Sugar substitutes such as stevia, aspartame and sucralose do not help people lose weight in the long run and may instead pose health risks, the World Health Organization has warned.

A systematic review of the available evidence "suggests that use of NSS [non-sugar sweeteners] does not confer any long-term benefit in reducing body fat in adults or children,” the WHO said in a statement.

“Results of the review also suggest that there may be potential undesirable effects from long-term use of NSS, such as an increased risk of type 2 diabetes, cardiovascular diseases, and mortality in adults,” it added.

Francesco Branca, WHO director for nutrition and food safety, said replacing sugars with artificial sweeteners "does not help with weight control in the long term,” and instead, “people need to consider other ways to reduce free sugars intakes, such as consuming food with naturally occurring sugars, like fruit, or unsweetened food and beverages”.

Artificial sweeteners are “not essential dietary factors and have no nutritional value,” Branca emphasised.

“People should reduce the sweetness of the diet altogether, starting early in life, to improve their health”.

Last year, a large study in France flagged a possible link between artificial sweeteners and an increased risk of cancer. And national health organisations such as Canada’s have long warned that zero-calorie or low-calorie sugar substitutes are neither necessary nor helpful.

Aspartame, stevia, sucralose all targeted

“Sugar substitutes do not need to be consumed to reduce the intake of free sugars,” the guidelines say, adding that, because “there are no well-established health benefits associated with the intake of sweeteners, nutritious foods and beverages that are unsweetened should be promoted instead”.

The WHO discourages the consumption of “all synthetic and naturally occurring or modified non-nutritive sweeteners that are not classified as sugars found in manufactured foods and beverages, or sold on their own to be added to foods and beverages by consumers”.

That includes acesulfame K, aspartame, advantame, cyclamates, neotame, saccharin, sucralose, stevia and stevia derivatives.

The recommendations do not apply to personal care and hygiene products containing NSS, such as toothpaste, skin cream, and medications, or to low-calorie sugars and sugar alcohols (polyols). These sugars or sugar derivatives do contain calories - they are therefore not considered sugar substitutes - and are commonly present in various food products such as sugar-free chewing gum and sugar-free candy.

New guidance sparks criticism

WHO’s new guidance applies to all people except those with pre-existing diabetes.

However, WHO emphasised it had been assessed “as conditional” due to the diversity of participants in the studies that formed the basis for its conclusions, as well as the very complex consumption habits of sugar-free sweeteners.

Some nutrition experts have quickly jumped in to point these out, saying the new guidelines were largely based on observational studies that do not establish a direct link between sweeteners and weight control.

First of all, it is important to understand the WHO’s advice “is to governments and policymakers, not to individuals,” said Tom Sanders, a professor emeritus of nutrition and dietetics at King's College London.

However, because of the way they have been presented, people are taking these recommendations as direct advice, he told Euronews Next, adding he expects them to create “a lot of confusion amongst consumers”.

“On one hand, they are being told by government, ‘avoid sugar-sweetened beverages,’ and on the other, ’well, actually you shouldn't be drinking artificial sweeteners’”.

The WHO’s review “does not really show any definite adverse effects, and they do sort of miss out on quite an important one, which is dental caries in children,” Sanders added, noting there is “clear evidence” that replacing sugar sweeteners does help with dental care.

Sanders criticised the guidance for not taking into account “the real-world situation,” particularly in the field of dietetics.

“Sometimes what you're trying to do is get people to control their weight, which is to reduce their calorie intake, and it can help if people are drinking a full sugary drink to switch to a reduced-calorie drink or zero-calorie drink,” he explained.

Indeed, artificial sweeteners have no nutritional value, but a lot of other things in our diet, like tea or coffee, also don’t, he said, “but, you know, people drink them rather than just drink water because they like the taste of it”.