Dr Joseph Wu, who led the study from Stanford Cardiovascular Institute, explains "This study clearly shows that e-cigarettes are not a safe alternative to traditional cigarettes". "But we found the e-liquids caused changes in the endothelial cells that are closely related to those seen during the development of cardiovascular disease".
The researchers investigated the effect of six different popular e-liquid flavors - fruit, tobacco, sweet tobacco with caramel and vanilla, sweet butterscotch, cinnamon, and menthol - with nicotine levels of 0, 6, and 18 milligrams per milliliter on endothelial cells derived from human iPS cells. "What we are finding is that both of them have increased risk", said NYU Langone Health's Outpatient Cardiology Director, Dr. Lawrence Phillips.
Study co-lead Dr Won Hee Lee, who is an assistant professor at the University of Arizona, said: "When you're smoking a traditional cigarette, you have a sense of how many cigarettes you're smoking".
In the study, which Wu's team conducted, six e-liquids with varying concentrations of nicotine were used and the results showed evidence of poor cell survival and increased inflammation on a type of cardiovascular cell.
The American Heart Association found that e-cigarettes can corrupt the lining of the blood vessels, preventing them from dilating and inhibiting the flow of blood.
As proxy for what might happen in someone's blood vessels, the researchers observed how these cells responded when in contact with e-liquids as well as fluid from the blood of a small group of participants who had vaped. Despite the rapid increase in popularity, the cardiovascular effects of chemical flavoring in e-cigarettes largely has been unexplored. After exposing these stem cells to the compounds in e-cigarettes or serum from an e-cigarette, users developed endothelial cell dysfunction associated with decreased viability, accumulation of reactive oxygen species and impaired proangiogenic properties, which is the process of creating new blood vessels.
There is also limited research on e-cigs' effectiveness in helping users quit conventional cigarettes.
The truth is that there is no scientifically accepted evidence that e-cigarettes are 95% safer.
Critics of e-cigarettes say that while the products were initially billed as a somewhat safer way to smoke than traditional cigarettes - a claim that's come into question - many manufacturers have marketed the e-products aggressively to youthful users.
"Most of the discussion about e-cigarettes has focused on the relative harm as compared to traditional cigarettes, the efficacy of e-cigarettes as a cessation device, and the alarming increase of their use in children".
"And now we know that e-cigarettes are likely to have other significantly toxic effects on vascular function as well".
Researchers believe that cinnamon and menthol vape flavorings are more toxic to the body because of the chemicals used to make those flavorings. "Some of the effects of exposure to the e-liquids were dependent on the nicotine concentration but others were independent showing a combined effect of nicotine concentrations and flavoring components". But she said the work should spark additional safety testing.