People looking to lose weight should skip sugar substitutes, according to new guidance from the World Health Organization.

The United Nations agency said Monday that a systematic review of the available evidence suggests use of non-sugar sweeteners “does not confer any long-term benefit in reducing body fat in adults or children.”

It also shows there may be “potential undesirable effects” from the long-term use of these sweeteners, such as an “increased risk of type 2 diabetes, cardiovascular diseases, and mortality in adults.”

Replacing sugar with non-sugar sweeteners “does not help with weight control in the long term. People need to consider other ways to reduce free sugars intake, such as consuming food with naturally occurring sugars, like fruit, or unsweetened food and beverages,” Francesco Branca, WHO Director for Nutrition and Food Safety, said in a press release. Artificial sweeteners “are not essential dietary factors and have no nutritional value. People should reduce the sweetness of the diet altogether, starting early in life, to improve their health.”

The recommendation applies to all people except individuals with pre-existing diabetes, the review says, as assessing this group was simply beyond the scope of the data used.

What artificial sweeteners are bad for you?

WHO’s recommendation encompasses “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.

The agency notes common varieties include acesulfame K, aspartame, advantame, cyclamates, neotame, saccharin, sucralose, stevia and stevia derivatives.

This guidance comes months after a study found erythritol, a zero-calorie sugar substitute used to sweeten low-cal, low-carb and “keto” products, is linked to higher risk of heart attack, stroke and death.

Researchers at the Cleveland Clinic studied over 4,000 people in the U.S. and Europe and found those with higher blood erythritol levels were at elevated risk of experiencing these major adverse cardiac events. The research, published in the journal Nature Medicine, also found erythritol made blood platelets easier to form a clot.

Sugar-free products containing erythritol have been previously recommended for people with obesity, diabetes or metabolic syndrome as ways to manage sugar and calorie intake. Erythritol is one ingredient in the common calorie-free stevia sweetener Truvia, for example.