Ruminating & Masticating to Help in Concentrating & Focusing on the Job at Hand

Effects of Chewing Gum are Inconclusive Until Now

As children, many of us never had the habit of chewing our food and then swallowing it. Though the advent of kids’ channels and YouTube subscriptions is only recent, we did have our share of Shakthimaan, Little Krishna, Tom & Jerry and our sweet little games played with close friends to quickly get over the ritual of eating food. Mom used to feed the rice/roti into our mouth and even before she could pick up another handful our mouths would be wide open just because we never chewed our food but only swallowed it. Growing up, we decided to take better care of our health and started chewing the food but once again with competitive education, job pressure and lack of time, as adults too our intention to chew has disappeared into thin air. We almost gobble up the food during breakfast (if in case we eat it!) or munch on a burger during lunch in such a hurry that we don’t even remember whether we chewed or swallowed!

Chewing is the very first step in eating. It enables the food to break down into smaller particles, mix with saliva and finally swallow it down the food pipe. While crushing food to aid in easy digestion was assumed to be the core function of chewing, we now have studies showing that chewing in fact is associated with brain functions too! While we might be surprised by this, the link between chewing and cognitive functions was established long ago, as early as the 1930s when it was discovered that chewing helped reduce stress and also improve cognitive performance. Since then there have been studies trying to relate chewing to attention, memory retention and other cognition-related functions but results have been inconclusive. Hypothesizing that chewing does improve attention different studies were reviewed and their results analyzed.

Studies that reported effects of chewing in healthy adults and children but not in elderly population and those that probed into the efficiency of attention, alertness, vigilance and executive control compared with no gum chewing conditions were considered. 22 articles were eligible and the following variables were noted for each of them:
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1. Cognitive tests and psychological rating scales
2. Chewing objects
3. Summary of results compared with nonchewing condition unless stated
4. Attributes of effects on attention
   
   

Results from different studies show different advantages and those include:

1. Alertness and hedonic tone apart from intelligence were improved in one study but there were no improvements in memory
2. Two mechanisms were activated due to chewing-mobilization of energetic resources (particularly facial muscles) and neurotransmitter function (5-HT descending inhibitory pathway).
3. Chewing improved alertness, reduced stress, anxiety and saliva cortisol. It was believed that chewing improved cognitive skills due to decrease in mental stress
4. Taste and odor can influence brain activation during chewing in sensory, cognitive and motivational processes rather than in motor control though some studies did show effects on attention being linked to tasteless and odorless gum
5. A majority of the studies did show that chewing exerts a positive effect on attention, especially sustained attention besides improving mood and giving stress relief. But, these benefits did not last beyond 30 minutes after chewing. So, chewing can be taken as a reliable way to improve cognitive function without taxing the individual physically or mentally but with the condition that the gum is not sugar-laden, calorie-laden and additive-laden.
   
   

Effect of Chewing on Hippocampus-dependent Cognitive Function
Cognition is inversely proportional to age. As we grow old, psychological, neurobiological and social factors impact our ability to think and keep information and dementia rates also prevail in higher numbers. Mastication and the number of teeth in an individual too seem to affect cognitive functions. The number of teeth decrease in elderly population and this leads to oral health problems which in turn affects the general health of the person. The ability to chew properly remains utmost important in people to safeguard their general health, oral health and cognitive abilities. Hippocampus is the part of the brain that helps in forming and retrieving memories. Improper/impaired mastication causes functional alterations of the hippocampus while proper mastication helps in promoting hippocampus function. Let’s understand how mastication and the hippocampus are related to each other.

Mastication is the first step in digestion where the tongue, facial and jaw muscles act in coordination to crush the food and prepare it for swallowing. The bones (maxilla and mandible), muscles, teeth and soft tissues (tongue, lips and cheek) are involved in mastication. We have animal studies showing that blood oxygen levels in the prefrontal cortex and hippocampus are increased by mastication and decrease in mastication either due to extraction or reduction in molars can inhibit memory and learning. We do have several human studies showing that chewing is effective for preserving hippocampus function that gradually deteriorates with ageing. Even sucking a small piece of a sugar-free gum was linked to better cognitive performance. Chewing increases the flow of blood to the muscles and decreases risks of cognitive decline. Mastication during stressful situations attenuates stress-induced impairments of plasticity in the hippocampus.

Gum Chewing & Cognition
We do have studies both supporting and denying the advantageous effects of gum chewing on cognitive abilities. 26 studies were filtered and their results were thoroughly analyzed.

Effects of Gum Chewing on Cognition

Immediate & Delayed Memory: Immediate recall refers to retrieval of information immediately after learning while delayed recall refers to retrieval of information after a prolonged period (several minutes to days or even longer) of learning. In a study by Wilkinson et al, it was found that chewing a piece of sugar-free gum improved both immediate and delayed (in less than an hour) recall of previously learned words (15 words). Baker et al tried to replicate this research on 15 words but their results showed that they did not find any effect in immediate recall but chewing gum posed beneficial effects on delayed recall even after a delay of 24 hours. Tucha and colleagues performed two tests-one for attention span and another for delayed and immediate recall but results failed to show anything positive for immediate or delayed recall. Miles and Johnson too conducted the same studies and in fact found detrimental effects of gum chewing on immediate and delayed recall. Kozlov and et performed well-controlled studies to show the impaired effect of chewing gums on immediate recall. The authors could confirm the detrimental effect of gums and also could confirm that the results remained the same regardless of the mode of assessment (word, letters or numbers). While totally 16 studies examined the effect of chewing gum on immediate and delayed recall, 2 studies found beneficial results, 6 showed positive effects on delayed recall, 1 showed detrimental effect on immediate and delayed recall, 2 showed negative effects on immediate recall, 2 failed to find any effect on both, 4 found no positive/negative effect on immediate recall and four others failed to find any effect on delayed recall.

Context-dependent Effects of Gum Chewing on Memory
‘Context’ refers to the impact the environment or internal state of an individual has on information acquisition and retrieval. It was generally seen that recall of information was better when the context during recall was similar to the context that existed during learning. Baker and et found that a change of context during learning and retrieval produced adverse effects on recall. While Johnson and Miles could not produce any results on context-dependent benefits on delayed recall and in another study even proved that those who did not chew gum during both learning and recall performed better in comparison to those who chewed gum. Two studies found that chewing gum could provoke context-dependent effects on long-term memory while four studies could not find any link. So, context-dependent effect shows that it was not that chewing the gum gave better results. Maintaining the same context while learning and retrieving (chewing the gum or not) enabled better outcomes than those participants performing in inconsistent context conditions.

Attention
Attention is critical for cognitive and emotional functioning. One study showed that gum chewing was negatively associated with alertness and two studies found that chewing was in no way associated with linked to gum chewing. Though it was seen that alertness levels increased when gum was chewed prior to testing. Gum chewing though had a positive impact on sustained attention. Taenzer and et found that kids aged 8-9 years performed badly on a sustained attention task than children who did not chew gums. While this result was observed during the first 12 minutes of the test, during the last four minutes children in the no-gum category were outperformed by those in the gum-condition showing that gum chewing did have a beneficial effect on sustained attention.
Stephens and Tunney witnessed improved results in selective attention when participants chewed gums. Shifting of attention was actually impaired due to gum chewing in one study but another study saw no differences in results. Totally, 12 studies focused on gum chewing: 4 of them found that gum chewing improved sustained/selective attention, 4 showed detrimental effects of gum chewing on selective attention, alertness and shifting and sustained attention, five of them failed to prove that gum chewing affected alertness, sustained attention, selective attention or divided attention.

Intellectual functioning, executive functions and spatial skills too showed contradictory effects when studies were conducted as some supported gum chewing while others condemned gum chewing based on their study results. One thing is clear, gum chewing does affect cognition but what has to be confirmed is whether it does have 100% positive effects or detrimental effects on the person chewing it.

Worldwide, the number of people chewing gums are high-in a survey of American undergraduates almost 87% reported chewing gums at least occasionally, 61% respondents in a UK survey reported that they were of the habit of chewing gums and in general too, people chew gums to overcome stress, focus better and hide away their anxiety but there are a number of factors through which chewing gum might affect stress, alertness and cognition including the duration for which you chew the gum. So, while it is ok to occasionally chew a gum that’s sugar-free regularly indulging in this habit is not recommended until we have stronger evidences proving their benefits 100%.
 
References
Chewing & Attention: A Positive Effect on Sustained Attention: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4449948/

Chewing Maintains hippocampus-dependent cognitive function: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4466515/

Gum Chewing & Cognition-An Overview: https://file.scirp.org/pdf/NM20120300003_99040712.pdf
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A Review of Evidences that Chewing Gum Affects Stress, Alertness & Cognition: http://psych.cf.ac.uk/home2/smith/206.pdf