its sweetening power, low-calorie content and the fact that it did not adversely affect dental health. But while xylitol had already been produced and used as a sugar substitute for a long time, especially in the Nordic countries, erythritol was only authorised for trade in 1990 in Japan. From then on, more than sixty countries approved it – the European Union did so only in 2006 – and its popularity grew.

Besides having practically zero calories, erythritol has greater intestinal tolerability than xylitol. These characteristics make it easily adaptable to various sweet recipes.

Over time, studies on these sugar alcohols have multiplied, demonstrating positive effectsExternal link on animals, such as anti-diabetic properties and blood glucose reduction in both healthy and diabetic rats. “It was at that point that I thought maybe we could show whether this also happened in humans and what the mechanisms were,” says Wölnerhanssen. This is the goal of her research group at the Claraspital hospital in Basel.

Bettina Wölnerhanssen and Anne Christin Meyer-Gerspach jointly lead research into metabolic diseases at the Claraspital hospital in Basel. Claraspital

Feeling full without calories

In Switzerland, erythritol and xylitol came onto the market in recent years. “Our research group is probably the only one interested in these sweeteners in Switzerland,” says Wölnerhanssen. Together with her colleague Anne Christin Meyer-Gerspach, she gained international recognition for publishing the first research on these two substances in 2016. Besides studying the sugar alcohols’ effects on insulin and blood sugar levels, the scientists’ research focused on the release of satiation hormones, which signal when we should stop eating.

When people consume sugar, their levels of satiation hormones increase; they feel satisfied and rewarded and experience a feeling of “fullness”. This does not happen with most artificial sweeteners, but the two scientists observedExternal link for the first time in a small group of people that the intake of erythritol and xylitol causes the release of satiation hormones. “ In the brain, the reward centre is stimulated, similar to sugar, ” Meyer-Gerspach says.

+ Read more about the political side of the sugar debates in Switzerland

This could help people suffering from obesity – who produce fewer satiation hormones – to reduce their sense of hunger and their weight gain. Unlike sugar, erythritol and xylitol have very few calories.

Wölnerhanssen and Meyer-Gerspach are now conducting two clinical External linktrialsExternal link on adults and adolescents to investigate the effects of erythritol and xylitol on the way the body assimilates sugar. Several External linkstudiesExternal link conducted in recent years have observed that the use of popular artificial sweeteners, especially sucralose and saccharin, is associated with a change in the bacterial flora of the gut. This could lead to higher blood sugar levels and therefore an increased risk of developing diabetes and other diseases.

Alternative sweeteners in the crosshairs

Like other sugar substitutes, erythritol and xylitol have also been scrutinised by some studies. Researchers who examined the cardiac health of over 4,000 patients in the United States and Europe recently found that high blood levels of erythritol were associated with the risk of suffering a heart attack or stroke. The resultsExternal link were published in February.

According to Wölnerhanssen, this study offers some important insights but leaves many open questions. The scientist believes that it is very difficult to prove a direct causal relationship through studies in which the effects of chemicals are simply observed on a group of people. “They can be influenced by too many factors, especially since erythritol is also produced by the human body,” says Wölnerhanssen.

For the same reasons, her colleague Meyer-Gerspach questions the validity of scientific research finding that people who consume a lot of artificial sweeteners are more likely to be overweight and suffer from diabetes. “There are currently no studies that clearly prove that artificial sweeteners are harmful,” she argues.    

More research required on sweetener safety

The debate rages on over the effects of sweeteners. Organisations representing sweetener companies, such as the International Sweeteners Association, claimExternal link the WHO’s May recommendations are not scientifically rigorous, nor based on robust evidence. The Swiss Federal Office of Public Health has not taken a stand against the WHO recommendations but continues to consider sweeteners “safe”.

Magali Rios-Leyvraz, an expert in nutritional epidemiology and the main author of the reviewExternal link that the WHO used as a basis for its assessment on sweeteners, clarified in an e-mail that the document analyses the most current scientific evidence (more than 283 studies) on these substances. “It is the most comprehensive review on this topic to date,” she writes. However, she believes that further research is needed to confirm the results, especially in children and pregnant women.

Sugar alcohols such as xylitol and erythritol were not included in the WHO’s analysis. Rios-Leyvraz says their effects on human health should be investigated further.

Although she advises caution in evaluating research on sweeteners, Wölnerhanssen argues that it would be an illusion to believe that they have no effect on our bodies. “Like all chemicals, they are not inert,” she says. Her solution?

“Drink more water and fewer sweet drinks.”    

Translated from Italian; edited by Sabrina Weiss and Veronica DeVore