Preference and thermal comfort of a menthol mouth swill of differing concentrations in both temperate and hot environments: a randomised cross-over trial.

Abstract

Background: Menthol mouth swilling is a nutritional intervention that improves performance across different modes of exercise. A range of menthol concentrations are currently used because a preferred concentration has not yet been established; whether or not preference changes between differing thermal environments is also unknown. Objective: To determine the preferred concentration of a menthol solution and which concentration offers the most thermal comfort at rest in temperate and hot environments. Additionally, the study aimed to determine the preference of menthol solutions for those who use mouthwash compared to those who do not. Design: A randomised cross-over trial involving 50 consenting male and female participants was conducted in two different thermal environments, temperate (21 °C ) and hot (33 °C). In each trial, six menthol solutions (0.00, 0.01, 0.03, 0.05, 0.08 and 0.10% concentration) were swilled and individually rated for nine preference characteristics on a 100mm scale. Thermal comfort was rated before and after the swilling of each solution. Anthropometrical measurements were taken and participants’ habitual menthol use and liking of the taste of mint were determined. Results: A variation in preference was evident for menthol solutions between thermal environments. Significant dislike for all menthol concentrations was evident in the temperate environment in terms of overall pleasantness, however the most significant dislike was evident among 0.03, 0.08 and 0.10% menthol concentrations; the mean difference (95% CI) for 0.03% menthol concentrations was -13 (-20, -7), whilst both 0.08 and 0.10% menthol concentrations had the same mean difference (95% CI) of -13 (-19, -6). In the hot environment, only a significant dislike for the strongest concentration in terms of overall pleasantness was observed; the mean difference (95% CI) for 0.10% menthol concentration was -7 (-14, 0). Those who reported to use mouthwash demonstrated a significantly greater overall liking for the strongest menthol concentration (0.10%) compared to non-users, irrespective of temperature. However, menthol concentrations of 0.05% and 0.10% were most preferred in the temperate and hot environment, respectively; mean differences (95% CI) were 14.3 (4.7, 23.9) and 12.6 (2.4, 22.9). The menthol concentration of 0.08% provided a significant reduction in thermal comfort in both thermal environments; the mean difference (95% CI) in the temperate and hot environment was -0.4 (-0.7, -0.1) and -0.03 (-0.06, 0.0), respectively. Conclusion: No clear preference for a menthol concentration could be determined. The results from this study indicate that the thermal environment and habitual menthol use influence preference for menthol concentrations. These are important considerations for future researchers who are aiming to determine the most preferable menthol concentration in a sports and exercise setting