A popular zero-calorie sweetener popular in keto diets has been linked to strokes, heart attacks, blood clots and death, according to a new study.

The study, published in the journal Nature Medicine, found that erythritol appeared to be causing blood platelets to clot more readily, CNN reported. Those clots can then break off and travel to the heart, triggering a heart attack, or the brain, elevating stroke risks.

“The degree of risk was not modest,” said lead study author Dr. Stanley Hazen, director of the Center for Cardiovascular Diagnostics and Prevention at the Cleveland Clinic Lerner Research Institute. “If your blood level of erythritol was in the top 25% compared to the bottom 25%, there was about a two-fold higher risk for heart attack and stroke. It’s on par with the strongest of cardiac risk factors, like diabetes.”

Erythritol is a sugar alcohol that when artificially manufactured has no lingering aftertaste, doesn’t impact blood sugar and has less of a laxative effect than some other sugar alcohols, CNN said. It is the largest ingredient by weight in many “natural” stevia and monkfruit products that are popular with low-carb dieters.

You can read more on CNN here.