Elsevier

Drug and Alcohol Dependence

Volume 60, Issue 2, 1 August 2000, Pages 199-206
Drug and Alcohol Dependence

Bitter and sweet components of ethanol taste in humans

https://doi.org/10.1016/S0376-8716(99)00149-0Get rights and content

Abstract

This study examined taste descriptions elicited by ethanol and by other tastants in humans. All subjects described 10% ethanol as bitter and ≈30% of the subjects described it as sweet and/or sour. Highly significant correlations were found between sweetness of some sucrose solutions (0.6–1%) and intensity of the taste of ethanol. In another experiment, quinine (bitter) solutions were rated as similar to 10% ethanol taste and this effect was potentiated by the addition of sucrose. In contrast, citric acid (sour) tended to decrease similarity ratings when added to the quinine solutions. Taken together, these findings suggest that: (1) in humans ethanol tastes both bitter and sweet; and (2) the relationship between sucrose and ethanol intakes previously found in animals and humans may result, at least partially, from similar taste responses elicited by sucrose and ethanol.

Introduction

It has been repeatedly reported that rodents with a high preference for sweet substances (e.g. saccharin or sucrose) consume more ethanol (alcohol) than rats or mice with a low preference for these substances (Gosnell and Krahn, 1992, Bachmanov et al., 1996; for review, see Kampov-Polevoy et al., 1999). The above correlation has been reported for both genetically selected alcohol preferring (Sinclair et al., 1992, Stewart et al., 1994, Kampov-Polevoy et al., 1996) and outbred strains of rats (Gosnell and Krahn, 1992, Koros et al., 1998, Kampov-Polevoy et al., 1999). The interaction between the intake of sweet substances and the preference for ethanol seems not to be limited to rodents. An increased ethanol intake among adolescents was correlated with an increased intake of sugars and sweets (Yamamoto et al., 1991). More recently, Kampov-Polevoy et al. (1997) have found that compared to controls, more alcoholic subjects preferred high sucrose concentrations.

At least two hypothesis could explain the mechanism of association between sweets consumption and alcohol drinking. First, one could speculate that a common neurochemical substrate in the CNS mediates rewarding properties of sweets and ethanol (Kampov-Polevoy et al., 1999). For example, there is a growing body of evidence linking excessive consumption of sweets and alcohol to the brain opioid system (Lynch, 1986, Gosnell and Majchrzak, 1989, Herz, 1997, Bienkowski et al., 1999).

The second hypothesis deals with peripheral taste factors. Ethanol-associated taste cues have been repeatedly proposed to determine ethanol drinking behaviour especially in alcohol-naive individuals (Richter, 1941, Fromme and Samson, 1983, Di Lorenzo et al., 1986). In line with the above suggestions, Samson et al. (1989) have shown that first exposure to ethanol taste is aversive in more than 40% of men and women and that this aversive response tends to predict future abstinence. Electrophysiological and behavioural studies in non-human subjects have suggested that ethanol taste has both bitter and sweet components (Di Lorenzo et al., 1986, Kiefer and Lawrence, 1988, Hellekant et al., 1997). Also preliminary experiments with human subjects have revealed that low ethanol concentrations may produce some sweet sensations (Wilson et al., 1973). Given the above, one could assume that the relationship between sweets preference and ethanol intake results, at least partially, from similar taste responses to sweets and alcohol (for recent discussion, see Bachmanov et al., 1996).

The purpose of the present study was twofold. First, we aimed to examine descriptive responses to ethanol taste in healthy human volunteers. For this reason two experiments were done. In experiment 1, participants described taste sensations produced by different concentrations of ethanol. In experiment 2, the subjects assessed similarity of tastant mixtures to ethanol.

The second aim of the present study was to search for correlations between responses to sucrose and ethanol taste. Thus, in experiment 1 reactivity to sucrose taste was also analysed.

Section snippets

Subjects

Twenty healthy volunteers (eight males, 12 nonpregnant females) participated in the study. All subjects consumed at least one standard drink per week and were classified as social drinkers. Eight participants were also regular cigarette smokers. Their mean (±S.D.) Fagerström Tolerance Questionnaire (Fagerström, 1978) score was 3.5 (±1.2). Table 1 presents basic characteristics of the participants including parameters of cigarette consumption in the smoking group.

Candidates for the study were

Intensity and pleasantness of sucrose and ethanol taste — effects of gender and smoking status

The ANOVA did not reveal any effect of gender or smoking status on responses to either ethanol or sucrose solutions (all Fs<1, Ps>0.2; data not shown).

Fig. 1 presents mean intensity (A,B) and pleasantness (C,D) of the taste of different sucrose and ethanol concentrations. In addition, number of subjects assigning highest pleasantness score to a given concentration is shown in parentheses.

Subjective evaluation of ethanol taste

All subjects identified bitter sensations in the taste of ethanol samples. For example, 10% ethanol, i.e.

Discussion

In agreement with previous reports (Weizenbaum et al., 1980, Hyde and Feller, 1981, Kunka et al., 1981; but see also Conner and Booth, 1988), there were no major differences in responses to sweet taste between males and females in the present study. Similarly, we did not find any differences in sweet taste reactivity between smokers and non-smokers. Several investigators have shown that smoking status does not alter sweet taste intensity (Peterson et al., 1968, Redington, 1984, Perkins et al.,

Acknowledgements

This study was supported by PARPA (grant Alc 18/99) and the State Committee for Scientific Research (KBN grant no. 4 PO5A 083 17).

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