A large study involving more than 80,000 women found that drinking two or more diet drinks a day - including fizzy drinks and fruit-based diet drinks - increased the risk of stroke by 23 per cent.

Compared with women who consumed diet drinks less than once a week or not at all, women who consumed two or more artificially-sweetened drinks per day were also 29 per cent more likely to develop heart disease and 16 per cent more likely to die from any cause.

Further analysis showed that some groups of women were most at risk, with those drinking two or more diet drinks a day who were also obese having more than double the stroke risk.

African-American women also had a higher risk of stroke.

Dr Yasmin Mossavar-Rahmani, lead author of the study and associate professor of clinical epidemiology and population health at the Albert Einstein College of Medicine in the Bronx, New York, said: "Many well-meaning people, especially those who are overweight or obese, drink low-calorie sweetened drinks to cut calories in their diet.

"Our research and other observational studies have shown that artificially sweetened beverages may not be harmless and high consumption is associated with a higher risk of stroke and heart disease."

The authors stressed that the study found a link but could not prove that diet drinks cause strokes and heart problems.

The research, published in the journal Stroke, included data from 81,714 post-menopausal women (who were aged 50-to-79 at the start of the study) and who were tracked for an average of 12 years.

One serving of diet drink was regarded as 355ml.

Dr Mossavar-Rahmani said the study had not looked at individual artificial sweeteners, saying: "We don't know specifically what types of artificially sweetened beverages they were consuming, so we don't know which artificial sweeteners may be harmful and which may be harmless."

The American Heart Association has recently published a science advisory which found there was inadequate scientific research to conclude that low-calorie sweetened beverages do or do not affect the risk of heart disease and stroke.

But it states that water is the best choice for a no-calorie drink.

Dr Rachel Johnson, professor of nutrition emeritus at the University of Vermont and chairwoman of the writing group for the American Heart Association's science advisory, Low-Calorie Sweetened Beverages And Cardiometabolic Health, said: "Unfortunately, current research simply does not provide enough evidence to distinguish between the effects of different low-calorie sweeteners on heart and brain health.

"This study adds to the evidence that limiting use of diet beverages is the most prudent thing to do for your health."

Australian Associated Press