May 28 (UPI) -- E-cigarettes are largely considered safer than traditional cigarettes, but a new study suggests use of the devices -- as well as the flavors, regardless of nicotine content -- may pose a new risk for heart disease.
When researchers exposed the e-cigarette flavorings to lab-grown endothelial cells, which line the interior of blood vessels, it increased levels of molecules that bring on DNA injury and cell destruction, according to research published Monday in the Journal of the American College of Cardiology.
These endothelial cells support heart and cardiovascular health, but when damaged, can lead to an inability to heal wounds and form new vascular tubes. This damage can ultimately lead to cardiovascular disease.
"Until now, we had no data about how these e-liquids affect human endothelial cells," Joseph Wu, director of the Stanford Cardiovascular Institute and study senior author, said in a news release. "This study clearly shows that e-cigarettes are not a safe alternative to traditional cigarettes. When we exposed the cells to six different flavors of e-liquid with varying levels of nicotine, we saw significant damage. The cells were less viable in culture, and they began to exhibit multiple symptoms of dysfunction."
For the study, researchers looked at the effects caramel, cinnamon, fruit, menthol, sweet tobacco, sweet butterscotch and vanilla e-cigarette flavors on endothelial cells derived from human induced pluripotent stem cells.
For each flavor, human iPS cells were exposed to nicotine levels of 0, 6 and 18 milligrams per milliliter. Among the flavors, the cinnamon and menthol seemed to pose the biggest threat to the viability of the endothelial cells, the researchers report.
The researchers also exposed blood from e-cigarette users not long after they have vaped for 10 minutes, finding they had roughly the same amount of blood level nicotine as someone who smoked a cigarette for the same amount of time.
Many people use e-cigarettes believing they provide a safer alternative to smoking traditional tobacco cigarettes, but some of the same dangers may still apply.
"When you're smoking a traditional cigarette, you have a sense of how many cigarettes you're smoking," Wu said. "But e-cigarettes can be deceptive. It's much easier to expose yourself to a much higher level of nicotine over a shorter time period."
This research is consistent with other studies that show e-cigarettes can elevate the risk for heart attacks, strokes and depression.
Along with long-term health damage, e-cigarettes have also been linked to more immediate risks. In the last decade, the Food and Drug Administration has received reports of 35 seizures linked to vaping.
"Now we know that e-cigarettes are likely to have other significantly toxic effects on vascular function as well," Wu said. "It's important for e-cigarette users to realize that these chemicals are circulating within their bodies and affecting their vascular health."