FASTING, BREAKFAST, CAFFEINE AND CAFFEINE WITHDRAWAL: EFFECTS ON ALERTNESS, RECALL AND ENCODING

Andrew P. Smith PhD*

ABSTRACT

Background: Extensive research on the behavioural effects of consuming breakfast and caffeine has led to the identification of sensitive tests. It has been suggested that the effects of breakfast on memory and alertness may reflect removal of the negative effects of fasting. Similarly, it has been argued that beneficial behavioural effects of caffeine may be due to reversal of caffeine withdrawal. The aim of the present research was to examine these mechanisms using tests which are known to be sensitive to the effects of breakfast and caffeine. Methods: The present study examined the effects of fasting and caffeine withdrawal over the course of an 8 hour period during the day. The participants were 65 males and 65 females, age range 18-30 years, mean age 23.5 years. Participants carried out a baseline test session and were then given breakfast cereal and caffeinated coffee (100 mg caffeine). Volunteers were then assigned to groups formed by combining fasting (fast/no fast) and caffeine withdrawal conditions (withdrawn/non-withdrawn). The effects of fasting and withdrawal were tested 8 hours after breakfast. Following this test volunteers were given caffeine (100 mg) or placebo, and breakfast cereal or no cereal. A final test session was completed an hour later. Results: The results showed that fasting was associated with reduced pre-test alertness and poorer recall of a list of words. Caffeine withdrawal had no significant effects on tests of post-task alertness and encoding. In the final session, caffeine increased post-task alertness and encoding of new information. This was observed in both withdrawn and non-withdrawn volunteers. Breakfast cereal increased pre-task alertness in both those who had fasted and those who had not. However, breakfast cereal only improved recall in the fasted group. Conclusions: Use of sensitive tests demonstrated behavioural effects of breakfast cereal and caffeine. Fasting led to reduced alertness and poorer recall and the effect on memory was removed by consuming cereal. The effects of caffeine were observed in both withdrawn and non-withdrawn volunteers.

Keywords: Fasting; Caffeine; Breakfast Cereal; Caffeine withdrawal; Encoding; Alertness; Free recall.