School of Psychology and Counselling, Queensland University of Technology, Beams Road, Carseldine, Queensland 4032, Australia
Received 4 February 2003; in revised form 1 April 2003; accepted 2 April 2003
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ABSTRACT |
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INTRODUCTION |
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To address the problems associated with the incidence of WKS in Australia the Australian National Health and Medical Research Council (NHMRC) (Gold et al., 1985; NHMRC, 2001
) requires all bread flour to be fortified with thiamine. The addition of thiamine to bread flour since 1991 is believed to be at least partly responsible for reducing the rate of WKS at necropsy from 4.7% to 1.1% (Harper et al., 1998
). Nonetheless, the Australian Institute of Health and Welfare reported that
1500 patients will be admitted to public psychiatric facilities each year with possible indications of WKS (Australian Institute of Health and Welfare, 2001
, 2002
). Clearly, while the fortification of bread flour with thiamine may have contributed to a reduction in the incidence of WKS, a large number of people remain at risk of WKS. This may be because of limitations inherent in this thiamine-delivery strategy, and raises the question of whether additional thiamine supplementation strategies are needed.
A key limitation of the thiamine bread-flour fortification strategy appears to be the amount of bread that needs to be eaten by heavily alcohol-dependent persons. For example, although the minimum daily thiamine requirement for neural integrity is thought to be 0.5 mg (Brody, 1999; Eitenmiller and Landen, 1999
), the consensus is that two-thirds of orally ingested thiamine is not absorbed or processed into its usable form by heavy alcohol users (Price and Kerr, 1988
; Victor et al., 1989
; Harper et al., 1998
; Todd et al., 1999
). Based on the legislated minimum of 6.4 mg thiamine/kg of bread flour, it is estimated that at least half of a 680 g loaf of bread would need to be consumed each day by a heavily alcohol-dependent person to prevent thiamine deficiency (Harper et al., 1998
), This level of bread consumption would seem to be particularly unlikely, at least in some alcohol-dependent persons who do not appear to eat regularly (Price and Kerr, 1985
; Price et al., 1991
; Stacey and Sullivan, 2002
). Arguably, those most in need of thiamine supplementation will remain at risk of WKS despite the apparent benefits of bread-flour fortification and despite the apparent benefits of this strategy in reducing the incidence of WKS. Thus, a complementary population-based prophylactic intervention may be needed to increase thiamine intake, and this could take the form of direct supplementation of thiamine to alcoholic beverages, as has been suggested previously (Wood et al., 1986
; Yellowlees, 1986
; Price and Kerr, 1988
; Harper et al., 1998
).
There are two recommended levels of thiamine fortification for alcoholic beverages. The NHMRC recommended that alcoholic beverages be overdosed with sufficient thiamine (0.1 mg/standard serving) to ensure brain health based on those drinking at hazardous levels (Gold et al., 1985). Alternatively, the National Research Committee (1989)
recommended that fortification should supply thiamine in proportion to the metabolic load of energy (alcohol) consumed,
0.35 mg/ 1000 kcal. However, Price and Kerr (1989)
and Harper et al. (1998
) argued that these recommendations under-estimate the thiamine requirements of heavy alcohol users, due to genetic differences in metabolic efficiency, digestive health, and how well thiamine is absorbed, processed and stored. They suggested that at least six times the recommended ratio would be required to metabolize the large quantities of calories (>5000 cal) commonly ingested by those heavily dependent on alcohol. A chronic alcohol user consuming 30 standard servings of alcohol per day should receive
10 mg of thiamine, which should ensure saturation and prevent the development of WKS.
Several studies have been published on the consumer acceptability of, and public support for, alcoholic beverage fortification with various forms of thiamine (Price, 1981; Budge and Price, 1982
; Crane and Price, 1983
; Price and Kerr, 1989
; Nixon et al., 1991
). Price and colleagues conducted several experiments examining consumer acceptability of thiamine-fortified beverages, and concluded that drinkers could not reliably differentiate between thiamine-fortified and normal beers at many times the 1.5 mg recommended daily allowance (up to 27.4 mg thiamine per 100 ml of beer) (Price, 1981
). Taste tests of thiamine in wine were less successful, with thiamine negatively affecting subjects taste preferences (Nixon et al., 1991
). Public opinion towards the thiamine-fortification proposal was almost unanimously supportive (Budge and Price, 1982
). These taste tests examined subjects preference for one of two samples, A or B. Participants chose beer samples equally and thus, Price (1981)
determined that there was no taste preference for either beer, and that thiamine had no effect on taste. However, few participants chose the no preference option, suggesting that most participants preferred either thiamine-fortified or regular beer, and that thiamine might influence beer preference.
The previous research by Price and colleagues on the feasibility of adding thiamine is interesting, but now at least a decade old. Patterns of drinking, dietary behaviours and attitudes to safe drug-taking appear to have changed since then (Australian Institute of Health and Welfare, 1998; Oboler et al., 2002
; Stylianou, 2002
; Weitzman et al., 2003
), raising questions about the extent to which these early findings may be generalizable today. Additionally, other beer characteristics (such as appearance) were not considered in previous thiamine-fortified beer research (Price, 1981
), and these may be important. Finally, previous investigations were not conducted in a double-blind manner (Price, 1981
); therefore, the findings from previous research need to be explored using more rigorous experimental methodology.
The aims of the present study were therefore to determine whether thiamine could be detected in beer in a contemporary sample and whether it altered subjective beer characteristics. Consistent with previous research (Price, 1981), it was predicted that thiamine would not be detected in beer. A further hypothesis that thiamine might alter beer characteristics sufficiently for participants to distinguish between samples was also explored.
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SUBJECTS AND METHODS |
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Apparatus and materials
Tasting booth. The taste test was conducted in a tasting booth constructed for the purpose of this experiment. The booth consisted of three walls. A curtain separated the booth from an assistant who was engaged in preparing beer samples. Participants stood at the booth in front of a desktop. The temperature of the booth was controlled (24 ± 2°C) to standardize tasting conditions between participants, and was measured periodically. The booth was illuminated by diffused overhead fluorescent strip battens that were adjusted to 560 lx (booth empty) and monitored to ensure the minimum standard for lighting (400 lx) for general laboratories (Standards Australia, 1990
) when the booth was occupied.
Inside the booth, on the desktop and to the participants right were placed a copy of the beer rating scales (BRS; see below) and a pencil. On the left, labels marked A, B or C were placed on the desk to denote where the (otherwise unmarked) beer samples were presented. A slotted box for depositing completed questionnaires was located outside of the booth.
Beer samples. The beer was commercially packaged XXXX Gold Lager, Queenslands market-share leader (Lion Nathan, 2000), in 375 ml bottles produced by Castlemaine Perkins, Milton. The beer was medium strength (3.6% alcohol by volume) and one 375 ml bottle contained approximately one standard serve (10 g) of alcohol. The beer was stored at 4 ± 2°C prior to serving, as recommended by the brewery, and was removed from refrigeration, dispensed and served to participants within
2 min. A pilot test found that the beer temperature rose from
4 to 6°C over 5 min after serving, within the recommended temperature range. Transparent cups allowed a clear view of the sample so as to rate its visual characteristics.
Two types of beer samples were prepared: thiamine-enriched and non-thiamine enriched (normal) beer samples. To prepare thiamine-enriched beer samples, thiamine HCl was added to an empty transparent cup at the required dose (10 mg in 0.1 ml of water) prepared by Sigma (Beta-Sol 100 mg in 1 ml ampoules). Beer was then added to the 100 ml mark. Beer samples for each participant were taken from the same bottle to ensure consistency. The concentration of thiamine used in this study was selected for comparability with Prices study (Price, 1981), and because it is considered a clinically relevant dose (Brody, 1999
; Whitney and Rolfes, 2002
). It should be noted, however, that there is ongoing debate about the level to which alcoholic beverages should be fortified with thiamine (see above).
Questionnaire: the beer rating scales (BRS). The BRS was constructed for this study and is shown in Appendix 1. This measure was developed to assess participants ratings of beer characteristics. Beer characteristics listed on the BRS have been examined in previous research, and included colour, mouthfeel, bubbliness, refreshingness, head quality, clarity, bitterness and overall taste (Price, 1981
; Guinard et al., 1998
; Lion Nathan, 2000
).
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The layout of the BRS was such that the first three pages of the scale comprised eight beer characteristic questions printed on one page. Separate pages were used to assess participants rating of each beer sample, to reduce cross-referencing between samples. The final page comprised multiple-choice questions. Question 25 asked the participant to choose the different sample and question 26 asked them to choose their preferred sample. Participants were given standardized instructions verbally and these instructions were printed on the BRS.
Design
This study was a mixed design with participants randomly allocated by an assistant to one of three independent groups (no thiamine sample, one thiamine sample and two thiamine samples). Data from participants in conditions B and C were used in analyses reported in this study (n = 32), since these participants consumed both types of beer, whereas participants in condition A received three 100 ml samples of beer, none of which contained thiamine. The repeated measures portion of the study required participants to independently rate each of the three 100 ml samples. The study was double-blind to prevent experimenter and participant bias.
Procedure
Each participant was interviewed for the study prior to taste testing so that informed consent could be obtained and demographic data collected. The participant entered the booth and was instructed by the researcher to drink three beer samples (labelled A, B and C). As stated previously, each sample contained either 0 or 10 mg thiamine HCl. Participants in condition A received three 100 ml samples of beer, none of which contained thiamine. Participants in condition B received three 100 ml samples of beer, two of which contained no thiamine and one of which contained 10 ml thiamine (total thiamine consumed by participants in this condition = 10 mg). Participants in condition C received three 100 ml samples of beer, one of which contained no thiamine and two of which contained 10 mg thiamine each (total thiamine consumed by participants in this condition = 20 mg). The position of the beer samples was counterbalanced to prevent practice and fatigue effects, and the habituating effect of alcohol on taste.
Once in the booth, participants were asked to rate each beer sample separately, fully consuming each sample and completing the rating scales before continuing to the next sample. Participants were instructed to begin at sample A, and whilst drinking sample A rate this beer on sample As rating scales. When sample A had been consumed and the ratings completed, they were to fold this page and place it in the slotted box. They were instructed to follow the same procedure for each sample. This procedure was adopted to prevent referencing between samples. Participants were then instructed to complete the final page of the BRS and place this in the box.
Statistical analyses
The data from the VAS for conditions B and C were analysed with paired samples t-tests comparing subjects responses for thiamine and non-thiamine samples for each beer characteristic (BRS items 124). Question 25 on the BRS (Which beer is different from the others?) was analysed with a single sample t-test with the test value set at 1.33. Note that the data from participants in condition A had no correct choice for question 25 (i.e. all beer samples were non-thiamine enriched), and data from this condition were therefore excluded from this BRS analysis. Question 26 (Which beer do you prefer?) was analysed descriptively and the data from those participants indicating a beer preference was subjected to a single sample t-test. An alpha of 0.05 was used in all analyses.
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RESULTS |
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BRS beer characteristic data were then analysed using paired samples t-tests, which compared participants ratings of each beer characteristic for thiamine and non-thiamine beer. Results from these analyses are shown in Table 1, together with participants mean ratings for each beer characteristic. Table 1 shows participants did not rate thiamine and non-thiamine beer samples as significantly different in terms of taste, colour, mouthfeel, bubbliness, refreshingness, head and clarity. Bitterness was the only beer characteristic that reached statistical significance, with participants rating thiamine-enriched beer significantly more bitter than non-thiamine enriched beer. Participants also rated the thiamine-fortified beer as poorer tasting than the non-thiamine beer, but this did not reach statistical significance [t(31) = 2.021, P = 0.052, 2 = 0.116]. It is possible that the significant difference in bitterness may have contributed to this taste characteristic and that this is not a chance result.
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DISCUSSION |
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The second hypothesis for this study was exploratory and examined whether the fortification of beer with thiamine would alter the measured characteristics of beer. Analysis of the BRS returned only one significant finding, namely, that thiamine-fortified beer was significantly more bitter that non-thiamine fortified beer. Participants did not rate any of the beer characteristics tested in this study as significantly different. While fortified beer was rated more bitter, participants failed to identify beer fortified with up to 10 times the recommended commercial concentration of thiamine. Fortifying beer at the lower thiamine concentrations may reduce the bitterness effect observed in this study although this has yet to be demonstrated. However, if lower concentrations of thiamine can be added to beer without altering bitterness perception, this might further reduce the likelihood that consumers might be able to discriminate between fortified and normal beer based on differences in bitterness perception. Future research should explore trends in bitterness and taste using thiamine concentrations ranging from 0 mg to 10 mg/100 ml of beer.
Preferences for thiamine-fortified beer and normal beer were similar to those found by Price (Price, 1981). Participants indicated a slight, but not significant preference for normal beer, with 1 in 5 indicating no preference for one sample over the other. As bitterness was the only beer characteristic that reliably distinguished between samples in this study, these results may reflect individual differences in preferences for bitter tasting substances. This might be further examined by controlling for P perception of, and preference for bitter tasting substances.
These findings refute the arguments against thiamine fortification put forth by brewers during NHMRC deliberations (Gold et al., 1985). Although thiamine was detectable at the concentration used in this study (if differences in the perception of bitterness are used as an index of the presence of thiamine), participants could not reliably distinguish between fortified and non-fortified beers. Whether thiamine is detectable in beer, and whether it negatively alters the taste of beer, has implications for the support and success of any fortification intervention. Trials of beers fortified at commercial concentrations are recommended as a possible complementary prophylaxis for WKS.
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ACKNOWLEDGEMENTS |
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FOOTNOTES |
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