Chewing gum and cognitive performance: a case
of a functional food with function but no food?
Human Cognitive Neuroscience Unit, Division of Psychology, Northumbria University, Newcastle upon Tyne NE1 8ST, UK
Received 10 June 2004; revised 15 July 2004; accepted 26 July 2004
Recent reports suggest that enhancement of memory performance while chewing gum is a fairly robust phenomenon. The processes
underlying the effect are not known, but may involve glucose delivery, context-dependent effects and arousal mechanisms amongst others.
This brief commentary outlines the main findings from these studies and raises some issues regarding interpretation, methodology and future
q 2004 Elsevier Ltd. All rights reserved.
Keywords: Chewing gum; Functional food; Memory; Attention; Cognitive performance
There have recently been several reports of studies into
potential cognitive enhancement by the chewing of gum, a
phenomenon first reported in this journal by Wilkinson,
Scholey, and Wesnes (2002). In that experiment we
compared cognitive performance in groups who chewed
sugar-free gum, ‘sham chewed’ (mimicking mastication in
the absence of gum), or sat quietly: chewing significantly
improved performance on standardised tests of working
memory and episodic memory (immediate and delayed
word recall), but not attention. Two new papers (Baker,
Bezance, Zellaby, & Aggleton, 2004; Stephens & Tunney,
2004) support the original finding and extend our
understanding of the mechanisms contributing to the effect.
However, a recent paper by Tucha, Mecklinger, Maier,
Hammerl, and Lange (2004), also in Appetite, reported no
effects of gum chewing on memory, although they did find
positive and negative effects of chewing gum on specific
aspects of attention. This present comment considers
some possible reasons behind these discrepancies and
examines other methodological issues pertaining to the
further glucose uptake into metabolically active cells. Since
glucose can itself improve aspects of memory functioning, it
was hypothesised that if the chewing effect was mediated by
the above process then there may be additive or even
synergistic effects of gum chewing and glucose in combi-
nation, especially in glucose-sensitive tasks. Using a within-
subjects design where subjects were tested under four
conditions (one factor was chewing gum vs. sucking a
mint; the other was ingesting a glucose load vs. water),
Stephens and Tunney confirmed that chewing improves
immediate and delayed recall. There was also evidence of
gum and glucose having additive effects on tests of working
memory and one attentional measure. Since Wilkinson et al.
(2002) found no attentional effects, this finding neatly
reinforces the need for assessing multiple aspects of
cognitive domains when such research in its infancy.
From the data of Stephens and Tunney it could be
suggested that, unlike working memory and immediate
secondary memory, longer term memory enhancement by
chewing gum is independent of modulation of glucose
delivery and alternative hypotheses need to be tested. These
include the possibility of activation of neural circuits shared
by chewing and memory formation. The latter may include
0195-6663/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
Appetite 43 (2004) 215–216
E-mail address: email@example.com.
forebrain regions identified as being activated during
chewing relative to sham chewing (Takada & Miyamoto,
2004), although this relationship remains to be delineated.
An alternative possibility is that chewing gum increases
arousal (Wilkinson and colleagues reported increased heart
rate in the gum chewing group) at levels which selectively
optimise memory performance.
Baker et al. (2004) examined a different aspect of the
phenomenon, namely the possibility that chewing gum can
aid memory via context-dependent effects. In two studies
they again found that chewing gum can improve recall of
verbal material (word lists), they also found that this may be
partially (though not completely) due to context effects.
That is, switching from chewing to not chewing between
learning and recall 24 h later diminished the chewing
enhancement effect to some degree. In a second experiment
they compared chewing with sucking gum using a similar
paradigm and found that flavour alone was sufficient to
account for some of the context effects of gum chewing.
Surprisingly it appears that Baker et al.’s Experiment 2
may be the first time that memory effects of flavour
‘context’ have been examined experimentally at both
learning and recall. This is an extremely interesting finding
given the literature on Proustian memory, so-called because
of an incident, described by the author Marcel Proust, in
which a particular flavour triggers vivid childhood mem-
ories. The possibility of manipulating flavours at learning
and recall, whether in the context of chewing or not, raises
exciting pure and applied research possibilities examining
the role of flavour in memory. The most relevant work in
this area has focused on the context-dependent effects of
smell which clearly plays a part in the orosensory properties
of food, presumably including during gum chewing.
Nevertheless it is also clear from Baker et al.’s results that
the act of mastication also plays a part both in the context-
dependent effects of chewing and in the absolute
enhancement of memory associated with chewing gum.
Interestingly, the Stephens and Tunney study used sucking a
mint ‘to dissolution’ prior to the battery as a control for
chewing. Thus, the improvements from chewing gum
(which occurred throughout the battery) in that study may
have been due to context effects. It would be interesting to
replicate these studies using flavoured gum, unflavoured
gum, flavour alone and a quiet control in order to
disentangle the relative contribution of these factors to
enhancement of memory by the chewing of gum.
Using an impressive range of controls (chewing non-
flavoured gum, sham chewing and a quiet control), Tucha
et al. (2004) found no evidence of improved memory from
chewing spearmint gum. Nevertheless, in two crossover
studies Tucha and colleagues report modulation of atten-
tional performance by chewing gum, including improved
performance in latter stages of a sustained attention task in
the group who chewed flavoured gum. However, this should
be viewed in the context of reduced ‘tonic’ alertness in both
Experiments and poorer ‘phasic’ attention in Experiment 2.
The reasons for these differences are unknown, and the lack
of detail regarding the timing and control of stimuli in
Tucha et al.’s brief communication preclude direct
comparisons with other studies. However, they did use
auditory presentation of word lists which may have affected
performance (Stephens and Tunney also used auditory
presentation, but assessed recall over several trials).
Additionally Tucha and colleagues used a different brand
of gum from the other studies and it is possible that
differences in chewing resistance may produce different
neurocognitive effects. For example, it is known that gums
of different consistency produced different patterns of
cerebral blood flow and heart rate changes (Suzuki et al.,
1994). It may be relevant that Tucha et al. did not find
the previously reported elevated heart rates associated
A common theme in cognitive nutraceutical research is
the extent to which positive effects reflect absolute
enhancement or restoration of a deficit (for example,
positive cognitive effects of glucose or caffeine may be
more readily observed following overnight deprivation).
Clearly, it is unlikely that an individual is in a state of
‘chewing deprivation’; so that is not an issue here. This does
lead to another point for consideration: to what extent can
sugar-free gum be classed as a nutraceutical? The latter is
strictly defined as any substance that is a food or a part of a
food which provides medical or health benefits. The term is
used more loosely to describe so-called ‘functional foods’
whose administration provides something other than simple
nutritional load. Clearly sugar-free gum has no nutritional
value as such, ironically making it theoretically more
similar to a pharmaceutical than a nutraceutical, despite
apparently sharing more elements with feeding than with
Baker, J. R., Bezance, J. B., Zellaby, E., & Aggleton, J. P. (2004). Chewing
gum can produce context-dependent effects upon memory. Appetite,
doi: 10.1016/j.appet.2004.06.004, this issue.
Stephens, R., & Tunney, R. J. (2004). Role of glucose in chewing
gum-related facilitation of cognitive function. Appetite, doi: 10.1016/
j.appet.2004.07.006, this issue.
Suzuki, M., Ishiyama, I., Takiguchi, T., Ishikawa, H., Suzuki, Y., & Sato,
Y. (1994). Effects of gum hardness on the response of common carotid
blood flow volume, oxygen uptake, heart rate and blood pressure to
gum-chewing. Journal of Mastication and Health Sciences, 4, 9–20.
Takada, T., & Miyamoto, T. (2004). A fronto-parietal network for chewing
of gum: a study on human subjects with functional magnetic resonance
imaging. Neuroscience Letters, 360, 137–140.
Tucha, O., Mecklinger, L., Maier, K., Hammerl, M., & Lange, K. W.
(2004). Chewing gum differentially affects aspects of attention in
healthy subjects. Appetite, 42, 327–329.
Wilkinson, L., Scholey, A., & Wesnes, K. (2002).Chewing gum selectively
improves aspects of memory in healthy volunteers. Appetite, 38,
A. Scholey / Appetite 43 (2004) 215–216 216