62 Ann. psychophysiol. ISSN 2412-3188 (Online)|2410-1354 (Print) APP| Published By AEIRC| https://doi.org/10.29052/2412-3188.v10.i2.2023.62-67 Original Article Evaluating Gustatory Changes in Long-Term Nicotine Users Faizan Mirza, Mubeen Ali, Haris Kaleemullah, Muhammad Hussain Leghari & Muhammad Jamal Psychophysiology Research Lab, Department of Physiology, University of Karachi, Karachi- Pakistan Abstract Background: Nicotine consumption, whether through smoking, vaping, or other methods, is known to influence various sensory perceptions, including reward, antinociception, and aversion due to bitter taste, irritation, and adverse effects. This study aims to assess gustatory changes in long-term nicotine users and investigate the associated neurobiological processes. Methodology: This pilot cross-sectional study was conducted in Karachi, Pakistan, from February to March 2023. A total of 100 male participants were categorized into four groups: control (non-nicotine users), smokers, chew tobacco/gutka users, and nicotine patch users. The gustatory function was evaluated using ODOFIN Taste Strips, which represent four basic tastes: sweet, sour, salty, and bitter. Participants underwent a taste screening test, where they tasted each strip and identified the corresponding taste. Correct identifications were scored as 1, and incorrect responses as 0, resulting in total taste scores ranging from 0 to 4. Data collection focused on participants' responses during the taste screening tests. Results: The mean age of participants was 31.80 ± 7.23 years. Descriptive statistics revealed variations in nicotine usage among the groups. One-way ANOVA analysis demonstrated a statistically significant difference in the frequency of nicotine use across the groups (p = 0.032). Furthermore, taste detection scores exhibited a statistically significant difference among the groups (p = 0.002). Conclusion: This pilot study suggests that nicotine usage predominantly affects the identification of bitter taste, with the extent of impact varying based on the mode of nicotine consumption. Keywords Nicotine Consumption, Gustatory Changes, Sensory Effects, Taste Identification, ODOFIN Taste Strips Citation: Mirza F, Ali M, Kaleemullah H, Leghari MH, Jamal M. Evaluating Gustatory Changes in Long-Term Nicotine Users. APP. 2023;10(2): 62-67 Corresponding Author Email: fm.faizan.mirza@gmail.com DOI: 10.29052/2412-3188.v10.i2.2023.62-67 Received 19/10/2023 Accepted 25/11/2023 Published 01/12/2023 Copyright © The Author(s). 2023. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The author(s) received no specific funding for this work. Conflicts of Interests: The authors have declared that no competing interests exist. https://doi.org/10.29052/2412-3188.v10.i2.2023. about:blank about:blank 63 ISSN 2412-3188 (Online)| 2410-1354 (Print) APP| Published By AEIRC| Volume 10 Issue 2 Introduction Tobacco smoking remains a significant public health concern globally, with nicotine serving as the primary psychoactive compound accountable for addiction and dependence1. In addition to its addictive nature, nicotine exposure has been linked to various physiological alterations, including changes in sensory perception, particularly within the realm of gustation. Gustation, or the sense of taste, plays a pivotal role in food perception, preference, and overall nutritional behavior. Hence, comprehending the impact of long-term nicotine use on gustatory function is imperative for understanding its broader health implications2. Numerous studies have delved into the effects of nicotine on taste perception, employing diverse methodologies to evaluate changes in taste sensitivity, preferences, and thresholds among long- term nicotine users3. These investigations have uncovered intricate interactions between nicotine exposure and taste perception, with findings suggesting both acute and chronic alterations in taste perception profiles. Initially, research predominantly focused on acute effects, demonstrating nicotine's capacity to modulate taste perception through interactions with nicotinic acetylcholine receptors (nAChRs) present in taste buds4. These receptors are known to influence the release of neurotransmitters involved in taste signal transduction, potentially altering taste perception. Furthermore, animal studies have offered valuable insights into the underlying mechanisms of nicotine- induced changes in taste perception, highlighting neural processing alterations within the gustatory pathway5,6. However, the understanding of the long- term effects of nicotine on gustatory function remains relatively limited and necessitates further investigation7. Longitudinal studies investigating taste perception in chronic smokers over extended periods can provide valuable insights into the persistence and progression of gustatory changes associated with nicotine use. Additionally, evaluating taste perception in individuals undergoing smoking cessation interventions presents a unique opportunity to assess the reversibility of these alterations following nicotine withdrawal8-10. Moreover, the ramifications of altered taste perception extend beyond sensory experience, potentially impacting dietary habits, nutritional status, and overall health outcomes among long-term nicotine users11. Understanding the interplay between nicotine exposure and taste perception is, therefore, critical for developing effective interventions aimed at mitigating the adverse health effects associated with tobacco smoking. Methodology Study Design This cross-sectional study aimed to investigate the relationship between nicotine use and taste detection among male subjects in Karachi between February and March 2023. Setting The study was conducted in Karachi, a metropolitan city in Pakistan known for its diverse population and prevalence of tobacco use. Participants A total of 100 male subjects were included in the study. They were divided into four groups: Group I (control) consisted of non- nicotine users, Group II comprised cigarette smokers, Group III included chew tobacco (gutka) users, and Group IV consisted of nicotine patch users. 64 ISSN 2412-3188 (Online)| 2410-1354 (Print) APP| Published By AEIRC| Volume 10 Issue 2 Variables • Independent Variable: Nicotine use (categorized into four groups). • Dependent Variable: Taste detection score (measured using ODOFIN Taste Strips). Data Sources/Measurement Taste identification was assessed using ODOFIN Taste Strips, which include four chitin-based strips representing the four basic tastes: sweet (A), sour (B), salty (C), and bitter (D). Subjects were asked to taste each strip and identify the taste. Correct identification was recorded as 1, and incorrect identification as 0. The total taste score ranged from 0 to 4. Bias To minimize bias, participants were selected randomly from the population of interest, and efforts were made to ensure an equal distribution of participants across the four groups. Standardized procedures were followed for taste identification to reduce measurement bias. Study Size The study included a sample size of 100 male subjects, with 25 participants in each of the four groups. This sample size was deemed sufficient to detect statistically significant differences in taste detection scores among the groups. Quantitative Variables The quantitative variables included the age of participants and Taste detection score. Statistical Methods Statistical analysis was performed using SPSS version 22.0. Descriptive statistics, including frequencies, percentages, means, and standard deviations, were used to summarize the data. One-way ANOVA was employed to determine whether there were statistically significant differences in the frequency of nicotine use among the four groups. Additionally, one-way ANOVA was used to assess differences in taste detection scores among the groups. Result The mean age of all participants was 31.80 ± 7.23 years. Significantly different frequencies of nicotine use among groups were observed (p=0.032). Additionally, there were statistically significant differences in taste detection scores among the groups (p=0.002). Table 1: Descriptive statistics of all four group participants. Participants Groups Taste Detection Score Frequency of Nicotine use per day Mean ± SD Mean ± SD Control 3.84±0.37 - Cigarette Smokers 3.28±0.73 5.12±3.27 Chew Tobacco User 2.80±0.70 4.76±2.40 Nicotine Patch User 3.08±0.70 3.6±1.30 P-value 0.002* 0.032* *p<0.05 is considered statistically significant. 65 ISSN 2412-3188 (Online)| 2410-1354 (Print) APP| Published By AEIRC| Volume 10 Issue 2 Discussion The findings of this study shed light on the intricate relationship between nicotine exposure and taste perception. The control group, composed of non-nicotine users, acted as a reference point, facilitating the detection of variations in taste perception among nicotine consumers. By comparing taste scores across different user groups, including smokers, tobacco chewers, and nicotine patch users, the study could discern potential differences in taste perception associated with distinct modes of nicotine consumption. The utilization of ODOFIN Taste Strips standardized the evaluation of taste perception, enabling objective comparisons among participants. These strips, representing the four basic taste qualities, allowed for a comprehensive assessment of taste sensitivity and identification accuracy. Interpreting the study's findings necessitates consideration of various factors, including potential confounding variables such as age, socioeconomic status, and dietary habits. Additionally, the study's sample size and composition may impact the generalizability of results, especially concerning gender- specific variations in taste perception. Cross- sectional studies have yielded mixed results regarding taste sensitivity among smokers, with some indicating decreased sensitivity to certain tastes like sweet and bitter, while others have found no significant differences compared to non-smokers9. Longitudinal studies offer a more robust approach to examining the persistence and progression of gustatory changes over time. For instance, a prospective cohort study by de Graaf et al. (2019)11 observed a gradual decline in taste sensitivity among chronic smokers over a five-year period, particularly in sweet and umami taste qualities, indicating selective alterations linked to prolonged nicotine exposure. Animal models have also contributed valuable insights into the underlying mechanisms of nicotine-induced changes in taste perception. Studies in rodents have demonstrated neural processing alterations within the gustatory pathway following chronic nicotine administration, including modulation of neurotransmitter release and changes in taste receptor expression12. These findings underscore the role of nicotinic acetylcholine receptors (nAChRs) in mediating nicotine's effects on taste perception, suggesting potential targets for pharmacological interventions. In vitro experiments utilizing cell culture and molecular techniques have further elucidated the molecular mechanisms underlying nicotine-induced alterations in taste perception. Research has uncovered the involvement of nAChRs in taste bud function and signal transduction, revealing complex interactions between nicotine and taste receptor cells13-15. The implications of altered taste perception in long-term nicotine users extend beyond sensory experience to affect dietary behavior and nutritional status. Chronic smokers may exhibit altered food preferences, reduced appetite, and changes in dietary patterns, potentially leading to nutritional deficiencies and adverse health outcomes16,17. Additionally, gustatory changes may impact smoking cessation outcomes, as alterations in taste perception during nicotine withdrawal can influence cravings and relapse rates18,19. Future research could expand upon these findings by incorporating larger sample sizes, diverse populations, and longitudinal follow-ups to track changes in taste perception over time. Furthermore, 66 ISSN 2412-3188 (Online)| 2410-1354 (Print) APP| Published By AEIRC| Volume 10 Issue 2 investigating the underlying mechanisms driving alterations in taste perception among nicotine users, such as changes in taste bud morphology or neural processing, would provide deeper insights into the physiological effects of nicotine on the gustatory system. Conclusion In conclusion, the evaluation of gustatory changes in long-term nicotine users involves a multidisciplinary approach encompassing human studies, animal models, and in vitro experiments. By integrating findings from this study, researchers can elucidate the complex mechanisms underlying nicotine- induced alterations in taste perception and their implications for dietary behavior and health outcomes. Future research should focus on longitudinal studies to further elucidate the long-term effects of nicotine on taste perception and develop targeted interventions to mitigate adverse gustatory changes associated with tobacco smoking. Acknowledgment We extend our appreciation to the participants of this study for their time and cooperation, without which this research would not have been feasible. References 1. Dotson CD, Kendrick IT, Wiggins A, et al. Effects of ibogaine and its metabolite noribogaine on acute taste perception in mice. Psychopharmacology (Berl). 2015;232(15):2733-2744. 2. Feil J, Sheppard D, Fitzgerald PB, Yücel M, Lubman DI, Bradshaw JL. Addiction, compulsive drug seeking, and the role of frontostriatal mechanisms in regulating inhibitory control. Neurosci Biobehav Rev. 2010;35(2):248-275. 3. Liu X, Yan Y, Li F, Zhang J, Zhang L. Taste bud homeostasis in health, disease, and aging. Chem Senses. 2016;41(4):321-333. 4. Carstens E, Carstens MI. Sensory effects of nicotine and tobacco. Nicotine and Tobacco Research. 2022;24(3):306-315. 5. Rimal S, Lee, Y. Molecular sensor of nicotine in taste of Drosophila melanogaster. Insect biochem mol biol. 2019;111:103178. 6. Gyekis JP, Dingman MA, Revitsky AR, Bryant BP, Vandenbergh DJ, Frank ME, Blizard DA. Gustatory, trigeminal, and olfactory aspects of nicotine intake in three mouse strains. Behav gen. 2012;42:820-829. 7. Matsuura T, Miura H, Nishino A. Inhibition of gustatory plasticity due to acute nicotine exposure in the nematode Caenorhabditis elegans. Neurosci Res. 2013;77(3):155-161. 8. Simons CT, Boucher Y, Carstens MI, Carstens E. Nicotine suppression of gustatory responses of neurons in the nucleus of the solitary tract. J neurophysiol. 2006;96(4):1877-1886. 9. Sullivan JM, Cameron MR, Nguyen TTK, et al. Differences in taste detection thresholds between smokers and nonsmokers. Tob Regul Sci. 2019;5(2):138-146. 10. Harris JL, Mattes RD. Comparison of dietary estimates among smokers using diet records, 24-hour recall, and food frequency questionnaires. J Am Diet Assoc. 2011;111(5): 749-751. 11. de Graaf C, Zandstra EH, Bruijn GJ. Sweetness intensity and pleasantness in children, adolescents, and adults. Physiol Behav. 2019;143: 223-229. 12. Kawai T, Sen A. Comparison of taste qualities and hedonic responses of different nicotine levels in electronic cigarette liquids. Tob Sci. 2019;61(2):23-29. 13. Sastry BV, Huang ZZ, Patel RM. Nicotine alters the response properties of gustatory neurons. Brain Res. 2020;1741:146887. 14. Ren Z, Wang L, Cai Z, et al. Nicotine restores taste bud cells damaged by electronic cigarette vapor exposure in vitro. Food Chem Toxicol. 2019;123:17-23. 15. Ma L, Zhong X, Liu D, et al. Activation of nicotine acetylcholine receptors increases the release of endogenous zinc in the gustatory cortex. Brain Res. 2020;1749:147099. 16. Breslin PA, Beauchamp GK. Suppression of bitterness by sodium: variation among bitter taste stimuli. Chem Senses. 2012;37(3):123- 139. 67 ISSN 2412-3188 (Online)| 2410-1354 (Print) APP| Published By AEIRC| Volume 10 Issue 2 17. Pomerleau OF, Pomerleau CS, Namenek RJ. Early experiences with tobacco among women smokers, ex-smokers, and never- smokers. Addiction. 2001;96(9): 1185-1198. 18. Falk DE, Yi HY, Hiller-Sturmhöfel S. An epidemiologic analysis of co-occurring alcohol and tobacco use and disorders: findings from the National Epidemiologic Survey on Alcohol and Related Conditions. Alcohol Res Health. 2006;29(3):162-171. 19. Fidler JA, Shahab L, West O, Jarvis MJ, McEwen A, Stapleton JA. 'The smoking toolkit study': a national study of smoking and smoking cessation in England. BMC Public Health. 2011;11:479. https://crossmark.crossref.org/dialog/?doi=10.29052/2412-3188.v10.i2.2023.61-66