Having two or more diet drinks a day could raise heart attack and stroke risk in postmenopausal women.

Postmenopausal women who consumed two or more diet drinks per day were about 30 percent more likely to suffer a cardiovascular event and were 50 percent more likely to die from a related disease, an American College of Cardiology news release reported.

"Our findings are in line with and extend data from previous studies showing an association between diet drinks and metabolic syndrome," Ankur Vyas, M.D., fellow, Cardiovascular Diseases, University of Iowa Hospitals and Clinics, and the lead investigator of the study, said in the news release. "We were interested in this research because there was a relative lack of data about diet drinks and cardiovascular outcomes and mortality."

The researchers asked 59,614 women about their diet drink consumption habits in a questionnaire. The women were divided into four groups:  "two or more diet drinks a day, five to seven diet drinks per week, one to four diet drinks per week, and zero to three diet drinks per month," the news release reported.

After an average follow-up of 8.7 years; the team found instances of "coronary heart disease, congestive heart failure, heart attack, coronary revascularization procedure, ischemic stroke, peripheral arterial disease and cardiovascular death" occurred in 8.5 percent of the women who consumed at least two diet drinks per day. These instances occurred in 6.9 percent in the five-to-seven diet drinks per week group; 6.8 percent in the one-to-four drinks per week group; and 7.2 percent in the zero-to-three per month group, the news release reported.

These statistics remained even when the researchers adjusted for other risk factors such as "body mass index, smoking, hormone therapy use, physical activity, energy intake, salt intake, diabetes, hypertension, high cholesterol and sugar-sweetened beverage intake," the news release reported. Women who consumed two or more diet beverages a day were also more likely to have these risk factors.

"We only found an association, so we can't say that diet drinks cause these problems," Vyas said. "It's too soon to tell people to change their behavior based on this study; however, based on these and other findings we have a responsibility to do more research to see what is going on and further define the relationship, if one truly exists. This could have major public health implications."