New US research has found that popular chemicals used to flavor e-cigarette liquids may cause changes or damage to heart muscle cells.
Led by Matthew A. Nystoriak, Ph.D from the University of Louisville, the preliminary lab-based research examined 15 chemicals used to flavor e-cigarette liquids, such as such as cinnamon, clove, citrus and floral, both heated and unheated.
E-cigarettes work by heating liquids containing nicotine to turn it into vapor, which users then inhale, or vape.
Many of the liquids are flavored.
Unheated particles of these flavor chemicals can make their way into the heart, with the team finding that the chemicals could cause a wide variety of reactions in the heart cells.
For example, the chemical used for cinnamon flavoring stopped heart cells from moving or contracting even 24 hours later, while chemicals used for clove, floral and citrus flavoring made cells beat faster.
"These effects [from the chemicals] are kind of striking because it suggests that if this compound was interacting with the heart muscle itself, it could do something directly to change how that cell actually functions," said Nystoriak, whose research was released this week at the American Heart Association's Scientific Sessions meeting.
Nystoriak added that the chemicals that did the most significant damage to the cells that keep the heart pumping had an effect before they were heated.
However, there are still many questions about how exactly how the chemicals can affect the heart both when heated and when not.
In addition, as the experiments were done in a petri dish and not on a real heart, the study also doesn't take into account the many variables that are involved in real-life consumption of the chemicals.
However, health experts have long been concerned about the potential dangers of e-cigarettes, partly because little is known about the health risks from flavorings.
Though not involved in this study, Matthew L. Springer, Ph.D., a professor of medicine at the University of California, San Francisco, and an expert on how smoke and aerosol tobacco affect vascular function, commented that chemicals that are "generally recognized as safe" are not necessarily safe for inhalation, adding that cayenne pepper powder is quite safe for eating, but I would not want to inhale it."
"They should not assume that e-cigarettes are harmless just because they don't produce smoke," he continued. "The best thing that you can inhale is clean air."
According to the Centers for Disease Control and Prevention, e-cigarettes might be less harmful than conventional cigarettes but still aren't safe because data shows they can contain harmful substances such as nicotine and lead.