South Yorkshire residents are being warned just one diet drink a day can triple the risk of a deadly stroke.
Researchers also described links to dementia as a “worrying association” by experts.
But the findings were dismissed by some British authorities, while others have called for more investigation.
The US study found those who drank a can of artificially-sweetened pop — such as Diet Coke or Pepsi Max — daily were at three times the risk of suffering the most common form of stroke compared to non-drinkers. They were also 2.9 times more likely to develop Alzheimer’s.
But after accounting for all lifestyle factors, the researchers found the link to dementia was statistically insignificant. However, the impact on stroke risk remained.
The team from Boston University School of Medicine looked at ten years’ worth of data from more than 4,300 people.
The team's Dr Matthew Pase urged people to drink water instead — a stance supported by the National Obesity Forum in the UK.
But Professor Louis Levy, from Public Health England, said: “This study doesn’t show the full picture and more evidence is needed before any definite conclusions can be drawn.”
And Dr James Pickett, of the Alzheimer’s Society, added: “This research does not show that artificially sweetened drinks cause dementia. But it does highlight a worrying association that requires further investigation.”