Sensory Effects of Menthol and Nicotine in an E-Cigarette

Abstract

Introduction: Despite the longstanding use and popularity of menthol as a flavorant in tobacco products, its sensory interactions with inhaled nicotine have never been measured independently of the other irritants in tobacco smoke. We therefore measured the perception of menthol in an E-cigarette with the primary goal of assessing its analgesic effect on the sensory irritation produced by inhaled nicotine.

Methods: Adult cigarette smokers sampled aerosolized E-liquids containing five different concentrations of nicotine with 0%, 0.5%, or 3.5% l-menthol, as well as two commercial menthol flavors with and without nicotine. For each of the E-liquids participants used a labeled magnitude scale to rate the Overall Sensation intensity, Coolness/Cold, and Irritation/Harshness they experienced, and a Labeled Hedonic Scale to indicate how much they liked/disliked the overall flavor.

Results: The main findings were that (1) perceived Irritation/Harshness was unaffected by a low (0.5%) menthol concentration, whereas a high menthol concentration (3.5%) led to higher perceived Irritation/Harshness at low nicotine concentrations but to lower Irritation/Harshness at the highest nicotine concentration (24mg/ml); (2) a commercial Menthol-Mint flavor produced similar results; (3) nicotine tended to enhance rather than suppress sensations of Coolness/Cold; and (4) menthol tended to slightly increase liking independently of nicotine concentration.

Conclusion: In addition to adding a sensation of coolness, menthol can reduce perceived airway irritation and harshness produced by inhalation when nicotine concentration is high, and contributes to the sensory impact of E-liquids when nicotine concentration is low.

Implications: The evidence presented here indicates that menthol can potentially improve the appeal of E-cigarettes not only via its coolness and minty flavor, but also by reducing the harshness from high concentrations of nicotine. As the first direct demonstration of an analgesic effect of menthol on inhaled nicotine in humans, these data also have implications for the role of menthol flavors in other inhaled tobacco products.

Figure 1.

Log₁₀ mean ratings of Overall sensation intensity as a function of nicotine concentration (0, 6, 12, 18, 24mg/ml) in E-liquids containing 3.5%, 0.5%, or 0% menthol. Letters on the right y-axis denote semantic labels of sensation intensity on the general Labeled Magnitude Scale (gLMS): BD = Barely Detectable; W = Weak; M = Moderate; S = Strong. Error bars represent the standard errors of the means (SEM).

Figure 2.

Log₁₀ mean ratings of Coolness/Cold sensations as a function of nicotine concentration (0, 6, 12, 18, 24mg/ml) in E-liquids containing 3.5%, 0.5%, or 0% menthol. Letters on the right y-axis denote semantic labels of sensation intensity on the general Labeled Magnitude Scale (gLMS): BD = Barely Detectable; W = Weak; M = Moderate; S = Strong. Error bars represent the standard errors of the means (SEM).

Figure 3.

Log₁₀ mean ratings of Irritation/Harshness perceived during inhalation of E-liquid aerosols as a function of nicotine concentration (0, 6, 12, 18, 24mg/ml) in E-liquids containing 3.5%, 0.5%, or 0% menthol. Letters on the right y-axis denote semantic labels of sensation intensity on the general Labeled Magnitude Scale (gLMS): BD = Barely Detectable; W = Weak; M = Moderate; S = Strong. Error bars represent the standard errors of the means (SEM).

Figure 4.

Shown are Log₁₀ mean ratings of Overall sensation, Coolness/Cold, and Irritation/harshness reported for two concentrations of nicotine (0 and 24mg/ml) and three E-liquid flavors: No Menthol (light grey bars), Menthol (grey bars), and Menthol–Mint (black bars). For each sensation the bars having different letters (a–d) are significantly different from one another. Letters on the right y-axis denote semantic labels of sensation intensity on the general Labeled Magnitude Scale (gLMS): BD = Barely Detectable; W = Weak; M = Moderate; S = Strong. Error bars represent the standard errors of the means (SEM).