Effect of caffeine on the acceptability of flavoured drinks

Background: Research on the behavioural effects of caffeine is well documented and reviewed. One area rarely covered in the reviews is the effects of caffeine on the acceptability of novel drinks. Findings from such studies have been used to support the view that caffeine deprivation, and its reversal by the ingestion of caffeine, is a major mechanism underlying behavioural changes associated with caffeine. Methods: The present study continued this research on the repeated pairing of novel flavours with caffeine or placebo in groups differing in level of regular caffeine consumption (non-consumers, low consumers, and high consumers). Three groups of volunteers were recruited: non-consumers of caffeine (N=23); low consumers (<200mg/day; N=40) and high consumers (>300mg/day; N=33). After abstaining from caffeine overnight, the volunteers visited the laboratory at 09.00 andconsumed a fruit juice with either caffeine (100 mg) or placebo. The caffeine manipulation was double-blind. Participants rated the pleasantness of the drink after their initial taste and after they had consumed it. Two hours later, they returned to the laboratory and repeated the procedure with a fruit tea being consumed, again with or without caffeine. The procedure was repeated for five consecutive days. Results: The analysis of the fruit juice data showed that drink acceptability increased over days and decreased when caffeine was added to the drink. There were no interactions with consumer status. Similar results were found for the ratings of the fruit tea. In addition, those who had caffeine in the fruit juice rated the fruit tea as more acceptable. Again, there were no interactions with consumer status. Conclusion: These results do not confirm the previous finding that caffeine-deprived participants develop a dislike for novel drinks not paired with caffeine, nor that caffeine increases the liking of a novel drink consumed by caffeine-deprived individuals. Rather the results suggest that the taste of caffeine reduces the acceptability of the current drink and leads to an increased liking of a subsequent drink due to the contrast with the previous one.