Caffeine reinforces flavour preference in caffeine-dependent, but not long-term withdrawn, caffeine consumers

Previous studies have shown that caffeine can reinforce flavour liking in overnight deprived moderate caffeine consumers (e.g. average of 250 mg/day) but not in low consumers (<120 mg/day). However, it is not possible to determine whether the difference between moderate and low caffeine consumers results from pre-existing individual differences in response to caffeine, or results directly from the different amounts of caffeine they habitually consume. If the former were true, then moderate consumers who are completely withdrawn should still manifest the flavour conditioning effect. Conversely, if the latter were true, consumers who are completely withdrawn should not manifest the effect.

To examine whether moderate caffeine consumers who have been fully withdrawn from caffeine manifest the flavour conditioning effect.

In a double-blind study, 48 moderate caffeine consumers refrained from consuming caffeine for 4 weeks and were given replacement drinks to consume, which were either caffeinated (maintained group) or decaffeinated (withdrawn group). In the final 2 weeks, all subjects evaluated a novel drink containing either 100 mg caffeine or placebo on four non-consecutive days. RESULTS. The rated pleasantness of the novel drink containing caffeine increased over the four test days in the group maintained on caffeine, but pleasantness of the same drink fell significantly in the withdrawn group.

These data suggest that the ability of caffeine to reinforce changes in flavour liking are driven by the alleviation of withdrawal symptoms among habitual caffeine consumers and provide further support for the negative reinforcement theory.