In May 2023 the WHO published a guideline on non-sugar sweeteners, and the coverage collapsed it into “sweeteners are bad for you”. That is not what the document says, and the gap between the two is worth understanding because it changes what you would do about it.
The recommendation, in full
WHO suggests that non-sugar sweeteners not be used as a means of achieving weight control or reducing the risk of noncommunicable diseases. It is a conditional recommendation.
Conditional, in WHO language, is a technical term: the guideline development group was less certain that the benefits of following the advice outweigh the downsides, or judged the net benefit small. WHO itself says conditional recommendations require substantive discussion among policymakers before being adopted as policy. That is a long way from a warning label.
What it is based on
Two findings. First, the reviewed evidence suggests non-sugar sweeteners confer no long-term benefit in reducing body fat in adults or children. Second, there were signals of possible undesirable effects with long-term use — associations with type 2 diabetes, cardiovascular disease and mortality in adults.
The second of those is observational, and the WHO says so. Association studies of sweetener use have a well-known problem: the people who drink diet soft drinks are disproportionately people already managing weight or diabetes, which is precisely the kind of reverse causation that no amount of statistical adjustment reliably removes.
What it is not
It is not a safety assessment. Sweetener safety in the EU is EFSA’s job, handled through the additives approval process with an acceptable daily intake for each substance, and this guideline does not revisit or contradict any of it. WHO said as much explicitly.
It also does not apply to sugars naturally present in food, to sugar alcohols (polyols), or to people with pre-existing diabetes, who were excluded from the scope.
The claim is: sweeteners do not appear to be a useful long-term tool for losing weight. Not: sweeteners are dangerous.
How this fits with the sugar guideline
The two documents point in the same direction. WHO’s 2015 sugars guideline recommends reducing free sugars to under 10% of total energy, with a conditional further recommendation of under 5%. The 2023 sweetener guideline adds that swapping the sugar for a sweetener is not the way to get there — the intended route is fewer sweet foods and drinks overall, not a substitution that leaves the taste for sweetness in place.
That is the actual argument, and it is a behavioural one rather than a toxicological one.
What a sensible reader does with this
If you drink four sugary soft drinks a day and switching them to diet versions cuts a substantial amount of sugar out of your week, that switch has not been declared harmful and the sugar reduction is real. The guideline’s point is that the switch alone is unlikely to be the thing that changes your weight a year from now.
If you are choosing between sweetened and unsweetened as a habit — coffee, tea, yoghurt, water — the guideline is quietly recommending the unsweetened option, on the grounds that it is the only one with an evidence base for the outcome people are after.
Neither of those is a reason to panic about the sweetener in the drink you had yesterday.
