Drinking diet drinks every day almost triples your risk of having a stroke or getting dementia, scientists have shown.
According to the research, sugary or regular drinks did not carry the same health risk – but people who consumed at least one artificially sweetened drink a day were nearly three times more likely to suffer a stroke or dementia.
But scientists warned people should not view sugary drinks as a “healthy option” and instead urged people to drink water, low-fat milk or other drinks without sweetener.
The diet drinks industry is booming with low and no calorie drinks making up 45 per cent of all fizzy drinks sold in 2015, according to the British Soft Drinks Association.
The new research, published in the American Heart Association's journal Stroke, is based on food questionnaires for more than 4,300 people taking part in the Framingham Heart Study.
Those in the stroke arm of the study were over the age of 45, while those in the dementia arm were over 60.
All participants filled in questionnaires on their food and drink intake at three separate points during the 1990s.
Researchers then followed the group for 10 years, noting 97 cases of stroke during that period, and 81 cases of dementia (63 cases were specifically Alzheimer's disease).
After adjusting for factors that could influence the results, such as age, sex, education, calorie intake, exercise and smoking, people who had at least one diet drink a day had an almost three times increased risk of dementia or stroke.
The researchers said future studies should look at the effect of diet drinks on factors known to increase the risk of stroke and dementia, such as high blood pressure.
Matthew Pase, senior fellow in the department of neurology at Boston University School of Medicine, said: "Our study shows a need to put more research into this area given how often people drink artificially sweetened beverages.
"Although we did not find an association between stroke or dementia and the consumption of sugary drinks, this certainly does not mean they are a healthy option.”
In October last year researchers in Sweden found two glasses of Diet Coke a day doubles the risk of diabetes.
Additional reporting by Press Association.