People who regularly have two or more diet soft drinks a day could be up to 50 per cent more likely to die from heart disease, a new study has shown.

Artificially sweetened fizzy drinks, though marketed as a viable healthy alternative, were linked to a host of health problems including strokes and heart attacks.

Compared to those who never or rarely consume the drinks, regular users were 30 per cent more likely to suffer what was described as a "cardiovascular event".

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Experts analysed the diet drink intake of almost 60,000 participants in the women's health iInitiative, a long-running US study looking at cardiovascular health among middle-aged women.

And while their statistics were taken from an impressively large sample size, the scientists stressed that they could only prove an "association" between health problems and diet drink intake - not a direct causal link.

"Our findings are in line with and extend data from previous studies showing an association between diet drinks and metabolic syndrome," said Dr Ankur Vyas, of the University of Iowa Hospitals and Clinics, lead investigator of the study. The syndrome is associated with a cluster of risk factors for heart disease, including high blood pressure, high cholesterol and weight gain.

The results of the study were presented at the annual scientific sessions of the American College of Cardiology, in Washington.

The average age of women in the diet drink study was 62.8, and they had to have had no history of cardiovascular disease to be included in the analysis.

Through a questionnaire, the women were asked to report their diet-drink consumption over the previous three months. A drink was defined as a 12oz (355ml) beverage and included diet soft and fruit drinks.

After an average follow-up period of around nine years, a combination of negative outcomes including coronary heart disease, congestive heart failure, heart attack, ischemic stroke, peripheral arterial disease and cardiovascular death were seen in some 8.5 per cent of women who consumed two or more diet drinks a day.

That compared with 6.9 per cent of women who had five to seven drinks per week, 6.8 percent having one to four drinks per week, and 7.2 percent in those having zero to three diet drinks per month.

"We only found an association, so we can't say that diet drinks cause these problems," Dr Vyas said, adding that other factors may explain the apparent connection between diet drink consumption and risk of heart attack and stroke.

For instance, he noted that women who consumed two or more diet drinks per day were younger, more prone to be smokers, and had a higher prevalence of diabetes, high blood pressure and of being overweight.

Dr Vyas said more studies are needed to more closely assess the risk of diet sodas and cardiovascular risks, if such a connection actually exists.

Previous studies have suggested a connection between artificially sweetened drinks and weight gain in adults and teens, and a likely increase in metabolic syndrome.

Additional reporting by Reuters