The debate over e-cigarette safety continues as evidence of potential harm mounts. A recent study exposed mice to flavored e-liquids, revealing risks to heart rhythm.
In October 2020, the independent Cochrane organization reviewed studies on e-cigarettes, finding smokers more likely to quit within six months using them. However, long-term health impacts remain unclear. Short-term benefits for quitting tobacco are evident, but effects on overall health—especially among teens, who make up nearly half of users drawn to the vast array of flavors—warrant caution.
These flavors are added to a base of 70% vegetable glycerin and 30% propylene glycol, with or without nicotine. A November 20, 2020, study in Heart and Circulatory Physiology by University of South Florida researchers demonstrated the toxic effects of specific flavors on heart cells (cardiomyocytes).
The team tested three e-liquids: one with passion fruit, orange, and guava; another mimicking vanilla custard; and a third blending cinnamon and apple cereal. In vitro experiments on mouse cardiomyocyte cultures showed these caused cell death via apoptosis or necrosis, with vanilla custard proving most toxic.
They then exposed human cardiomyocytes to vapor from the vanilla liquid, assessing electrical activity. Solvent-only vapor had no effect, but nicotine reduced it—and adding the flavor intensified the disruption.
“This experiment has shown us that flavoring chemicals added to vaping devices can increase harm beyond what nicotine alone can do.” — Sami Noujaim, study co-author, in a press release.
These disruptions appeared in vivo too: young mice exposed to vanilla vapor in a chamber for 10 weeks (5 hours daily) developed cardiac arrhythmia—irregular intervals between heartbeats. Researchers suggest vaping impairs the heart's autonomic nervous system, which regulates rhythm. Human studies are needed next.
