An astonishing new discovery suggests that those diet sodas you’re drinking as part of a diet may actually be doing you more harm than good. A new study from the American Heart Association claims that artificially sweetened beverages may be associated with dementia and stroke, and more research will be needed to figure out exactly why that is.

The study, published in the AHA’s journal Stroke, found that artificially sweetened drinks were associated with an increased risk of stroke and dementia. However, scientists cautioned that there was only an association, and since scientists don’t know what would cause this increase, more research will be needed to determine if artificially sweetened drink actually increase the risk of dementia and stroke or if they simply are more commonly consumed by people at a high risk of those diseases.

Scientists didn’t find a similar association with sugary beverages like regular soda and fruit drinks, which are often blamed as a cause in the rising obesity epidemic in America. The study is an eye-opening reminder that there’s a lot we don’t know about how diet drinks affect our bodies.

“Our study shows a need to put more research into this area given how often people drink artificially-sweetened beverages,” said Matthew Pase, Ph.D., a senior fellow in the department of neurology at Boston University School of Medicine, Swinburne University of Technology in Melbourne, Australia, and the Framingham Heart Study.

“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. We recommend that people drink water on a regular basis instead of sugary or artificially sweetened beverages.”