More cancer turned up among heavy sweetener users; cause unproven
In 103,000 French adults, sweetener intake tracked with 13% more cancer and aspartame with 15%. A review of animal and mechanistic work found no route by which it could.
What the study found
Sweetener intake tracked with 13% more cancer in 103,000 adults
Aspartame alone tracked at 15%, and breast cancer at 22%, in the French cohort behind that figure. A rodent re-analysis reported malignancies at doses below the human daily-intake limit. A review of animal and mechanistic work found no route by which they could cause cancer at all.
The caveat · The absolute risk gap is small
The cohort recorded what people chose to consume rather than assigning it, and its own authors flag selection effects, unmeasured differences between users and non-users, and the possibility that illness came first. The percentage rises are real, but the absolute difference in risk between users and non-users is small. The rodent work is the original researchers re-examining their own contested findings, not an independent repeat. The review pointing the other way came from a consultancy regularly retained by regulated industries.
What we don't know
None of the three studies on sweeteners and cancer could settle it: a cohort of people's own choices, a team re-analysing its own rodent work, an industry consultancy's review. The study that could has not been run.