E-cigarette Flavors, Sensory Perception, and Evoked Responses

Abstract

The chemosensory experiences evoked by flavors encompass a number of unique sensations that include olfactory stimuli (smell), gustatory stimuli (taste, i.e., salty, sweet, sour, bitter, and umami (also known as “savoriness”)), and chemesthesis (touch). As such, the responses evoked by flavors are complex and, as briefly stated above, involve multiple perceptive mechanisms. The practice of adding flavorings to tobacco products dates back to the 17th century but is likely much older. More recently, the electronic cigarette or “e-cigarette” and its accompanying flavored e-liquids emerged on to the global market. These new products contain no combustible tobacco but often contain large concentrations (reported from 0 to more than 50 mg/mL) of nicotine as well as numerous flavorings and/or flavor chemicals. At present, there are more than 400 e-cigarette brands available along with potentially >15,000 different/unique flavored products. However, surprisingly little is known about the flavors/flavor chemicals added to these products, which can account for >1% by weight of some e-liquids, and their resultant chemosensory experiences, and the US FDA has done relatively little, until recently, to regulate these products. This article will discuss e-cigarette flavors and flavor chemicals, their elicited responses, and their sensory effects in some detail.

Fruit flavors in electronic cigarettes (ECIGs) are associated with nocturnal dry cough: A population longitudinal analysis

“…Flavors in ECIGs evoke chemosensory experiences that has been associated with initiation, progression and dependence or addiction to ECIGs products among youth, young adults, and never smokers [ 47 , 48 ]. Flavors enhance the palatability of high concentrations of ECIGs constituents, such as nicotine, PG and VG [ 15 , 49 , 50 ].…”

Nicotine flux as a powerful tool for regulating nicotine delivery from e-cigarettes: Protocol of two complimentary randomized crossover clinical trials

“…Indeed, the appeal and prevalence of EC among youth are usually attributed to several factors including flavoring, customizability, and effective nicotine delivery [5][6][7][8][9][10]. While there is strong reason to believe that flavors contribute to EC appeal in youth, [11][12][13] sustained use could be attributed to efficient nicotine delivery [14]. Early EC devices (i.e., cig-a-like) were flavored yet delivered little or no nicotine to the user and their use was not sustained [15].…”

Adverse Biophysical Impact of e-Cigarette Flavors on Pulmonary Surfactant

“…Reportedly, there are ∼17,000 flavored e-liquid products available on the market from over 450 retail brands. − These flavors can be grouped into 12 categories, i.e., tobacco, menthol/mint, nuts, spices, coffee/tea, alcohol, other beverages, fruit, dessert, candy, other sweets, and others . Although most of the flavoring chemicals used in e-liquids are considered safe for ingestion by the Flavors and Extract Manufacturers Association (FEMA), this assessment is not necessarily valid for inhalation. − In accordance with flavor variety and attractiveness among youth, there has been a vast emergence of research on the pulmonary toxicity of e-cigarette flavors. − A collection of in vitro studies have identified a dose-dependent toxicological effect of common flavoring ingredients used in commercial e-liquids, including maltol, ethyl maltol, vanillin, and cinnamaldehyde, on human respiratory cells. − Likewise, benzaldehyde is a primary ingredient in many cherry flavored e-liquids, yet it is a known respiratory irritant with potential to cause acute lung injury. , Studies have also found flavored e-liquids to produce reactive oxygen species (ROS) when vaporized, which can impair blood vessels, thus increasing the risk of developing cardiovascular diseases .…”