Some flavorings in e-cigarette liquids could harm the heart, say researchers.
Lead researcher Matthew A. Nystoriak, Ph.D., of the University of Louisville in Kentucky, and colleagues recently presented their findings at the American Heart Association's (AHA) Scientific Sessions 2017, held in Anaheim, CA.
The abstract from the presentation has also been published in the journal Circulation.
Since their introduction to the American market around a decade ago, e-cigarettes have soared in popularity — particularly among youths. According to a 2016 report from the Surgeon General, e-cigarette use among high school students in the United States increased by a whopping 900 percent between 2011 and 2015.
The battery-operated devices are often marketed as a safer alternative to conventional cigarettes, and some research suggests that this is the case. However, scientists are increasingly uncovering the potential dangers of vaping.
Recent studies reported by Medical News Today have associated e-cigarette use with increased cardiovascular risk and abnormal cardiac activity. Such studies have pointed to the nicotine in e-cigarette liquids as the likely cause.
The new study from Nystoriak and team provides further evidence of how e-cigarettes might harm the heart, but, this time, chemical flavorings are the offender.
Nystoriak and colleagues tested 15 different e-cigarette flavorings on human cardiomyocytes derived from induced pluripotent stem cells.
Cardiomyocytes are the cells that make up the heart muscle, and they are responsible for the contractile function of the heart, which enables the organ to pump blood around the body.
The team monitored how each flavoring — when heated and unheated — affected the function of cardiomyocytes.
"While many flavor chemicals are conventional food additives and generally regarded as safe," the researchers note, "little is known regarding their impact on human cardiac function. Moreover, how heating/combustion of these compounds affects their toxicity is completely unknown."
The team identified a number of flavorings that had different effects on cardiomyocyte functions.
They found that cinnamaldehyde, or cinnamon flavoring, prevented the cardiomyocytes from contracting 24 hours after coming into contact with them, while eugenol (clove), citronellol (floral), and limonene (citrus) caused the heart muscle cells to 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," says Nystoriak.
'Don't assume that e-cigarettes are harmless'
The researchers note that the flavorings that caused the greatest alterations to cardiomyocytes had the strongest effects when unheated.
However, there are thousands of flavorings for e-cigarette liquids, and the team points out that it is still unclear as to how many of these break down once heated.
One limitation of this study is that the experiments were completed in vivo, so precisely how inhaling the flavorings in e-cigarette liquids might impact cardiomyocyte function needs to be studied further.
Still, commenting on the team's findings, Matthew L. Springer, Ph.D. — who was not involved in the research but who studies the effects of tobacco smoke on vascular function — says that e-cigarette users should take these results into consideration.
"They should not assume that e-cigarettes are harmless just because they don't produce smoke. The best thing that you can inhale is clean air."